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Aflvcroigl... 0.4.191.‘l(9lll: 4 . . ‘ . .11!!!) «51.1.5.3: ‘. . .ILDIOI .v‘ltl).v€..u . . . 4 .. 1". r ‘f. ‘ ..Iuv A tax! ‘ I ' ' it II 121? $3; o ,‘c o}; L.» ‘ Q‘I‘HQESES’IQM nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn \ \x‘l' ' 31293 00605 0649 LIBRARY Michigan Stat. University This is to certify that the dissertation entitled FACTORS AFFECTING FEED INTAKE IN LACTATING SONS AND THE EFFECT OF FEED INTAKE IN EXCESS OF AD LIBITUM 0N LACTATION PERFORMANCE IN MULTIPAROUS SONS presented by Paul Douglas Matzat has been accepted towards fulfillment of the requirements for PhD; degree in Wee a Major professé'; ; ; MS U is an Affirmative Action/Equal Opportunity Institution 042771 Date_May_14+_199.0__ PLACE N RETURN BOX to remove thle checkout from your record. TO AVG. FINES mum on or before due due. DATE DUE DATE DUE DATE DUE F—fim MSU Is An Affirmative Action/Equal Opponunlty Institution FACTORS AFFECTING FEED INTAKE IN LACTATING SOWS AND THE EFFECT OF FEED INTAKE IN EXCESS OF AD LIBITUM ON LACTATION PERFORMANCE IN MULTIPAROUS SOWS By Paul Douglas Matzat A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Animal Science 1990 (oochqicbi ABSTRACT FACTORS AFFECTING FEED INTAKE IN LACTATING SOWS AND THE EFFECT OF FEED INTAKE IN EXCESS OF AD LIBITUM ON LACTATION PERFORMANCE IN MULTIPAROUS SOWS By Paul Douglas Matzat Many environmental factors have been identified that .influence feed intake of lactating sows. An experiment was conducted to determine the influence of various environmental factors (”1 daily feed intake» of lactating sows. In addition, techniques were developed to allow feeding lactating sows in excess of ad libitum and measure sow and litter response in lactation. In Experiment I, 217 sows of various parities were used to determine environmental influences on tdaily lactation feed intake. Sows were fed ad libitum and daily feed intake was measured. Measured variables were daily rectal temperature, daily ambient temperature, weekly changes in sow' weight, sow backfat and litter weight. Sows were categorized by parity, litter size, breed and season of the year at farrowing. Regression analysis described daily feed intake with a minimum degree of accuracy (R2=.38). Effects of elevated ambient temperature and body fatness of the sow at farrowing was associated with reduced feed intake in lactation. Litter size and litter weight gain were associated with variations in daily feed intake of_1actating sows. In Experiment II, a technique was developed to gastrically cannulate pregnant sows at day 85 of gestation. The technique did not affect litter size and piglet survivability at farrowing. Cannulated sows were fed entirely through the cannula with no detremental effects on lactation performance. In Experiment III, 29 sows were divided into three groups of non-cannulated sows (NC), cannulated control (CC), and cannulated superal imentated sows (SA) with daily metabolizable energy (ME) intakes of 19, 21 and 28 Mcal of ME/day, respectively. SA sows gained weight and backfat in lactation, whereas NC and. CC sows lost both ‘weight and backfat in lactation. SA sows had greater milk yields and litter weight gain as compared to NC and CC sows. Milk fat levels were greater in week 4 of lactation for SA sows as compared to NC and CC sows. In conclusion, daily feed intake of lactating sows is influenced by ambient temperature, sow backfat at farrowing, litter size and litter weight gain. Farrowing and lactation performance of sows is unaffected by gastric cannulation. Digestion and absorption of nutrients fed in excess of ad libitum is not limiting in lactating sows. Sow and litter performance in lactation is influenced by feed consumption level. ACKNOWLEDGMENTS Many people helped in the completion of this graduate degree. Dr. M.G. Hogberg gave me the opportunity to attend Michigan State University and pursue graduate studies. The opportunity to manage the Michigan State University Swine Teaching and Research Farm and do graduate work simultaneously was a unique and gratifying experience. This combination allowed me to obtain a broad perspective of new developments in biotechnology as well as a valuable understanding of day to day problems faced by pork producers . I was al lowed the opportunity to convey this information to both producers and students. For the training, interaction and advice I will be constantly grateful to my major professor Dr. Hogberg. Members of my guidance committee were Dr. E.R. Miller, Dr. R.L. Fogwell, Dr. B.K. Thacker and Dr. W.T. Magee. Each of these individuals helped shape my direction in both graduate studies and research endeavors. Each was extremely open and offered much advice and guidance. Thank you for your time and effort. The laboratory segment of this endeavor was made much easier and even enjoyable by Dr. P.K. Ku with technical help from Sharon DeBar and Ann Duncan. iv TABLE LIST OF TABLES . . . . . LIST OF FIGURES. . . . . INTRODUCTION . . . . . . REVIEW OF LITERATURE . . Introduction. . . . . OF CONTENTS Factors Affecting Feed In ake Feeding during pregnancy Parity and metabolic body size . . . . . . Ambient temperature and relative humidity. Season . . . . . . Litter size and milk yield Stage of lactation . Genetics . . . . . Health and body temperature Feeding frequency. Feed flavor. . . . Feed quality . . . Energy density of diet Predicting feed intake in lactating sows Summary. . . . . . Energy and Nitrogen Balance in Lactating Sows Energetics of lactation. Milk production. . in Lactating Sows Energy and nitrogen balance of the sow in lactation. . . . . Summary. . . . . . Physiological Factors Affecting Feed Intake Preabsorptive controls of food intake. . Postabsorptive controls of food intake . Feeding level effects on blood borne metabolites and insulin. Feeding in excess of ad libitum. . . . . . Feeding level effects on ovarian function. Summary. . . . . . Conclusions . . . . . vi Page viii EXPERIMENT I - Factors Affecting Daily Feed Intake in Lactating sows . . . . . Introduction. . . . . . . . Materials and Methods . . . Animal care and housing. Statistical analysis . Results . . . . . . . . . Discussion. . . . . . . . Conclusions . . . . . . . EXPERIMENT II - Gastric Cannulation of Pregnant Sows. . . . . . . . . . . . . . Introduction. . . . . . . . . Materials and Methods . . . . Fabrication of the cannula Surgical procedure . . . . Results . . . . . . . . . . . Discussion. . . . . . . . . . EXPERIMENT III - Effects of Feeding Lactating Sows in Excess of Ad Libitum on Lactation Performance and Nutrient Balance. . Introduction. . . . . . . . . . . Materials and Methods . . . . Animal care and management Laboratory determinations. Statistical analysis . . . Results . . . . . . . . . Discussion. . . . . . . . Conclusions . . . . . . . GENERAL DISCUSSION . . . . . . . . . . . . . . . . Summary and Conclusions . . . . . . . . . . . . LIST OF REFERENCES 0 O O O O O O O O O O O O O O 0 vii 107 107 108 108 115 117 118 137 142 144 150 152 Table 1. Table 2. Table 3. Table 4. Table 5. Table 6. Table 7. Table 8. Table 9. Table 10. Table 11. LIST OF TABLES Daily Milk Energy Yield per Metabolic Body 8126. O O O O O O O 0 O 0 O O O 0 O O O O 0 Composition and Calculated Analysis of Diets O 0 O O O O 0 O O O O 0 O O O O O 0 0 Correlation of Daily Lactation Feed Intake and Various Environmental Factors . . . . . Mean Lactation Feed Intake. . . . . . . . . Relationship of Mean Daily High Temperature in Lactation with Mean Daily Feed Intake in Lactating Sows. . . . . . . . . . . . . . . Relationship of Mean Daily Low Temperature in Lactation with Mean Daily Feed Intake in Lactating Sows . . . . . . . . . . . . . Relationship of Sows Exposed to Hot Daily High Temperature (>27'C) and either Warm (>24'C) or Cool (<24'C) Daily Low Temperature with Mean Daily Feed Intake of Lactating Sows. . . . . . . . . . . . . . . Relationship of Season of the Year with Mean Daily Feed Intake of Lactating Sows. . Relationship of Sow Backfat Depth at Farrowing and Mean Daily Feed Intake in Lactating Sows. . . . . . . . . . . . . . . Relationship of Sow Rectal Temperature on Day 1 of Lactation with Mean Daily Feed Intake in Week 1 and in the Entire Lactation . . . . . . . . . . . . . . . . . Relationship of Feed Intake on Day 1 of Lactation with Mean Daily Feed Intake of Lactating Sows. . . . . . . . . . . . . . . viii Page 32 59 62 67 70 71 73 74 75 77 78 Table Table Table Table Table Table Table Table Table Table Table 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. Relationship of Sow Parity and Mean Daily Feed Intake of Lactating Sows . . . . . . Relationship of Number of Pigs Weaned and Mean Daily Feed Intake of Lactating Sows. Relationship of 21 Day Litter Weight with Mean Daily Feed Intake of Lactating Sows. Relationship of Total Feed Consume in Lactation with Various Sow and Litter Performance Criterion . . . . . . . . . . Effects of Cannula Placement in Pregnant Sows on Reproduction and Lactation Performance . . . . . . . . . . . . . . . Composition and Calculated Analysis of Diets O O O O 0 O O O O O I O O 0 I I 0 0 Effects of Feeding Level on Lactation Performance . . . . . . . . . . . . . . . Effect of Feeding Level on Milk Yield and Composition . . . . . . . . . . . . . . . Effect of Feeding Level and Stage of Lactation on Milk Yield and Milk comPOSition O O O O I O O O O O O O O O 0 Concentration of Insulin and Selected Metabolites in Blood During Lactation . . Energy and Nitrogen Balance of Sows in Early or Late Lactation . . . . . . . . . ix Page 80 81 83 84 105 110 119 126 131 132 136 Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Figure 8. Figure 9. Figure 10. Figure 11. LIST OF FIGURES Relationship of Various Environment, Nutrition, Management Genetic and Health Factors with Feeding Level in Lactating Sows. . . . . . . . . . . . . . . . . . . Mean Daily Feed Intake of Sows in 28d Lactation 0 O O O O O O O O I O O O O O 0 .Relationship of Daily High Ambient Temperature and Daily Feed Intake in Lactating sows O O O O 0 O O O 0 O O O O 0 Relationship of Daily Low Ambient Temperature and Daily Feed Intake in Lactating Sows . . . . . . . . . . . . Relationship of Sows Exposed to Hot Daily High Temperature (>27'C) and either Warm (224'0) or Cool (<24'C) Daily Low Temperature and Daily Feed Intake in Lactation . . . . . . . . . . . . . . . . Relationship of Season and Daily Feed Intake in Lactating Sows. . . . . . . . . Relationship of Sow Backfat Depth at Farrowing on Daily Feed Intake in Lactation . . . . . . . . . . . . . . . . Relationship of Sow Rectal Temperature on Day 1 of Lactation and Daily Feed Intake in Week 1 of Lactation. . . . . . . . . . Relationship of Feed Intake on Day 1 of Lactation and Daily Feed Intake in Lactating Sows. . . . . . . . . . . . . . Relationship of Sow Parity and Daily Feed Intake in Lactation. . . . . . . . . . . Relationship of Number of Pigs Weaned and Daily Feed Intake of Lactating Sows. . . X Page 24 68 7O 71 73 74 75 77 78 80 81 Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. Relationship of Litter Weight at d 21 of Lactation and Daily Feed Intake of Lactating Sows. . . . . . . . . . . . . . Relationship of Total 28d Lactation Feed Intake and Daily Feed Consumption in Lactating Sows. . . . . . . . . . . . . . Relationship of Total 28d Lactation Feed Intake and Sow Weight in Lactation. . . . Relationship of Total 28d Lactation Feed Intake and Sow Backfat Depth in Lactation . . . . . . . . . . . . . . . . Relationship of Total 28d Lactation Feed Intake and Litter Weight in Lactation . . Relationship of Ambient Temperature and Mean Daily Intake in Lactating Sows . . . Relationship of Sow Backfat Depth at Farrowing and Mean Daily Feed Intake in Lactating sows O O O O O O O O O 0 O 0 O 0 Relationship of Sow Weight on d1 of Lactation and Mean Daily Feed Intake in Lactating Sows. . . . . . . . . . . . . . Relationship of Litter Size Weaned and Mean Daily Feed Intake in Lactating Sows. Relationship of Litter Weight at d21 of Lactation and Mean Daily Feed Intake in Lactating Sows. . . . . . . . . . . . . . Mean Daily Feed Intake of NC, CC, and SA Sows in Lactation. . . . . . . . . . . . Mean Weight of NC, CC and SA Sows in Lactation 0 O 0 O O O 0 O O 0 0 O O O O 0 Mean Weight Change of NC, CC and SA Sows in Lactation . . . . . . . . . . . . . . Mean Last-rib Backfat of NC, CC and SA Sows in Lactation. . . . . . . . . . . . Mean Last-rib Backfat Change of NC, CC and SA Sows in Lactation. . . . . . . . . xi Page 83 85 85 87 87 89 91 93 95 95 121 122 122 123 123 Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. Mean Litter Weight of NC, CC and SA Sows in Lactation. 0 O O O O O O 0 O O 0 O O 0 Mean Litter Weight Change of NC, CC and SA Sows in Lactation. . . . . . . . . . . Mean Weekly Milk Yield as Measured by the Weigh-suckle-weigh Method of NC, CC and SA Sows in Lactation. . . . . . . . . . . Mean Milk Dry Matter of NC, CC and SA Sows Measured Weekly in Lactation . . . . Mean Milk Ash of NC, CC and SA Sows Measured Weekly in Lactation. . . . . . . Mean Milk Crude Protein of NC, CC and SA Sows Measured Weekly in Lactation . . . . Mean Milk Lactose of NC, CC and SA Sows Measured Weekly in Lactation. . . . . . . Mean Milk Lipids of NC, CC and SA Sows Measured Weekly in Lactation. . . . . . . Mean Milk Gross Energy of NC, CC and SA Sows Measured Weekly,in Lactation . . . . Mean Serum Insulin Concentrations of NC, CC and SA Sows Measured Weekly in Lactation . . . . . . . . . . . . . . . . Mean Plasma Glucose Concentrations of NC, CC and SA Sows Measured Weekly in Lactation . . . . . . . . . . . . . . . . Mean Blood Urea Nitrogen Concentrations of NC, CC and SA Sows Measured Weekly in Lactation 0 O I O O I O O O O O O O O O 0 Mean Blood Non-esterified Fatty Acid Concentrations of NC, CC and SA Sows Measured Weekly in Lactation . . . . . . xii Page 125 125 126 128 128 129 129 130 130 133 133 135 135 INTRODUCTION Maximizing the profitability and efficiency of a pork production enterprise is the goal of most pork producers. Certainly management of a swine production enterprise can greatly affect the net return on investment. Various measures of the success of a management scheme have been developed. The bottom line or the overall profitability of a production unit is the most often used measure of success. However, this does not allow the producer to evaluate portions of the production cycle. Segmentation of the pigs life cycle in a pork production unit allows analysis of each phase of production, thus enabling the producer to find his strengths and weaknesses. Many widely used measures of success of a management plan and efficiency of production deal with the reproductive capability of the herd. Measures such as pigs per sow per year, pigs weaned per farrowing crate per year or pigs weaned per litter are commonly used to compare and monitor overall productivity. Interactions of nutrition, management, environment, genetics and health cause a wide variation of reproduction efficiencies. The ability of a sow to mate, conceive and farrow a large healthy litter of pigs is foremost in the effort to attain high reproductive standards. However, after parturition an equally important task is to produce large quantities of milk, wean a large, uniform litter, return to estrus and subsequently conceive a large litter of pigs is required of the sows. Various factors that affect reproductive efficiency have been documented. It is apparent that nutrition has a large direct and indirect affect on each phase of reproduction. In addition, improper nutrition in one phase of the reproductive cycle affects subsequent phases. Generous feeding levels in gestation will result in excess body weight gain and body fat accretion during that period (Baker et al., 1968; Whittemore et al., 1980; Close et al., 1984). Gestation feeding levels above 6 Mcal (mega- calories) metabolizable energy (ME) have shown little benefit to reproductive performance of sows (ABC, 1981; Whittemore et al., 1984; Aherne and Kirkwood, 1985; NRC, 1988). Other than specific animals that may be extremely thin from a previous lactation, feeding levels above 6 Mcal ME will simply increase gestation sow weight and body fat gain. It has been well documented that large gains in body weight and body fat during gestation result in decreased feed intake during the following lactation (Salmon-Legagneur and Rerat, 1962; Baker, et al., 1968; Lodge, 1972; Brooks and Smith, 1980; Seerley and Ewan, 1983; O’Grady et al., 1985). Speer (1982) showed that feeding sows’ low levels of protein and protein free diets during gestation did not adversely affect embryo survival or fetal development. Studies where low or restricted energy intake in gestating sows were observed minimal effects on embryo mortality or fetal development occured(Baker et al., 1968; Elliot and Lodge, 1977; Close and Cole, 1986; Pond, et al., 1987). However, restricting both energy and 'protein resulted in reduced piglet birth weight. Restricting protein or energy through gestation and lactation will reduce the number of sows returning to estrus at weaning and increase length of time from weaning to estrus (Cole, 1982; Reese et al. 1982 ab; Close and Cole 1986), ovulation rate and subsequent litter size (Holden et al., 1968; Hovell and MacPherson 1977; Aherne and Kirkwood, 1985; Kirkwood et al., 1987 ab). Varied sequences of nutrients in gestation and lactation can affect lactation feed intake and lactation performance. Improperly balanced rations can negatively affect feed intake in lactating sows (Mahan and Mangan, 1975; Hughes, et al., 1984; Kirkwood et al., 1987 ab). Feeding level in lactation affects milk yield and thus litter weight gain (Verstegen, et al., 1984; Noblet and Etienne, 1986). In addition, restricted feeding in lactation resulted in a greater loss of body weight and body fat in lactating sows (Noblet and Etienne, 1986) as well as reduced embryo survivability in the subsequent gestation (Kirkwood et al. 1987 ab). Few studies are available that look at long term effects of dietary energy, protein, vitamin and mineral levels in gestation and lactation on sow reproductive performance and sow longevity (Kirkwood et al., 4 1988). Weight gain in gestation and recommended feeding levels in lactation are usually made for the ”average” sow. However, for sows that are highly productive, nutrient requirements will not be met by feeding recommended levels. Although sows may be offered all the feed they will consume, nutrient intake often does not match nutrient requirements. O’Grady et al. (1985) reviewed factors such as fatness, parity of sow, litter size, ambient temperature and genetics that affect voluntary feed intake in lactating sows. Many factors, such as temperature (Lynch, 1977), season (O’Grady, et al., 1985; Britt, 1986), form of diet (O’Grady and Lynch, 1978; Moser, 1984) lighting (Mabry et al., 1982; Stevenson et al., 1983), length of lactation period (Mahan, 1977; O’Grady' et al., 1985), that. may affect feed intake in lactation are related to the management practices employed. Additional factors, such as genetics (Pond et al., 1981; O’Grady et al., 1985), parity (Mahan, 1979; Britt, 1986), litter size (ABC, 1981; Cole, 1982), metabolic body size (Verstegen, et al., 1985; Noblet and Etienne, 1986), all influence lactation feed intake. In addition, energy density of the diet (Moser, 1985; O’Grady et al., 1985) and protein and amino acid intake (Mahan and Grifo, 1975; O’Grady, 1985 Bendemuhl et al., 1987) affect feed intake level of sows during lactation. Current feeding practices for gestation and lactation suggest that sows should lose approximately 20 kg body weight over a 28 day lactation jperiod (Cole, 1982; Close and Cole, 1986; Whittmore, 1987). This strategy assumes that sows have satisfactory levels of energy stores in gestation and will maintain adequate feed intake in lactation. However, in situations where lactation feed intake is inhibited or lactation nutrient demands exceed nutrient intake, excess weight loss will occur. This will significantly reduce productivity and longevity of sows and reduce profit potential for the swine producer. Reduced productivity occurs because of extended anestrous after weaning (Reese et al., 1982 a; King, 1987; Kirkwood et al., 1987), impaired embryo survival in subsequent gestation (Hughes, et al., 1984; Kirkwood, et al. 1987), and a greater opportunity for injury (Harmon et al., 1974; Dagorn and Aumaitre, 1979; Maxson and Mahan, 1986) and therefore early culling from the herd (Whittemore, 1987). Return on investment in a sow is maximized by attaining six parities (Kroes and Van Male, 1979; O’Grady, 1985). The ability of the production unit manager to determine the correct feed intake level for individual sows in gestation and lactation is very important for animal longevity. But, the variation in production levels between animals, alternative housing and management schemes incorporated, and individual responses to various pratices within the herd make it difficult to specify feeding levels that apply to all animals. The goal of this learning process is to more fully understand various factors which influence feed intake in .lactating sows. A situation where nutrient intake does not 6 meet nutrient requirements especially relating to high producing sows will be examined. Environmental and physiological factors that influence appetite controls for both meal size and feeding frequency will be evaluated. Furthermore, if limitations on feed intake were removed, what impact would that have on lactating sow nutrient utilization and lactation performance. Ideally, this information will help improve understanding of care, feeding and management of sows in the swine breeding herd. REVIEW OF LITERATURE Introduction As the number of pork production units decline and the size of the remaining units expand, a common goal that these units share is to maximize sow productivity. The large dollar investment in facilities and equipment requires a level of management allowing little in the way of unproductive time or low production standards. Pork producers have become more aware of opportunities to use genetics in an attempt to maximize sow productivity. Sows with a high percentage of Yorkshire or Large White and Landrace are more prevalent in large commercial units due to superior reproductive capabilities such as large litter size and unsurpassed mothering ability. In addition, these sows generally produce large quantities of milk to wean a high percentage of those pigs farrowed at heavy weaning weights. The interaction of nutrition, environment, management, genetics and health becomes apparent in these highly specialized production facilities. In many cases, it is difficult to segregate differences between these factors. Management of the sow for optimum performance in the lactation phase involves many variables. Goals which producers strive to achieve are for sows to farrow large 8 litters uneventfully, resist infectious organisms postpartum, milk readily and voluminously and achieve maximum feed intake rapidly to maintain body condition and maximize milk yields. There is a complex interaction of factors that can either aid or impair the ability of the sow to attain these goals. If the sow is able to nurse a large number of piglets and reach maximum milk yield, in most cases she will be in a negative energy balance during lactation. Even with ad libitum feeding practices, sows with above average milking ability will catabolize body stores of fat, protein and minerals to maintain maximum milk production levels. Assuming the genotype of the sow is present to allow high standards of sow productivity, factors such as management, environment, nutrition and health can each, or in combination, weigh heavily on the sow’s ability to maintain productivity and longevity. As a result of reduced or inadequate feed intake in lactation, the sow loses body fat, protein and mineral stores. In addition, piglet performance may suffer as a result of reduced milk yields. Furthermore, if feed intake levels are severely reduced, subsequent reproductive performance of the sow may be impaired. A greater incidence of anestrous sows as well as an increase in days to return to estrus will be observed. Also, those sows that do return to estrus will likely have fewer eggs ovulated and a lower rate of embryo survivability in the subsequent parity. Sows that leave the farrowing house in a weakened, thin condition will also be more 9 likely to leave the breeding herd prematurely due to injury or infertility. This review will first, focus on the various factors affecting feed intake during lactation. This will include the effects of previous management of the animal as well as various management, nutritional, environmental, genetic and health aspects that influence feed intake in lactating sows. The second portion of the review will evaluate some of the physiological and metabolic changes that occur with various levels of feed intake in the lactating sow. E I SEE I' E I I l l . l I Ii 8 E l' I . The relationship between the amount of feed consumed during pregnancy and the amount of feed consumed during lactation. has been shown (Lodge, et al., 1961, 1966; Salmon-Legagneur and Rerat, 1962; Whittemore, 1987). Thirty years ago, sows were generally maintained in a fat body condition. Work done by Lodge (1959, 1961, 1966) and others in the late 1950 to early 1960 period indicated that sows fed 2 kg per day of a fortified grain based diet in gestation would perform as well as sows that were fed at a higher energy level. The concept of limit feeding sows in gestation ‘translated into substantial dollar savings for pork producers and was therefore readily accepted (Bowland 1968; Whittemore, 1987). With pressure to produce m 8: De fe 10 genetically leaner animals, feeding programs that maintain less body fat reserves and improved reproductive capacity of sows, the ”thin sow syndrome" was observed (MacLean, 1968, 1969). There is a relatively high correlation between feeding level in pregnant sows and gestation weight gain (ARC, 1981; Close et al. 1984; Aherne and Kirkwood, 1985). Body fatness levels are also related to level of feed intake in gestation (Whittemore, et al., 1980; Close, et al. 1984; Whittemore, 1987). As higher levels of weight gain and body fat are realized in gestation, lactation feed intake tends to be reduced (Salmon-Legagneur' and. Rerat, 1962; Lodge» at al. 1972; Cole, 1982; Aherne and Kirkwood, 1985). Other areas of reproductive efficiency can be affected by gestation feed intake as well. Piglet birth weight can be somewhat influenced by gestation feed intake. But, the correlation of gestation feed intake and piglet birth weight is reported to be one-half that of feed intake and sow weight gain (ARC, 1981; Aherne and Kirkwood, 1985). Litter size is relatively unaffected by gestation feeding levels (Whittemore, et al., 1984). Therefore, in an attempt to maximize feed intake in lactation, gestation body weight gains should be limited to approximately 25 kg per parity (Elsley et al., 1966; Whittemore, 1987). Feeding levels suggested for a 140 kg sow to attain 25 Kg weight gain in gestation is 6 kcal ME per day (Cole, 1982; Seerley and Ewan, 1983). Restricted feeding levels in gestation will stimulate an increase in 11 lactation feed intake (Baker, et al. 1968; ARC, 1981; Mullan and Williams, 1988). It appears that the phenomenon of increased weight and body fat gain in gestation causes a reduction in voluntary feed intake of other species as well. Several studies indicated that daily dry matter intake of dairy cows for the first 26 weeks of lactation varied with milk yield and body size. In sows with similar milk yields, those with a higher degree of body fat ate fewer pounds of feed in early lactation (Garnworthy and Topps, 1982; Neilson, et al. 1983). Cowan, et al. (1980) showed that body condition of ewes influenced feed intake in lactation as well. Ewes that were fatter tended to consume less feed in lactation. Various sequences of nutrients in gestation can affect feed intake in lactation. Normal levels of energy intake during the first 100 days of gestation followed by either a high or low level of energy did not affect sow lactation performance (Elliot and Lodge, 1977; Hillyer and Phillips, 1980; Pond et al., 1981; Cromwell et al., 1982; Barker and Cole 1988; Lee and Close, 1988). However, piglet glycogen levels were altered which could result in indirect effects on sow reproductive and lactation performance. Piglet survivability could be impacted as a result of low liver glycogen levels thus reducing suckling intensity, milk yield and therefore feed intake. When feed intake is increased for the last 25 days of gestation, it appears that sow weights as well as piglet birth weights increase. Adding 12 fat to the diet prior to parturition as a means of increasing the energy intake in sows has been described by Moser (1985). In some cases piglet survivability is improved, and the fat level of colostrum and early lactation milk were elevated. Lipid addition to the diet did not affect piglet body fat or liver glycogen content (Seerley, 1984). However, it has been reported that in cases where preweaning piglet survivability is low, adding fat to the diet 8-10 days prior to parturition will aid in improving piglet survivability rates (Pettigrew, 1981; Moser, 1985). Feeding sows high levels of fiber in gestation has been shown to result in increased feed intake in lactation (Hagen et al., 1987). Sows fed alfalfa haylage at 30, 60 and 90% of energy intake showed a linear increase in lactation feed intake. However, sows at the 60 and 90% intake levels had difficulty consuming enough energy to maintain body weight in gestation. Increasing gastric fill with high fiber diets prior to farrowing is practiced in commercial production units in an attempt to allow the sow to adjust to the large volume of feed to be consumed in lactation. The influence of protein level fed in gestation and lactation can be seen in lactation performance of sows. Studies conducted by Mahan and_Griffo, (1975) and O’Grady (1971 and 1975) demonstrate that low levels of protein fed in gestation will result in reduced consumption of a low protein lactation diet or an increased intake of a high protein lactation feed. Conversely, sows fed a high level 01 It It c] di fe 19 fe 19 GS 19 re PE 1&1 an: li< Si! Ca] ant Cau 13 of protein in gestation do not show the same response in lactation feed intake ‘to various jprotein levels in the lactation diet (Shields et al., 1985). Thus, there is a clear interaction between protein level in the gestation diet and protein level in the lactation diet and lactation feed intake (Mahan 1975; O’Grady 1971, 1975; Shields et al. 1985). Severe amino acid imbalance has been shown to alter feed intake levels (Harper et al., 1970; Li and Anderson, 1983). Numerous studies indicate that low levels of essential amino acids in swine diets reduce growth performance in young pigs and lactation performance in sows (ARC, 1981; O’Grady et al. 1985; Aherne and Kirkwood, 1987; NRC, 1988). Studies determining the amino acid requirements of lactating sows indicate that lactation performance is enhanced by proper amino acid balance in the lactation diet (Lewis and Speer, 1973, 1974, 1975; Haught and Speer, 1977; Leonard and Speer, 1983). The effects of feeding various levels of macro- and micro-nutrients on lactation feed intake have not been well documented. Mahan and Fetter (1982) showed that a significant increase in lactation feed intake occurred when calcium (Ca) and Phosphorous (P) levels were raised from 0.6 and 0.5% to 0.8 and 0.6% for Ca and P, respectively. However, elevation of Ca and P levels beyond that level caused a non-significant reduction in voluntary feed intake la 14 level. Vitamin and mineral deficiencies and excesses are likely to result in reduced feed intake (ARC, 1981). E 'I I | l 1' l I i Several studies have shown an increase in lactation feed intake as parity advances (Mahan 1977, 1979; O’Grady 1985; Britt, 1986). A goal of the production manager is to have the sows gain a reasonable amount of weight with each successive parity (Whittemore, 1987). However, these gains diminish with the advancement of parity (Galet, et al. 1987; Kirkwood, et al. 1988). In addition, percent of body fat declines with each successive parity thus changing sow composition and nutrient requirements slightly (Whittemore, 1985). O’Grady et al. (1985) observed increased lactation feed intake with advancing parity only up to parity six. Kleiber (1975) suggested the use of metabolic body size as a consistant means of assessing maintenance requirements in animals. This assumes that ‘basal tissue: metabolism is similar for species that vary in size. Thus, the measure for maintenance requirement uses body weight (BW) in kg raised to the 0.75 power multiplied by an energy requirement in kcal. Recent studies using this suggestion indicated that lactating sows have similar maintenance requirements to other species using 110 kcal*BW kg°-'5 (Verstegen, et. al. 1985, Noblet and Etienne, 1987). Therefore, as the body weight of the sows increases with each parity, the maintenance requirements also escalate (Brody, 1945). l5 AmhisntJamnatnmndnlatixeMidiu The association of exposure to cool or cold temperatures with feed intake level in young growing pigs has been shown. Large increases in calorie intake occurs when pigs are exposed to cold temperatures in an attempt to maintain homeothermy (Ingram and Legg 1974; Herpin et al., 1986). However, farrowing houses are generally supplementally heated in the cooler months for the comfort and health of the baby pig. Therefore, rarely is the ambient temperature below 16°C. Lynch (1977) showed a 12% decrease in feed intake as temperature changed from 21°C to 27°C. The decline was a more dramatic 25% as the temperature went from 16°C to 27°C. O’Grady (1985) indicates that with each 1°C increase in farrowing house temperature sows will decrease feed intake by 0.1 kg per day. Various management techniques are used to maintain feed intake in warm climates. One method shown to improve sow comfort and maintain feed intake level is drip cooling (Nichols et al., 1985; Murphy et al., 1987). Water is dripped on the neck and shoulder of the sow at a rate of 1-3 gallons per hour to provide a wet skin surface thus allowing evaporative cooling of the animal. Another method that has been shown to improve sow comfort is zone cooling. Cool air is brought to the sow, at her snout via an air duct or tube system. Feed intake in zone cooled sows was numerically improved over non-cooled sows (Merkel and Hazen, 1967) 16 An increase in relative humidity of 10% at 27°C had no effect on lactation feed intake (Lynch, 1977). However, environmental chambers that are required to do these types of studies are not widely available, and thus ample data to fully evaluate this variable have not been published. One would expect a combination of high temperature and humidity to be uncomfortable and detrimental to sow lactation performance. Season The interaction between ambient temperature and season seems apparent. Lactation feeding level in the sow declines in the warm months and is elevated in the cool and cold months of the year (O’Grady et al. 1985; Britt, 1986). The data from Lynch (1977) does indicate a substantial reduction in feed intake as temperature increases. O'Grady (1985) suggests a 0.1 kg per day reduction in feed intake for each 1°C increase in average farrowing house temperature. Few studies document seasonal effects in feed intake, thus other secondary factors such as day length or temperature fluctuation may influence amount of feed consumed. I'll . I '1] . 1! Measured milk yield in sows increases, as number of pigs nursed is elevated. Estimated milk yield for a sow nursing twelve pigs is double that of a sow nursing four (Elsley, 1971; ARC, 1981). There are increased energy demands placed on a sow as litter size, and thus milk yield, 17 are expanded. This increase in litter size and milk yield, results in an increase in feed intake in lactation (O’Grady et al., 1985). Level of feeding has been shown to influence milk yield in lactating sows (Verstegen et al., 1985; Noblet and Etienne, 1986). This work was done in multiparous sows and feeding levels were widely diverse. Feeding levels of 7.5 to 10 Mcal ME versus 14.2 Mcal ME per day yielded an 8 to 18% reduction in milk yield. Therefore, reducing feed intake in lactation by design or due to improper management systems will reduce milk yield and thus piglet growth and size at weaning (Verstegen et al., 1985; Noblet and Etienne, 1986). Reese, et al. (1982 ab), Nelsen, et al. (1985), and Brendamuhl, et al. (1987) all showed a minimal effect on weaning weight of piglets when their primiparous dams were restricted in feed intake during lactation. Several factors may' play a part in. explaining this situation. First, primiparous sows generally do not farrow and raise as many piglets as do multiparous sows (Galel et al., 1987; Kirkwood et a1, 1988). Therefore, as indicated previously, as suckling intensity increases so does milk yield. Thus, gilts would have lower suckling intensity and lower lactation requirements. Second, and perhaps more importantly, the percent body fat in gilts is somewhat higher (ZS-30%) than the percent body fat of sows (IO-15%), and therefore gilts may be able to mobilize more energy reserves to maintain milk yield in lactation (Whittemore, 18 1987). (Nonetheless, the detrimental effects. of reduced feeding in lactation are apparent with increased incidence of anestrous sows (Reese et al., 1982 ab; Brendemuhl et al., 1987), reduced litter size in second parity sows (Reese et al., 1982 b; Kirkwood et al., 1987), and reduced longevity in the herd (Gatel et al., 1987; Kirkwood et al., 1988). W The segment of the lactation period has an impact on daily feed intake in the sow. Feed intake during the first week of lactation is variable (English, 1970; Stahly et al., 1976). No adverse effects were observed when ab libitum feed intake was allowed postpartum (Stahly et al., 1976). Feed intake levels increase as lactation progresses for up to five weeks. After the fifth week of lactation, feed intake begins to decline (Stahly et al., 1976; O’Grady et al., 1985). Mahan (1977) found similar results as feed intake for day 15 to 28 was significantly greater than for the day 1 to 14 period. As lactation progresses, milk yield in the sow increases thus heightening metabolic demands of the sow with a concurrent rise in feed intake (ARC, 1981; O’Grady et al., 1985). In most studies of lactation feed intake, weekly totals of feed intake are used as a measure of consumptory behavior during lactation with 28 days being a common end point. However, in situations with longer lactation lengths (5 to 7 weeks), feed intake tends to peak during week four or five of lactation and then begins to 1: S: 8L 8c 11 pr. 19 decline (O’Grady, 1985). This would follow a similar pattern seen in milk output by the sow over the same period (Smith, 1959 ab, den Hartog, 1984). Genetics The genetic background of a sow can have a significant effect on lactation feed intake. Pond et al. (1981) observed a lactation feed intake difference between Landrace, Yorkshire, Chester White and Large White breeds. However, this study used data from breed groups with widely varying number of pigs nursed (6.2 Chester White to 8.5 Landrace) which could result in feed intake differences. O’Grady et al. (1985) showed a breed difference between Large White sired sows versus Landrace sired sows (4.65 kg/d vs. 4.5 kg/d) with similar levels of productivity. There would be expected differences between breeds, particularly where litter size and milking ability were highly diverse. Fowler et al., (1976) suggested that continued selection for leanness in pigs may result in selection of ‘pigs with smaller appetites. This theory is difficult to substantiate, but, if correct, it would be suspected that sows selected for extreme leanness may be genetically limited in appetite level. W Maintaining high health standards in the sow herd would provide the opportunity for maximum sow performance in lactation. Many diseases affecting sow performance are a 20 major concern in managing the lactating sow for maximum feed intake and milk output. The objective of this section is not to elucidate all possibilities for disease effects on lactating sows but to show an important relationship between disease and feed intake in the lactating sow. Symptoms of many diseases includes an increase in core body temperature as a means-of combating the infection (Elmore and Martin, 1986; Furniss, 1987; Tubbs, 1988). In periods of hot weather, body temperature of the pig also tends to rise (Dauncey and Ingram, 1986). As a result of this increased core temperature, feed intake will most likely decline (Baile et al., 1981; McCarthy et al., 1984; Blood and Radotits, 1989). The mastitis, metritis and agalactia (MMA) syndrome, which results in increased body temperature of sows, continues to be a problem for swine producers. Measuring the severity of an MMA problem using rectal temperature as an aid in identifying an affected sow has been described (Furniss, 1984; Elmore and Martin, 1986; Tubbs, 1988). A general problem with this syndrome is reduced feed intake. Thus, the health of the sow as it is related to her body temperature and behavior can have a great influence on lactation feed intake. With a. significant number of reports indicating that MMA is an industry problem, one might expect to see feed intake variation due to infection and other factors in the periparturient period (Whithair et al., 1983, 1986). 21 W Ideal management of a farrowing facility would require an observer to be present at all times. This possibility is not practical in most situations, and therefore sows are left largely unattended at parturition and throughout lactation. In most cases producers observe sows and litters only when feeding. Producers usually feed sows twice daily thus allowing observation of the sows at those times. More frequent feeding than twice daily during lactation may stimulate feed intake slightly (Hogberg, et al. 1983; Moser, 1984). E3£d_flaxnzs Improving feed palatability so that animals are enticed to consume more feed is the goal of using flavoring agents in feed. Feed flavors are commonly used in commercial swine production units, and producers apparently perceive them to have value in improving feed intake. However, published data do not support the notion of improved feed intake with the use of flavoring agents (Moser, 1984; Matzat et al., 1985). W: Various molds and mycotoxins can affect feed intake in pigs (Nelsen, 1979; Carson, 1986). Feed intake levels and therefore performance of pigs are reduced with effective levels of various mycotoxins such as aflatoxin, zearalenone and deoxynivalinol. Therefore, one would expect similar 22 results in lactating sows. In addition, long term storage of feed leads to inactivation of vitamins and rancidity of fats. Fresh feed manufactured from high quality ingredients not subjected to long term. storage would be ideal for maintaining peak feed intake levels. E I 'l E i'l The energy density of the lactation diet does affect feed intake during lactation. Adding fiber to the diet will dilute the energy content of the feed. If excess fiber is added to the diet of lactating sows, they will compensate by increasing feed intake (ARC, 1981; Zoiopoulos et al., 1982). However, with high producing sows being in a negative energy balance during lactation, any reduction in energy content of the diet only heightens lactation weight loss. Conversely, if energy concentration of the diet is increased by adding dietary lipids the results are not as clear» Several studies summarized by Pettigrew (1981) showed a slight reduction in feed intake but an overall increase in daily ME intake. However, others including O’Grady and Lynch (1978) showed a small increase in feed intake and thus a large increase in the overall energy intake when fat was added to the lactation ration. In growing pigs, addition of fat to the ration has resulted in a reduction in feed intake but an equal or superior rate of gain (Whittemore, 1987). Thus, it is speculated that in studies where an increase in lactation feed intake is observed the addition of fat to the diet may 23 improve the palatability of the diet and therefore stimulate appetite. E l' l' E I . | l . 1 I I' An attempt has been made to estimate lactation feed intake in sows using prediction equations. These equations have been developed using current available data. The NRC (1987) equations use daily digestible energy intake as the dependent variable in the regression equation. The independent variable listed is day of lactation. The formula used is: DE1 = 13,400 + 596 Day - 17.2 Day2 This formula was developed with few data that measured daily feed intake. In addition, factors such as litter size, sow backfat, and metabolic body size are not considered. Snmmarx In reviewing the various factors that can affect feed intake in lactating sows, it is apparent that an interaction of any or all of these factors can exist in a particular facility (Figure 1). Factors such as previous management, lactation environment, genetics, diet quality can all have an impact on lactation feed intake. Nonetheless, if management and genetics are optimal, sows will generally still be in a negative energy balance during lactation. This fact makes it imperative that management and husbandry Figure 1. Management ”an Hummumtmdyeue Plfltv Percent body tat Suckling intenslty “mufiud Stage oi lactation Ambient temperature Energy density of diet Feed quallty Sow body temperature Genetic improvement Nutrient imbalance 24 Change in item -> ++++~>++++++ Relationship of Various Environment, Genetic and Feeding Level in Lactating Sows. Etiect on lactation teed intake Health Factors Nutrition, with 25 techniques used during the lactation period be reviewed and improved in pig production facilities. If conditions such as excess body weight and fat gain in gestation are compounded with increased ambient temperatures, the combination will lead to large weight losses in lactation. Perhaps, excess body tissue losses will lead to a subsequent reduction in reproductive performance and reduced longevity in the herd. In addition, most of the factors reviewed have a negative effect on feed intake. Stimulation of feed intake in lactation is very difficult to accomplish particularly when utilizing only management techniques. Predicting lactation feed intake level can be accomplished. However, the accuracy with which one can accomplish this task is questionable. E I H'l B l . I I I. S The previous section reviewed the effects of environment, management, nutrition, genetics and health on daily feed intake in lactating sows. This portion of the review will deal with the metabolic and physiological changes caused by and as a result of varied feeding levels in lactating sows. The efficiency with which a lactating sow can convert feed and body tissue into milk is variable. As lactation progresses, the blood metabolite and circulating hormone profile in the sow will be altered. In addition, as lactation feeding level is varied ovarian function and thus reproductive performance can be affected. 26 W The lactating sow has energy requirements to maintain basic metabolic functions. In addition, energy is required for milk synthesis and secretion . Lactating sows generally lose weight as body tissues are catabolized to meet lactation energy requirements. With varied levels of feeding in lactation, sow weight loss, milk yield and milk composition can be altered. Determining the energy requirements of sows in lactation requires definition of maintenance and production needs. The measurement of energy input from the amount of diet consumed is defined by total or gross energy intake. Subtracted from this total or gross energy input is the urinary and fecal energy losses. Urinary energy loss must be corrected for nitrogen balance as this is a measure of body and dietary protein conversion to energy. Additional energy loss must include assessment of loss from methane production. In addition, the energy output from the sow in the form of milk must be measured. Furthermore, if the sow is in a negative energy balance, weight loss must be measured as catabolism of body tissue will yield energy for maintenance and milk synthesis. Heat production, as a by-product of metabolic function and enzyme activity, is the final measure of total energy need (Bowland, 1964 ab; 1967). In various early studies (Smith 1959 ab), a common measurement practice was to use total digestible nutrients 27 (TDN) of the feed consumed. This value was converted to metabolizable energy (ME) on the basis of 3991 kcal/kg TDN (Brody, 1945). Comparisons of gross efficiency of milk production were calculated by using the following formula: Gross energy of milk produced (kcal) Gross efficiency = ------------------------------------- ME of sow feed intake (Kcal) Work by Diggs et al. (1965) indicated a need to add a correction factor for nitrogen balance to factor in amino acid conversion to glucose. In addition, correction for nitrogen balance will measure catabolism of muscle protein resulting from a need for gluconeogenesis and maintenace of blood protein levels. Kleiber (1975) suggested energetics studies should be based on a standard metabolic body size. The standardized value is body weight in kg°-75 (NCR, 1981). The estimation of lactation efficiency now becomes: Gross energy of milk Gross efficiency = ----------------------------------------- Net energy from diet 1 Energy value of wt change - Maintenance requirement where gross energy of milk is total energy output of milk, net energy from the diet is the nitrogen corrected metabolizable energy, energy value from weight change is energy liberated by catabolism of body tissue, and maintenance requirement is calculated to be 110 kcal.BW (kg)°'75. Determination of each of these factors then 28 becomes important in the measurement of energetic efficiency. "'1! I I. Measurement of daily energy secreted by sows in milk form is important and difficult to accurately measure. The measurement of gross energy in milk is accomplished by using a composite sample of milk and subjecting it to the bomb calorimetry method (Kleiber, 1975). Milk sampling technique can affect milk composition. Use of manual stimulation versus stimulation of milk ejection with exogenous oxytocin will yield slightly different milk fat levels with oxytocin induced ejection being slightly lower. This will translate into slightly lower gross energy value for those milk samples collected with the aid of exogenous oxytocin (den Hartog et al., 1987). The estimation of total milk yield is another difficult parameter to measure. Several studies using various measurement techniques have attempted to estimate milk yield in lactating sows (Van Spaendonck and Vanschoubroek, 1964; den Hartog et al. 1984, 1987; Speer and Cope 1984; Verstegen et al., 1985; Noblet. and. Etienne, 1986). 180th isotope dilution technique as well as the weigh-suckle-weigh method have been used with the latter being most common (Rudolph, 1984). In addition, hand milking (den Hartog, 1987) and machine milking (Miller, 1981) have been used. The accuracy with which one can measure milk yield is variable. Weight 29 losses in piglets during the suckling period cause discrepancies in weight change attributed to milk intake. The weight loss due to urination, defecation, metabolism, evaporation, waste or spillage of milk cause inaccuracies in the measurement of milk yield (Klaver et al., 1981; den Hartog, 1984; Verstegen et al., 1985). Also, alterations in nursing schedule due to sow uncooperativeness during a measurement period will influence the accuracy with which yield estimates can be made. The measurement during an eight hour period of the day can be used to predict daily yield with reasonable accuracy (Mahan et al., 1971 Speer and Cox, 1984). The weigh-suckle-weigh method uses 60-72 minute intervals between nursing (Barber et al., 1955; Whittemore and Faser, 1974; Lewis et al., 1978; Speer and Cox 1984; Noblet and Etienne, 1986). Measurements have been taken at various periods during the day' and throughout lactation (Mahan et al., 1971; Delange et al., 1980; den Hartog, 1984, 1987; Speer and. Cox, 1984; Verstegen, 1985, Noblet and Etienne, 1986). The lactation curve of a sow generally peaks at week 3-4 of lactation (Verstegen et al., 1985; Noblet and Etienne, 1986; den Hartog et al., 1987; Whittemore, 1987). However, milk yield is highly variable between sows and between studies (Smith 1959 b; Mahan et al., 1971; Verstegen. et al., 1985; Noblet and Etienne, 1986). The range in milk yield has been reported to be 3 to 9.5 kg per day (O’Grady et al., 1973; Lewis et al., 1978; den Hartog, 1984). 30 The composition of milk has been shown to be quite variable. Several factors can affect milk composition and total energy secreted in the form of milk. Seerley et al. (1974) showed an increase in milk fat level by feeding fat in the diet 7 days prior to farrowing. Conforming evidence has been since published (Pettigrew, 1981; Moser, 1985). Adding fat to the lactation ration tends to increase milk fat levels (Boyd et al., 1982; Lellis and Speer, 1983; Moser, 1985, Seerley, 1985). Milk fat is also affected by limiting energy intake in lactation. Restricted energy levels reduced overall milk yield but caused an increase in fat concentration of milk. The total energy secreted as milk, when high and low levels of dietary energy were fed, were similar for both treatments (Verstegen et al., 1985; Noblet and Etienne, 1986; den Hartog et al., 1987). Fatty acid composition is altered in early lactation by reducing feed intake in sows. Oleic acid is produced in high proportion, as compared to other fatty acids, indicating sow adipose tissue break down (den Hartog et al. 1987). In general, total milk lipids decline slightly (8.0 to 6.8%) in a 28 day lactation (Brent, 1973; Hitchcock, 1973; Klaver et al., 1981; den Hartog, 1984; den Hartog, 1987). The percent lactose and protein remain somewhat constant throughout lactation at near 5% in whole milk (Brent, 1973; Jenness, 1985; den Hartog et al., 1987). Percent dry matter of whole milk remains stable or declines slightly through lactation (Brent et al., 1973; den Hartog et. al., 1987). Amount of 31 ash in whole milk tends to increase slightly as lactation progresses (den Hartog et. al., 1987). As the percent fat declines in lactation so follows the energy value (kcal/g) of milk. However, as lactation progresses milk yield peaks and total energy output is maximized. Energy output in the form of milk is approximately 8 Meal per sow per day (Klaver et al. 1981; Noblet and Etienne, 1986) or about 6.5 kg of total milk per day. NRC (1988) recommendations are 2 Meal of DE per kg of milk which corresponds to a 4.5 kg per day feed intake for sows producing 2.5 kg of milk daily. Milk yield, as it relates to energy output, can be stated on a daily milk energy (kcal) per BW kg°"’5. Pigs are relatively high on the energy output scale as compared to other species (Table 1). In addition to gross energy output of milk secreted, the energy costs for biosynthesis and secretion must be considered since these energy costs are beyond those of normal maintenance (Oddy et al., 1984; ‘Roberts and Coward, 1984; Collier, 1985; Prentice and Prentice, 1988). As energy demands due to onset of lactation increase, many changes and adaptations occur in most mammals. The blood flow and nutrient utilization is increased in mammary tissue. As a result of increased energy demands in lactation, feed intake is increased to compensate. In addition, the digestive tract increases in size and absorptive capacity. The increase in organ size may be due to the increased feeding level (Cripps and 32 Table 1. Daily Milk Energy Yield per Metabolic Body size.* Species Daily Milk Energy (kcal)/BW kg°-75 Mouse 320 Rat 230 Rabbit 180 Guinea pig 85 Dairy cow 335 Beef cow 60 Dairy goat 275 Pig 250 Sheep 120 Primate 25 Human 25 * Adapted from Prentice and Prentice (1988). 33 Williams, 1975; Koong et al., 1982). Liver size and small intestine ‘weight and length were increased in lactating sows. Furthermore, when litter size was increased from 8 to 12 pigs nursed, liver, small and large intestinal size was enlarged (Collier, 1985; Pelletier et. al, 1987). These adaptations have been noted in rats but not in humans (Jolicoeur et al., 1981; Prentice and Prentice, 1988). Also, there is i a general increase in lipolysis, gluconeogenesis and glycogenolysis with a concomitant decrease in lipogenesis. As lactation progresses, there is a general mobilization of protein reserves, an increased absorption and mobilization of minerals, as well as greater water intake with a resulting expansion in plasma volume (Collier, 1985). The uptake of nutrients by the mammary gland is greatly increased in lactation. As these nutrients move into the mammary epithelial cells and are converted to milk constituents, energy is required. Active synthesis of lactose, milk lipids and various milk proteins all require utilization of energy within the epithelial cell to form these substrates (Bauman and Currie, 1980; Collier, 1985; Prentice and Prentice, 1988). E i 'l l l E I] . 1 I I. Measuring maintenance requirements in lactating sows is an arduous task. Nutrient intake can be measured with a certain degree of accuracy. However, the assumption must be made that intake of sow lactation diet by the offspring 34 would not significantly affect total nutrient uptake measured for the sow. This is particularly true where piglet and sow are housed in a common stall. In addition, collection of urine and feces to determine absorption and retention of nutrients could be affected by common excreta from sow and offspring. Also, as previously mentioned, the measurement of milk energy secreted is not as precise as one would desire. The use of calorimeter chambers allows the measurement of oxygen utilization and carbon dioxide production (Verstegen et al., 1985; Noblet and Etienne, 1986). This measurement requires adjustments to be made for piglet metabolism, however. In addition, the measurement of maintenance requirements must include an accounting for body weight change. Maintenance requirements would be defined as the amount of nutrients required to neither gain nor lose body stores of nutrients. In the prior section, it was indicated that Klieber (1975) suggested the use of metabolic body size (BW kg°~75). Metabolism for a given cell mass would yield energy for cell function plus a heat increment due to inefficiencies in cellular activities. The recommended maintenance energy level for a lactating sow is 110 kcal/kg BW°~75 (Verstegen et al. 1985; Noblet and Etienne, 1986; NRC, 1988). This level of feeding would meet energy requirements for normal metabolic function and muscle activity' in El thermoneutral environment. With changing environmental conditions and activity levels, the maintenance requirements may be altered. 35 Feeding lactating sows to meet maintenance requirements and lactation requirements does not always equal energy intake. Level of feed intake, energy density and nutrient digestibility of the diet will 'all affect energy balance. If the energy balance is positive, weight gain in sows will occur (Whittemore 1980, 1987; King and ‘Williams, 1984). Conversely, if the energy balance is negative, the sow will begin to liberate body energy stores of both fat and protein (King and Williams, 1984; Brendemuhl et al., 1987; Whittemore, 1987). When considering the breakdown of body tissue to provide substrate from mammary tissue utilization, the efficiency and impact on other bodily functions must be taken into account (Moe et al., 1971). ‘The efficiency of converting dietary energy to stored body energy is approximately 80% (Moe et al., 1971; Burlaeu et al., 1983; Close et al., 1985; Noblet and Etienne, 1987). Noblet and Etienne (1987) estimated that the conversion of body tissue energy reserves to milk energy can be accomplished at a relative efficiency of 86-89%. Therefore, the overall efficiency of converting gestation energy to milk essential energy is approximately 68-71% (Verstegen et al., 1985; Noblet and Etienne, 1987). Comparing this to the efficiency of direct conversion of feed to milk energy is calculated to be slightly higher at about 70-74% (Verstegen et al., 1985; Noblet and Etienne, 1987). Therefore, it appears to be more efficient to convert dietary nutrients to milk energy dln lactation and limiting feed conversion to essential 36 energy stores in gestation. Furthermore, as previously stated, excess weight or fat gain in gestation will reduce nutrient intake and increase catabolism of body energy stores in lactation. However, ad libitum intake of nutrients in lactation does not eliminate weight loss. Therefore, a balance between proper energy stores in gestation and maximum feed intake in lactation must be maintained (Close and Cole, 1986; Kirkwood et. al. 1988). Accurate estimation of body fat changes in sows during gestation and lactation has been difficult. Using ultrasonic devices to measure backfat on live animals and regressed it with actual carcass measurements an R2 of 0.80 was obtained (Sather et al. 1978). However, when body weight and carcass backfat were used as regression coefficients the R2 ranged from 0.20 to 0.53 (Whittemore et al. 1980; King et al., 1986; Whittemore, 1987) indicating a wide range of body fatness at a given weight. The level of accuracy using these methods may not be what is needed or desired. However, the method is easy and noninvasive. From a practical perspecive, use of ultrasonic devices or visual evaluation of sow body condition can be useful methods of managing the gestation feeding level of sows. An alternate method to measure body fat, from a research perspective, is to consider the relation of body water to body fat using isotope dilution technique (Knudson et al., 1985). This method relies on the relationship between body water and body fat (R2 0.85). There are, however, changes in this 37 relationship as lactation progresses and body fat stores are liberated. (Rudolph, 1984; Whittemore, 1987). Weight loss, as it is associated with protein, fat and water balances in lactation can be misleading. As fat is catabolized from adipose tissue it is replaced by water thus increasing the water to protein ratio (3.5 to 4.0) in the body of the sow (Whittemore, 1987). This results in inaccurate assessments of fat loss in lactation and results in further weight loss at weaning (Whittemore, 1987). Included in the discussion of energy balance and maintenance requirements, evaluation of nitrogen balance must be considered. Loss of body weight in lactating sows is assumed to be mostly fat. The rate of weight loss commonly assumed is 80% fat 20% protein. However, as energy is restricted in the diet, the loss of urinary nitrogen increases and nitrogen balance becomes sharply negative (Brendemuhl et al., 1987; Noblet and Etienne, 1987). Nitrogen balance in lactating sows is affected by both dietary protein and energy levels. Negative nitrogen balance is experienced in both low energy and low protein intake situations. Amino acid catabolism increases as lactation progresses as a result of increased demands for glucose as a substrate for milk synthesis (Brendemuhl et al., 1987; Noblet and Etienne, 1987). Sows fed high protein diets had higher amino acid catabolism than those fed a low protein diet. This resulted in sows conserving body protein stores and increasing body fat catabolism (Brendemuhl et 38 al., 1987). Thus, nitrogen balance is variable in lactation, depending on dietary nitrogen levels and lactation nitrogen demands. If ample supply of amino acids are present, a negative nitrogen balance situation should not occur (Whittemore, 1987). Summer! Developing a strategy for maintaining maximum milk yield while keeping loss of body fat and protein stores to a minimum is essential for maximum sow production. Measurement of milk energy yield is not as accurate as it might be, however, the weigh-suckle-weigh method is widely used and from recent studies, such as Noblet and Etienne (1987) can yield. accurate information” The effects of varied energy and protein intake in lactation affects milk yield and composition. As dietary energy is decreased sow milk yield is decreased. Milk fat becomes more concentrated as sow energy intake is restricted, with equivalent daily milk energy output to sows fed normal feed intake levels. The efficiency of converting lactation feed energy to milk energy appears to be slightly more efficient than building excess energy stores in gestation and converting it to milk energy in lactation. Maintenance requirements for the lactating sow have been measured to be about 110 kcal/kg BW°°75. This requirement level can be affected by environment and activity level of the sow. Metabolic rates and therefore energy requirements will increase with a 39 decrease in ambient temperature. Nitrogen balance is affected by both protein level of the diet as well as energy level fed. As energy level fed is decreased, there is a concomitant increase in amino acid breakdown and therefore nitrogen excretion. In a low energy high protein situation, amino acids are broken down for glucose production. However, if adequate protein and energy are provided, nitrogen balance should remain near equilibrium. Nonetheless, for high producing sows, the opportunity for environmental and physiological factors to affect level of feed intake are great and thus the possibility for a sow to be in a negative energy and nitrogen balance is enhanced. El . l . 1 E l [E I. E I . I I This section of the review will look at those factors involved in controlling meal size and meal frequency. Various stimuli are used to mediate responses to different levels of food intake and nutrient density of the diet. I will not attempt to describe in detail all the physiological, hormonal and neural activities of the body as they relate to control of food intake. However, an attempt will be made to discuss these areas as they can explain changes or responses to feeding levels in lactating sows. After looking at the various physiological systems involved in. controlling feeding level, it is apparent that each system is intertwined with several others. A short 40 description of the function of each system will be attempted. E l |° I 1 E E I . ll Food preference due to taste preference and food refusal due to taste aversion have been methods used to stimulate or reduce appetite in animals (Houpt et al., 1979 ac). Smell of foOd apparently plays a very small role in feed intake levels. Olfactory bulbectomy had no effect on feeding level or pattern in pigs (Baldwin and Cooper, 1979). Change in osmotic pressure in the duodenum appears to yield responses in meal size. Solutions of NaCl and glucose yielded a response to increasing hypertonicity of each solution with decreasing feed intake (Houpt et al., 1979 a; Stephens, 1980). The duodenum, as compared to other locations in the GI tract, yielded a greater response to change in osmotic pressure on meal size. In addition, stimuli such as sight, smell, and taste of food, when combined, trigger a cephalic neural reflex which results in the release of large amounts of insulin and glucagon within the first minute of food. intake (DeJong et. al., 1977; Grossman, 1986). Several studies have shown that if food consumed is withdrawn from the esophagus or stomach via an esophageal or gastric fistula, marked increases in meal size and meal length will occur (Janowitz and Grossman, 1949; Young et al., 1974). As food is shunted out an esophageal cannula, meal length increases 'substantially, however, 41 feeding does stop indicating oropharyngeal metering of food. Food can be withdrawn from the stomach after feeding and the response is initiation of eating with the amount consumed equal to the amount withdrawn. This response is similar after a 40-50 minute delay (Snowdon, 1970). Stretch receptors in the stomacht appear» to send signals to 'the central nervous system via the vagus nerve when moderate to large amounts of food are ingested (Gonzalez and Deutsch, 1981; Geliebler et al., 1986). Nutrient content of the diet, protein, and simple sugars, appear to be monitored by the stomach, and this information is routed to the brain via the splanchnic nerve (Scharrer and Langhams, 1988). Stretch receptors in the duodenum appear to be active in limiting meal size also (Davis and Campbell, 1978). Various hormone and hormone like compounds are released by the gastrointestinal tract (Houpt, 1984). The first hormone is bombesin, which will reduce meal size when injected in mice and rats and appears to be involved in limiting meal size or provide meal ending stimulus. In addition, bombesin has been implicated in the release of cholecystokinin (CCK) (Morley, 1987; Scharrer and Langhans, 1988). Satiety may be mediated by the hormone CCK, which is released by the lining of the upper intestine. CCK decreases feeding and even causes post-feeding response and activity in rats (Antin et al., 1975). The activity of CCK can be lessened by various vagotomies performed on ascending 42 vagal afferents (Ewart and Wingale, 1983). Active immunization of animals against CCK will cause binding or tying up of the protein (Baile et al., 1986). As a result, feed intake has been shown to increase (9%) and weight gain was improved (17%) in rats (McLaughlin et al., 1985). Somatostatin is released by the pancreas and inhibits gastric secretions as well as GI tract motility thus decreasing nutrient absorption. It may act as a factor in limiting meal length. Somatotatin does inhibit feed intake in spontaneous feeding animals. However, it does not prevent eating in food deprived animals (Levine and Morley, 1982). Motilin is a peptide which has been shown to increase in the peripheral tissue during feeding. It has also been associated with increasing gastric contractions. Motilin has been shown to increase feed intake in food deprived but not satiated rats (Christofides et al., 1981; Garthwaite, 1984). E I l I. I J E E i 'l I In the digestive period where nutrients are absorbed, monitoring of nutrient levels takes place. Concurrent release of the peptides previously discussed occur. The mechanisms are not fully understood and must still be elucidated. As nutrients are broken down in the gastrointestinal tract and absorbed across the intestinal mucosa, they enter the portal vein. Hepatic activity is 43 important in monitoring various metabolic fuels. The liver is able to oxidize glucose, fatty acids and amino acids. In addition, glucose can be stored in the form of glycogen as a short term energy storage. Thus, since the liver is so vital in metabolic activities, it also appears to be vital with regard to food intake regulation. Russek (1981) proposed that hepatocytes, in contact with afferent nerve fibers, act as glucoreceptors. Thus, the membrane potential of the hepatocytes, as related to the current status of glucose and other substrate within the cell, would cause nerve cell resting or activation. Presumably upon activation of this nerve ending, along with other hepatocyte activations, a hunger response would be elicited. However, this is a fairly simple hypothesis and is not accounting for other factors such as quantity of fat stores, fat metabolism or energy balance (Freidman and Striker, 1976; Grossman, 1986). As eating begins, the stomach. and «duodenum secrete several hormones (CCK, somatostatin etc.) as previously mentioned. As absorption begins to occur, blood glucose levels begin to increase. Insulin is released as a cephalic response to initiation of food intake. However, as glucose levels increase during the meal a much larger release of insulin occurs (Stephens 1970; Grossman, 1986). This level of insulin peaks 45-60 minutes after the onset of feeding and declines rapidly therafter to baseline levels. Blood glucose levels follow a very similar pattern as seen in 44 insulin (Stephens, 1970; Grossman, 1986). As insulin levels are elevated, it facilitates conversion of glucose to glycogen in the liver as well as fatty acid formation thus promoting storage of nutrients. In addition, without insulin, glucose cannot enter most tissues with the exception of liver and brain. Furthermore, insulin facilitates transport of amino acids into cells. Pancreatic release of a combination of hormones along with insulin occurs on a continuing basis. Release of glucagon and somotostatin occurs, however, their release is low during the absorption and post absorption phase. Insulin continues to be released as glucose levels remain high (75-100 mg/dl in the rat; 65-95 mg/dl in the pig). However, as glucose levels begin to decline to baseline levels the release of insulin is reduced and the catabolic hormones, glucagon and somatostatin, are released in greater quantities. This release triggers the break down of glycogen to maintain blood glucose levels (Romsos et al., 1978; Grossman, 1986). Large doses of insulin intramuscularly cause a marked decrease in blood glucose levels (Stephens, 1969; Johnston, 1988). However, the onset of feeding is delayed for 30-60 minutes, even though blood glucose levels are below normal thresholds to initiate feeding (Stephens, 1969). Alternatively, if high levels of insulin are infused intravenously, the response is an immediate feeding activity» In (addition, a significant increase in the number of meals occurs (Stephens, 1969; 45 Grossman, 1986). Nonetheless, intravenous infusions of low levels of insulin resulted in reduced feeding levels in rats (Vander Weele, 1980). In addition to the hepatic monitoring of glucose levels, there also appears to be monitoring of glucose by the central nervous system (Scharrer and Longhens, 1988). Injection of glucose analogues, 2-deoxy glucose or 5- thioglucose, systemically or intracerebroventricularly, cause a reduction in glucose uptake by the brain cells and thus elicit a response of increased feeding (Miselis and Epstein, 1975; Stamoutsos et al., 1979; Slusser and Ritter, 1980). Therefore, these researchers concluded, monitoring of glucose levels must be occurring in the hypothalmus. Insulin is not required by the brain for glucose absorption and utilization. Insulin does not readily cross the blood brain barrier (Grossman, 1986). However, two portions of the hypothalamus do have specific receptors for insulin. These sections are the ventromedial hypothalamus (VMH) and the lateral hypothalamic area (LHA). These areas are active in the control of feed intake. A theory currently being considered involves the regulation of insulin sensitive glucoreceptors. When feeding occurs, insulin receptors are down-regulated to reduce the affinity of binding insulin and thus sensitize the glucoreceptors to lower glucose levels in the tissues. This is thought to cause neurally induced lipolysis. Conversely, if insulin receptors are up-regulated, the glucorecptors would be less 46 sensitive to glucose levels and give rise to lipogenesis (Le Magnen, 1981; Grossman, 1986). There is some evidence that long term regulation of body weight and thus feed intake level depends on concentration of insulin in cerebrospinal fluid (Woods and Porte, 1978). Lesions of the VMH causes hyperphagia and weight gain, whereas lesions of the LHA cause a general aphagia and decline in body weight (Stephens and Strubbe, 1987). In addition, lesions of various afferent axons to the brain cause attenuated responses to gastrointestinal and pancreatic hormones (Morely, 1987). There are a number of peptides and opioid stimulators and suppressors of appetite. Many are naturally occurring in the brain and are released at time of feeding (Morley et al., 1985; Baile et al., 1986). Several synthetic compounds have been used to enhance or suppress feeding level. These will not be discussed but their importance and effects are recognized (Mdrley et al., 1985; Baile et al., 1986). Psychological state has been implicated in changes in the level of feeding particularly in humans (Geliebter, 1979; Schanner and Longhans, 1988). Stress has an influence on eating habits in humans as well as other species. However, stress can result in both an increase in feeding level and a resultant increase in body weight or a decrease in feeding and a loss of body weight (Leune and Morley, 1983). The interrelationships between stress, peptides and brain opioids and feeding level are not well understood. However, the effects of various environmental stressors on 47 feed intake have been observed in sows in lactation (O’Grady et al., 1985; Britt, 1986). W I I ]'| I . 1' In the intermeal period, insulin levels decline while glucogen levels increase to maintain circulating glucose levels (Morley, 1987). During long term negative energy balance the baseline glucose levels tend to decrease through a lactation period (Ruiz et al., 1971). This decrease is a result of increased mammary tissue requirements for substrate in the production and synthesis of milk, as lactation progresses (Spincer et al., 1969). However, if suckling intensity and therefore milk yield are relatively low, a positive energy balance would be present. In this situation, glucose levels would remain stable through the lactation period, and therefore the decline in serum glucose levels as measured throughout lactation would not be observed. As lactation progresses, the demands of the mammary system to use available substrate increases. In high producing sows the demands are not matched by nutrient intake thus creating a negative energy balance. With the increase of glucagon and somatostatin in relation to insulin, the catabolism of body stores of glycogen, adipose tissue and protein is initiated. As feeding levels are restricted, non-esterified fatty acids (NEFA) and blood urea nitrogen (BUN) levels rise. This increase is observed, as 48 lactation progresses (Bauman and Currie, 1980; Armstrong et al., 1986). NEFA levels are elevated as a result of an increase in lipoprotein lipase activity resulting in triacyl breakdown to NEFA and glycerol constituents (den Hartog et al., 1987). The break down of adipose tissue allows the use of NEFA for maintenance energy and for some mammary gland incorporation directly into milk secretions (Linzell et al., 1969, Spincer et al., 1969). BUN levels are increased as a result of an increase in gluconeogenesis activity. Break down of amino acids to move into glucose forming pathways results in an increase in blood urea levels and generally a negative nitrogen balance (Armstrong et al., 1986; Noblet and Etienne, 1986). Insulin levels tend to decrease during lactation as a result of increased body tissue catabolism and mammary tissue use of substrate. Administration of insulin depresses milk yield as a result of non-preferential tissue nutrient uptake. As mammary tissue preferentially receives substrate for milk synthesis (Kronfeld et al., 1963), in a normal lactation situation, an increase in baseline insulin would be viewed as undesirable. However, after weaning, insulin levels are increased with a concurrent decrease in glucose, NEFA and BUN (Armstrong et al., 1986). E l' . E I Jil'l Feeding an, animal more than. ad libitum consumption levels should logically result in greater nutrient 49 availability, assuming digestion and absortion capacity are not limiting. Excess nutrients beyond. maintenance requirements are used for production purposes, whether it be growth or milk production. If feed intake surpasses production requirements via a feeding center stimuli or artificial methods of feeding, the excess nutrients must be utilized in some fashion. Pekas, (1983, 1985) developed a method for direct gastric feeding. This method was used to feed growing pigs in excess of ad libitum. As feed intake was increased by 20% over ad libitum fed counterparts, a resultant 40% increase in daily gain was observed. Pekas concluded that digestion and absorption were not limiting in reaching maximum growth rates, but rather feed intake limitations were suppressing growth performance. Blood metabolite levels for superalimentated (SA) animals were similar to those observed in a full feeding situation. Rate of protein and fat accretion were at a slightly higher level in SA pigs versus ad libitum fed controls, but the amount of feed needed for gain and composition of gain were similar in both groups. Although not measured, one might expect insulin to be increased for a longer period of time past feeding as feed and stomach fill levels are increased (Levine and Morley, 1983; Morley, 1987). As lactational demands on a sow are reduced, the possibility for positive energy balance increases. Thus, as seen in sows with small litter size or low milk yield, net weight and backfat gain is observed in lactation (Whitemore, 50 1987). If, however, a sow is in a negative energy situation even at ad libitum feeding levels, it is not clear if introducing additional nutrients will result in body weight and fat gain, or if milk energy output will be increased. When insulin is infused, milk yield is depressed due to general tissue uptake of nutrient and reducing preferential uptake by mammary tissue (Goldobin, 1976). Therefore, one might assume when a sow, in negative energy balance, is allowed an increase in available nutrient by means of feeding in excess of ad libitum, she would respond by increasing milk energy yield. E I. 1 1 EE I . E I' As previously discussed, restriction of nutrient intake in lactation results in a greater proportion of sows with atypical ovarian function (de Hartog and Vandersteen, 1981; Reese et al., 1982 ab 1984; King and Williams, 1984 ab; King, 1987; Johnston, 1988) and reduced reproductive performance (Hughes et al., 1984; Kirkwood et al., 1987). Anestrus, as a result of restricted feeding in lactation, has been most widely noted in primiparous sows (Reese et al., 1982 ab; King, 1987). However, restricted nutrients in multiparous sows appears to affect subsequent embryo survivability and therefore reproductive performance (Hughes et al., 1984; Kirkwood et al., 1987 ab). The lactating sow requires energy for maintenance, milk production and also for ‘tissue growth and repair as a result of the past 51 pregnancy. In addition, there is a certain level of energy required for normal ovarian function to occur. This level of energy appears to be related to feeding level in lactation and body reserves at lactation end. A 50% energy restriction in beef cattle during gestation and lactation resulted in a 75% reduction in number pregnant (Wiltbank et al., 1964). Also, energy balance the first 20 days in lactation was inversely related to number of days postpartum to display estrus. In sows, restriction of both energy and protein result in an increase in weaning to estrus interval (Reese et al., 1982 ab; King and Williams, 1984; King and Dunkin, 1986; Brendemuhl et al., 1987). Thus, increasing protein intake (O’Grady and Hanrahan, 1975; Brendemuhl et al., 1987) and energy intake (Reese et a1, 1982 b; Armstrong et al., 1986) resulted in a decrease in number of days from weaning to estrus as should be expected. Armstrong et al. (1986) and Johnston (1988) indicate sows that have been restricted in feed intake in lactation but display estrus immediately post weaning exhibit higher NEFA levels as compared to restricted sows that are anestrous. Partitioning of nutrients by the sow in lactation takes place with maintenance requirements and milk synthesis being highest priority. Ovarian function and related activity appears to be expendable. Therefore, when nutrients are limited and body stores of energy and protein are catabolized, a cessation of ovarian activity occurs. Nonetheless, this level may be different from animal to 52 animal and specific guidelines do not apply to each individual. Snmmau Physiological and psychological factors affect feeding level in all species. The influence of taste, smell and physical characteristics of the diet may result in variations in feeding level. Gastrointestinal tract hormones that are released when food is ingested affect meal size, meal length and feeding frequency. Hepatic and CNS monitoring of blood metabolites such as glucose, free fatty acids and circulating proteins indicate that these metabolites interact to modulate feeding activity. Pancreatic secretions of insulin, glucogon and somatostatin influence blood metabolite levels and thus, feeding interval. The interaction between systems is complex and integrated. In addition, the control of meal size and meal frequency is not well understood. The influence of environmental factors interacting ‘with. the 'metabolic and central nervous systems an greatly impact feeding levels in lactating sows. Blood borne metabolites and insulin levels vary during lactation. Glucose, free fatty acid, blood urea, nitrogen an insulin levels are affected to a greater extent as feeding level is restricted. Furthermore, as feeding level in lactation is restricted, ovarian function and activity are impaired, and reproductive performance is reduced. 53 conclusions Various environmental and nutritional interactions exist, in regard to feed intake levels of lactating sows. The influence of many factors such as litter size, parity, level of body fat, and temperature will influence level of feeding in lactation. However, the quantitative impact each of these has on daily feed intake has not been well defined. Each factor that was discussed in the initial section of this review has been researched. However, most studies on sow lactation feed intake use weekly or entire lactation feed totals to measure treatment effect. No data are available to evaluate effects of various factors on daily feed intake in lactating sows. In addition to environmental effects on feed intake, the physiological impact of feeding level must be considered. Level of stress as it relates to health or environment will influence the amount of feed consumed. The various blood borne metabolites such as glucose, free fatty acids and proteins influence feeding level. As energy and protein balances change in lactation, variations can be observed in blood metabolite levels, body composition and ovarian activity of the sow. Feeding growing pigs in excess of normal feed intake levels has been accomplished. These pigs increase body growth rate beyond that of littermates fed ad libitum. Therefore, a major factor that limits growth performance 54 growing pigs is the limitation of feed intake capacity. Sows that are in a positive energy balance gain body weight. Thus, if excess nutrients are introduced artificially into a high producing sow in a negative energy balance, will she be able to digest and absorb these nutrients, and how will these nutrients be partitioned to meet metabolic need? EXPERIMENT I Factors Affecting Daily Feed Intake in Lactating Sows .Intznductinn Feed consumption of sows during the lactation phase is highly variable. Many factors have been associated with affecting daily feed intake level in lactating sows (O’Grady et al., 1985; NRC, 1987). Predicting daily feed intake in lactating sows has been difficult due to lack of studies which measured feed intake on a daily basis. Stahly (1976) measured daily feed intake in lactating sows for eight days post partum. Several studies use weekly feed intake totals and then convert total or weekly values to mean daily feed intake (NRC, 1987). There are limited data to determine that influence of various environmental factors on lactating sow feed intake. NRC (1987) used the following prediction equation: DE1 = 13,400 + 596 days - 17.2 Dayz, Where the dependent variable, DE1, is digestible energy (Kcal) intake and Day is the day of lactation. However, it is apparent that environmental and management factors should be included in such an equation to more accurately predict daily feed intake in lactating sows. Studies have been conducted to determine effects of individual variables on lactating sow feed intake. Lynch (1977) showed a significant temperature influence on sow feeding level. Nichols et al., (1983) showed a significant increase in feeding level using a drip cooling system for 55 56 lactating sows. Environmental factors can affect sow performance in lactation which are directly related to feed intake and sow comfort in warm temperatures (Johnston et al., 1987). Britt (1986) «described seasonal effects on lactating sow feed intake. His report showed a substantial reduction in average daily feed intake during the hot months of the year, thus leading to the supposition that ambient temperature is the primary factor involved in limiting feed intake. As sows advance in parity, body size usually increased (ARC, 1981; Whittemore, 1987). Kleiber (1975) showed that as metabolic body size increases the maintenance requirements also advance. Mahan (1979) and Britt (1986) both indicated that feed intake in lactating sows increases with advancing parity. The milking ability or capacity of the sow will influence her lactation energy needs. Feed intake level in lactation can influence sow milk yield and thereby piglet growth rate (Verstegen et al., 1985, Noblet and Etienne, 1986). Therefore, sows with large litter size and above average milking ability may not reach maximum milk yield if environmental factors limit sow feed intake (O’Grady et al., 1985; Whittemore, 1987). Earlier work has shown effects of previous management and feeding sequences on lactating sow feed intake (Lodge, 1972; Mahan and Mangen, 1975; Brooks and Smith, 1980; O’Grady et al., 1985; Kirkwood et al., 1987ab). This is 57 especially noted when sows come into the farrowing house with excess body fat. As percent body fat in sows increase, lactation. feed intake is reduced (Salmon, Legagneur and Rerat, 1962; O’Grady 1985; Whittemore, 1987). The influence of lactating sow health status on feed intake is usually assumed to be significant (Baile et al., 1981; McCarthy et al., 1984). However, direct measurement of the relationship of sow body temperature on feed intake in lactation has not been documented. The MMA (mastitis, metritis and agalactia) syndrome has been implicated as a major cause of lactation failure. In many cases these sows have elevated body temperature and self restricted feed intake (Elmore and Martin, 1986; Tubbs, 1988). The effects of reduced feed intake in lactating sows have been discussed in detail in the Review of Literature. The understanding of various factors influence on feed intake in lactating sows may help maintain and improve sow longevity and productivity. The objectives of this study were: 1) to determine the relationship of various environmental and managerial factors on daily feed intake by lactating sows, 2) to determine the association between feed intake of lactating sows and performance of sows, and litter performance. W W. Data were collected on two hundred seventeen lactation periods during 20 month period. 58 The trial was conducted from January 1987 through October 1988 thus including all seasons. Sows were either purebred Yorkshire or Yorkshire x Landrace crossbred. A total of 147 sows were used in the study. Sows were housed in a common gestation facility until approximately d108 of gestation. Sows were then moved into a mechanically ventilated, environmentally controlled farrowing facility. In this facility sows were housed in farrowing crates .56m x 2.13m with space measuring .46m x 2.13m on either side of the farrowing crate to allow piglets to move away from the center area where the sow was located. Supplemental heat in the form of a heat lamp was provided for the piglets at farrowing through 2 weeks of age. Litter size was standardized to a range of 8 to 12 piglets within 24 hours postpartum. Sows were fed 2.2 kg/day of the standard gestation diet until parturition (Table 2). Sows were changed to the standard lactation diet (Table 2) and allowed ad libitum access to feed at d1 postpartum. Sows were fed twice daily at 0800b and 1500b. Orts were recorded at the end of each 24 h period. Feed was available to the sows at all times but excess feed accumulation was avoided. Sows were weighed and scanned ultrasonicallyl for backfat at the last rib 5cm right of the mid-line within 24 h of parturition. Sows were weighed and scanned ultrasonically at 7, 14, 21 and 28d postpartum or at weaning if lactation 1 Leanmeter, Renco, Inc., Mason City, IA. 59 Table 2. Composition and Calculated Analysis of Diets. % of Diet Ingredient Gestation Lactation Corn 70.45 73.80 Soybean Meal 14.50 22.00 Wheat Bran 10.00 Mono-dicalcium Phosphate 2.00 1.55 Calcium Carbonate 1.30 1.10 Salt .50 .50 Vit.-Trace Mineral Premix'L .60 .50 Vit.E-Selenium Premixb .50 .50 CTL-50c .05 Choline Chloride, 50% .15 TOTAL 100.00 100.00 Calculated_Analxais Metabolizable Energy (ME), Kcal/Kg 2996 3232 Crude Protein % 14.00 16.00 Lysine .64 .82 Calcium .92 .76 Phosphorous .80 .64 ‘ Composition was: Vitamin A, 132,276 IU; Menadione, 3.53g; D-Pantothenic Vitamin B12, 3.96mg; 2.0g; Fe, 12.0g/kg Premix. Zn, 5 Composition was Vitamin E, Premix. .66g; acid, 7.5g; Mn, 3310 IU; 661,380 IU; Vitamin D3, Riboflavin, .66g; Niacin, 2,64g; Choline, 88.18g; 7.5g; I, .11g; Cu, Selenium 19.8 mg/kg ° Provided 110.25 g chlorotetracycline per kg premix. 60 length was less than 28 days. Sow rectal temperature2 was measured once daily at 0800b and recorded. Daily high and low ambient temperatures3 were observed at 0800b on the recording thermometer and recorded. Litters were weighed at birth and at 7, 14, 21 and 28d postpartum or at weaning if lactation length was less than 28d. Piglets. were not allowed access to creep feed. Piglets had limited access to the sow lactation diet. Parity of sows in this study was 1 to 8. At weaning, sows were moved to a common gestation facility in individual stalls. Sows were fed 2.2 kg of the gestation diet (Table 2) daily. A mature boar was used twice daily to detect sows in estrus. Sows were judged to be in estrus if the sow allowed the boar to mount. Days from weaning to estrus were recorded. Statistical_Analxfiis. Data were subjected to correlation analysis (SAS, 1982). To. determine factors that cause variation in daily feed intake, regression analyses (first and second order) were used (SAS, 1982). The dependent variable was daily feed intake of sows from d1 to d28 in lactation. Independent variables included were: day of lactation, daily rectal temperature, daily' hight and low ambient temperature, litter size, parity, sow fat depth at farrowing, sow weight, sow weight change, season, breed and days from weaning to estrus. Backward elimination 3 Agricultural Electronics, Montclair, CA. 3 Lab Systems, Inc., Berkley, CA. 61 procedures were used (Gill, 1978) to determine those variables that explained a significant portion of the variation in daily feed intake. Multivariate analysis of variance was performed on components of the polynomial regressions (SAS, 1982). No differences in determining significant relationships were detected using this analysis, therefore, this analysis will not be discussed. Sow and litter performance were used to catagorize sow groups. Sow groups were compared using the General Linear Models procedure (SAS, 1982) for covariate analysis of variance to determine significant relationships between selected variables. Analysis of variance procedures were used to test mean differences for sow groups (SAS, 1982). These sow groups included various levels of daily, weekly and total lactation feed intake, sow backfat and weight change and litter weight change. Repeated measure in time was used in a split plot design with day of lactation being the period of time. Mean comparisons were accomplished using a priori Bonferroni t statistic. In all statistical analyses the sow was considered the experimental unit. All means are reported as least-square means. .Results Although none of the variables were highly correlated with daily feed intake of lactating sows, several tendencies can be seen (Table 3). Day of lactation was the variable most highly correlated with daily feed intake (r = .41). 62 Table 3. Correlation of Daily Lactation Feed Intake and Various Environmental Factors. Variable Correlation Coefficients‘ Day of lactation .41 Mean Daily High Temperature -.28 Mean Daily Low Temperature -.28 Sow Backfat at Farrowing -.17 Sow Parity .10 Season of the Year -.12 Number of Pigs Weaned .24 Feed Intake d1 of Lactation .18 ‘ Significant at P (.001. 63 Daily high and low ambient temperatures were correlated negatively with daily feed intake (r = -.28). This agrees with previous studies (Lynch, 1977) indicating a highly negative response in feed intake to elevated farrowing house temperatures. Backfat at farrowing was also correlated negatively with daily feed intake in lactating sows (P = -.17). This agrees with previous work indicating sows with greater body fat stores tend to consume less feed in lactation when compared to properly conditioned sows (Lodge, 1972; O’Grady et al., 1985). Sow parity was not highly correlated with daily feed intake, however, the correlation was positive (P = .10). Season of the year was correlated negatively with daily feed intake in lactating sows (P = - .12). The association between season, ambient temperature and lactation feed intake is similar to that reported by Britt (1986). The correlation between season and daily feed intake shows the negative effect of warm temperatures on feed intake level (P = -.12). Number of pigs weaned was correlated positively with daily feed intake level in lactating sows. Thus, as number of pigs weaned increased feed intake level increased (P = .24). Feed intake on d1 of lactation was also correlated positively with daily feed intake throughout lactation (P = .18). Thus, sows that consumed large amounts of feed on d1 of lactation tended to consume large amounts of feed throughout lactation. A second order regression analysis was used to estimate daily feed intake using day of lactation as the sole 64 variable, this accounted for 21% of the variation in daily feed intake of lactating sows. The equation was as follows: Y = 2.94 (1.69) + 0.29 (1.011) x1 - 0.0068 (1.0004) an2 n = 217 R2 = .22 Where Y = daily feed intake of lactating sows (kg), x1 = day of lactation. The number of observations was 217 sows with 28 daily feed intake observations recorded. Although a relatively small amount of the variation was explained using this equation it was a highly significant portion (P<.001). Second order regression analysis was used to determine the response of sow feed intake to factors measured daily. The equation is as follows: Y = 8.36 (1.22) + 0.294 (1.01) x1 — 0.006 (1.0003) x12 - 0.079 (1.011) x2 - 0.16 (1.016) x3 n = 217 R2 = .31 Where Y = daily feed intake of lactating sows (kg), x1 = day of lactation, x2 = daily high ambient temperature, x3 = daily low ambient temperatures. This equation accounted for a highly significant portion of the variability in feed intake (P<.001). However, only 31% of the variation in daily feed intake of lactation sows could be explained using this equation. Feed intake was calculated on a weekly basis and regressed with those variables measured on a weekly basis. 65 These variables were sow weight, sow backfat depth, litter weight and week of lactation. The model would therefore be: Y = 24.1 (12.65) + 0.062 (1.011) x1 - 0.60 (1.09) x2 + 0.289 (1.040) x3 + .53 (1.06) X4 n = 217 R2 = .33 where Y = weekly feed intake total (kg), x1 = sow weight (kg), x2 = sow fat depth (mm), x: = litter weight (kg), x4 = week of lactation. The equation accounted for 33% of the variation in weekly feed intake. This was, however, a highly significant portion of the variation in daily feed intake (P<.001). Regression analysis was accomplished using those variables available to a producer at the beginning of lactation. An all inclusive list is not possible, however, those variable measured were used in the analysis. The equation is as follows: Y = 1.39 (1.25) + 0.30 (1.01) x1 - 0.007 (1.0003) x12 + .233 (1.014) x2 - 0.08 (1.006) x3 + 0.002 (1.0005) x4 + 0.074 (1.017) x5 - 0.199 (1.023) x6 217 n R2 = .38 Where Y = daily feed intake of lactating sows (kg), x1 = day of lactation, x2 = number of pigs nursed, x3 = sow last rib fat depth at farrowing (mm), x4 = sow weight at farrowing (kg), x5 = parity of sow, xe = season at the year. A highly 66 significant portion of the variation in daily feed intake was explained using this equation (P<.001). However, only 38% of the variation in daily feed intake could be explained using this analysis. The regression analysis using variables measured prior to end during lactation explained the largest proportion of the variation in daily feed intake. The model is: Y = 4.55 (1.27) + 0.30 (1.009) x1 - 0.007 (1 .0003) x12 - 0.06 (1.01) x2 - 0.11 (1.015) xa - 0.033 (1.005) x4 + 03089 (1.012) x5 + 0.135 (1.022) xe - 0.047 (1.002) x1 + 0.045 (1.002) x3 + 0.033 (1.017) x9 + 0.114 (1.015) x10 Where Y = daily feed intake (kg), x1 = day of lactation, x2 = daily high ambient temperature (°C), x3 = daily low ambient temperature, x4 = sow last rib fat depth at farrowing (mm), x5 = sow parity, xs = season of the year, x1 = sow weight change in lactation (kg), xa = 21d litter weight (kg), xe = number of piglets nursed, x10 = feed intake on d1 lactation. This equation explained a very significant portion of the variation in feed intake (P<.001). This equation also explained 44% of the variation in daily feed intake of lactating sows. Mean feed intake as measured on a daily basis is reported in Table 4. Mean daily feed intake for the entire trial is 5.36 kg. The overall pattern of feed intake through lactation using 217 observations is shown in Figure 2. Sows were separated into groups based on sow and litter performance levels reported in previous work or where 67 Table 4. Mean Lactation Feed Intake. Day Feed Intake, kg X SEM 1 1.86 5.36 .19 2 3.36 3 4.04 4 4.22 5 4.63 6 4.85 7 4.99 8 5.13 9 5.23 10 5.49 11 5.53 12 5.71 13 5.67 14 5.53 15 5.67 16 5.81 17 5.82 18 5.71 19 5.90 20 5.94 21 6.08 22 5.98 23 6.03 24 5.99 25 6.07 26 6.16 27 6.19 28 6.24 68 a? u! 8 E E II- —.— m 1 L J L l l l l l 1 4 7 10 13 16 19 22 25 28 DAY OF LACTATION Figure 2. Mean Daily Feed Intake of Sows in 28d Lactation. 69 natural separation occurred in distribution of sow and litter performance. The relationship between feed intake of lactating sows and ambient temperature was evaluated. Feed intake level was evaluated on the basis of mean daily high temperature in lactation to which sows were exposed (Table 5). The three temperature exposure levels were (22°C, 22-26°C and >26°C. Significant reductions in feed intake of lactating sows were seen, as ambient temperature was increased (P<.01). Sows exposed to >26°C farrowing house temperature tended to have a reduced feed consumption pattern (P<.14), especially the first week of lactation, as compared to the remaining two sow groups (Figure 3). The relationship between ambient temperature and feed intake of lactating sows was further evaluated using mean daily low ambient temperature (Table 6). Data analysis was accomplished using sow groups exposed to (21°C, 21-24°C or >24°C. As temperatures to which sows in lactation were exposed increased, a significant reduction in feed intake was observed (P<.01). Sows exposed to cooler temperatures in lactation reached higher levels of feed intake more rapidly (P<.01) the first week of lactation (Figure 4). Sows exposed to hot daily high temperatures (>27°C) in lactation were further evaluated on the basis of mean daily low temperature. Sows with exposure to temperatures >27°C were exposed to mean daily low temperatures (24°C or 224°C 70 Table 5. Relationship of Mean Daily' High Temperature in Lactation with Mean Daily Feed Intake in Lactating Sows. Item n 61 56 100 SEM Daily High Ambient Temperature, °C <22 22-26 126 Mean Daily Lactation Feed Intake, kg 5.9‘ 5.6b 4.8c .17 '- b. c Means with different superscripts differ (p<.01). GROUP Pd! A {I boo-1r 1r?” a 8 HI I E 4 3 m a II- ”. e80 2 "Q" "c -0- e'c ‘ l l J l A J l 1 4 7 10 13 1O 19 22 25 28 DAY OF LACTATION Figure 3. Relationship of Daily High Ambient Temperature and Daily Feed Intake in Lactating Sows. 71 Table 6. Relationship of Mean Daily Low Temperature in Lactation with Mean Daily Feed Intake in Lactating Sows. Item n 54 102 61 SEM Daily Low Ambient Temperature, °C <21 21-24 >24 Mean Daily Lactation Feed Intake, kg 6.0II 5.2b 4.6c .15 a. 5- ° Means with different superscripts differ (p<.01). GROUP Pofl1 GROW 2 “IE Pa.” .3 g D 3 IL I) fi —0— are 1;! “'0’“ WC "9"' are 0 l l l l A j l l 1 4 7 10 13 1O 19 22 ‘ 25 28 . OAYWLACTATDN Figure 4. Relationship of Daily Low Ambient Temperature and Daily Feed Intake in Lactating Sows. 72 (Table 7). Sows that were exposed to the cooler (<24°C) daily low temperature consumed significantly more feed (P<.04) than those sows that remained in warm temperatures (124°C) (Figure 5). The relationship of season of the year with feed intake of lactating sows was evaluated (Table 8). When feed intake in the cool seasons of the year, fall, winter, and spring, were compared no significant differences were seen (P>.10). However, in the summer or hot months of the year feed intake was significantly reduced (P<.001) compared to the remaining seasons of the year (Figure 6). Further analysis was done using ambient temperature as a covariate. Temperature was a significant covariate (P<.01). Nonetheless, after covariate analysis of variance season remained a significant effect (P<.02). The influence of back fat depth (BF) at farrowing on daily feed intake of lactating sows was evaluated (Table 9). Daily feed intakes of sows with <13, 13-15, 16-18, 19-21 and >21 mm of BF measured at the last rib within 24 h of farrowing was compared. Sows with <13 m of BF consumed significantly more feed than sows in each of the other fat depth categories (P<.05). Sows in the 13-15 and 16-18 mm of BF categories consumed similar amounts. of feed (P>.10). Mean daily feed consumption by sows with 19-21 mm BF and >21 mm BF did not differ (P>.10). However, sows in the 13-18 mm BF range consumed (P<.05) more feed than sows with >19 mm BF (Figure 7). Sow weight at farrowing was used as a covariate 73 Table 7. Relationship of Sows Exposed to Hot Daily High Temperature (>27°C) and either Warm (>24°C) or Cool (<24°C) Daily Low Temperature with Mean Daily Feed Intake of Lactating Sows. Item n 25 31 Mean Low Ambient Temperature >24°C (24°C Mean Lactation Feed Intake 4.4‘ 5.3b 4: 5 Means with different superscripts differ (p<.04)- am 'C-u 0‘..‘ 0‘. .‘ caour a nu: mm {.0 .' " FEEDIMTAKELkg l A l i 4 7 to 1: to to 22 as ea nav¢u=Lacwarlxi Figure 5. Relationship of Sows Exposed to Hot Daily High Temperature (>27°C) and either Warm (>24°C) or Cool (<24°C) Daily Low Temperature with Mean Daily Feed Intake of Lactating Sows. 74 Table 8. Relationship of Season of the Year with Mean Daily Feed Intake of Lactating Sows. Item n 39 70 71 37 SEM Season Dec-Feb Mar-May Jun-Aug Sep-Nov Mean Lactation ' Feed Intake, kg 5.85 5.65 4.65 5.55 .15 5- 5 Means with different superscripts differ (P<.001)- GROUP Font FEED INTAKE, kg l l l j j 1 4 7 19 13 19 19 22 25 29 DAY OF LACTATION Figure 6. Relationship of Season and Daily Feed Intake in Lactating Sows. 75 Table 9. Relationship of Sow Backfat Depth at Farrowing and Mean Daily Feed Intake in Lactating Sows. Item Fat Depth, mm <13 13-15 16-18 19-21 >21 SEM n 23 46 52 57 39 Mean Daily Feed Intake 6.35 5.75 5.555 5.3ed 5.0d .24 5- 5- °- 4 Means with different superscripts differ (P<.05). 9 snow Fe.“ snow I nus no: 7 ‘ J 0... .ae' "e". "5 0‘. e r oto'o‘m’t..°"" 7" '0 '0‘“ as“ . ‘v-«c' 1' —e— eta—e no» tau- --e- tetanu- ---e-- sauna ”‘9‘" 221- FEED INTAKE, kg l I j l I 4 l 1 4 7 10 13 19 19 22 25 29 DAY OF LACTATION Figure 7. Relationship of Sow Backfat Depth at Farrowing on Daily Feed Intake in Lactation. 76 to evaluate the relationship of sow weight and BF on feed intake. In this case sow weight was not a significant covariate indicating fat sows tend to eat less in lactation regardless of weight at farrowing. The association between sow rectal temperature on day one of lactation and daily feed intake of lactating sows was evaluated (Table 10). Sows with normal temperature, (40°C consumed significantly more feed (P<.05) in the first week of lactation than those sows with elevated temperatures (>40°C). This reduction in feed intake was observed especially the first five days of lactation (Figure 8). However, this reduction in feed intake the first week did not significantly reduce feed intake (P>.10) for the entire lactation period (Table 10). The relationship of feed intake on d1 of lactation and mean daily feed throughout lactation was evaluated (Table 11). Sows that consumed (1.4 kg of feed on day 1 of lactation had a lower mean daily feed intake during the entire lactation period than sows which consumed >1.5 kg of feed on d1 of lactation (P<.05). Sows consuming larger amounts of feed on d1 also reached greater feed intake levels more rapidly (P<.01) than sows with low intake levels on d1 (Figure 9). Thus, it appears sows that have large appetites display those appetites at the outset of lactation. 77 Table 10. Relationship of Sow Rectal Temperature on Day 1 of Lactation with Mean Daily Feed Intake in Week 1 and in the Entire Lactation. Item n 39 103 . 25 SEM Day 1 Rectal Temperature, °C <39 39-40 >40 Week 1 Mean Daily Feed Intake 4.25 4.35 2.75 .16 Mean Daily Lactation Feed Intake 5.4 5.5 5.3 .19 5- 5 Means with different superscripts differ (P<.05)o FEED mm: kg DAY OF LACTATION Figure 8. Relationship of Sow Rectal Temperature on Day 1 of Lactation and Daily Feed Intake in Week 1 of Lactation. 78 Table 11. Relationship of Feed Intake on Day 1 of Lactation with Mean Daily Feed Intake of Lactating Sows. Item n 36 77 61 42 Day 1 Lactation Feed Intake, kg (005 Des-1e4 1e5-2e3 >2e3 SEM Mean Lactation Feed Intake 5.15 5.35 5.65 5.95 .23 a. 5 Means with different superscripts differ (P<.05)- GROUP Pe.99 GROUP I RUE P¢.91 FEED INTAKE, kg -u.-. .u.. J l l l l 0 A J l 1 4 7 19 13 19 19 22 25 29 DAY OF LACTATION Figure 9. Relationship of Feed Intake on Day 1 of Lactation and Daily Feed Intake in Lactating Sows. 79 The relationship between parity and feed intake in lactating sows was evaluated (Table 12). Sows were divided into groups of parity 1, parity 2 and 3, parity 4 and 5 and greater than parity 5. Parity 1 sows consumed significantly less feed than all other parities (P<.05). Although feed consumption in parities 2 through 5 showed numerical differences they were not statistically significant (P>.11). Sows of greater than parity 5 consumed significantly more feed than all other parities (P<.05). Parity 1 sows tended to consume less feed than greater parity sows in feed intake (P<.09), especially in the first week of lactation (Figure 10). Data were evaluated to determine the association between number of pigs farrowed or number of pigs weaned on feed intake of lactating sows. No significant association between number of pigs farrowed and feed intake of lactating sows was observed (P>.10). However, feed intake of lactating sows was significantly influenced by number of pigs weaned (Table 13). Sows weaning seven pigs or less consumed less feed in lactation than all other litter sizes (P<.05). Sows with litter sizes of 8 or 9 piglets did not consume significantly' different. amounts. of feed (P>.10). Sows weaning 10 or more pigs consumed larger quantities of feed (P<.05) as compared to sows with smaller litter sizes (Figure 11). 80 Table 12. Relationship of Sow Parity and Mean Daily Feed Intake of Lactating Sows. Item n 27 89 47 53 Parity 1 2-3 4-5 >5 SEM Mean Lactation Feed Intake, kg 5.15 5.35 5.55 5.8c .12 a. 5» ° Means with different superscripts differ (P<.05)- GROUP Pa.“ O 8 fl' 8 ( .— Z D III ID IL --0— 1 2 00". 2., -0- 495 -0.-. .‘ ‘ l l l R 1 1 L j 1 4 7 19 13 19 19 22 25 29 DAY OF LACTATION Figure 10. Relationship of Sow Parity and Daily Feed Intake in Lactation. 81 Table 13. Relationship of Number of Pigs Weaned and Mean Daily Feed Intake of Lactating Sows. Item n 29 47 59 51 31 Number of Pigs Weaned 17 8 9 10 111 SEM Mean Daily Lactation Feed Intake, kg 4.55 5.35 5.55 5.75 5.95 .14 a. 5. ° Means with different superscript differ (P<.05). GROUP Pe.92 FEED INTAKE, kg J j l 1 4 7 19 13 19 19 22 25 29 DAY OF LACTATION Figure 11. Relationship of Number of Pigs Weaned and Daily Feed Intake of Lactating Sows. 82 The relationship between feed intake of lactating sows with 21 day litter weight was evaluated (Table 14). The 21 day litter weight groups of lactating sows evaluated were <39, 39-47, 48-56 and >56 kg. Significant mean differences existed between each weight group (P<.01). Sows with greater 21 day litter weights consumed more feed in lactation (Figure 12). Total feed consumed in lactation was used to determine the association of total feed intake in lactation and sow and litter performance. Sows were divided into groups using <113 , 113-135, 136-158, 159-181, and >181 kg of feed consumed during lactation. It is academic that when sows are differentiated by total feed intake in lactation mean daily feed intake in lactation will differ (Table 15). Sow groups were different (P<.003) in daily feed consumption patterns especially as noted in week 1 of lactation (Figure 13). Sow weight at farrowing did not significantly influence total feed consumed in lactation for those sows eating more than 113 kg over a 28d period. However, sows that consumed <113 kg feed in lactation weighed significantly less at farrowing than sows from all other feed intake levels (P<.05). Sows that consumed more feed in lactation lost less weight in lactation (P<.05). Total feed consumed also influenced (P<.01) rate of weight loss in lactation (Figure 14). Those same sows with less weight loss also showed less backfat loss in lactation (P<.05). Sows with greater total feed intake in lactation started 83 Table 14. Relationship of 21 Day Litter Weight with Mean Daily Feed Intake of Lactating Sows. Item n 28 48 73 68 SEM 21 Day Litter Weight, kg <39 39-47 48-56 >57 Mean Daily Lactation Feed Intake, kg 4.45 5.15 5.55 5.9d .13 5- 5- c. 5 Means with different superscripts differ (P<.01)- 7 cnoup non: .4. g""'"w‘~v1 FEED INTAKE, kg l l I. 4 1 l l L l 1 4 7 19 13 19 19 22 25 29 DAY OF LACTATION Figure 12. Relationship of Litter Weight at d21 of Lactation and Daily Feed Intake of Lactating Sows. 84 Table 15. Relationship of Total Feed Consume in Lactation with Various Sow and Litter Performance Criterion. Item n 31 Total Lactation Feed Intake, kg (113 Mean Daily Feed Intake, kg 3.95 Mean Sow Weight at Farrowing, kg 2145 Mean Sow Weight Loss, kg 18.55 Mean Sow Backfat Loss, mm 2.65 Mean Litter Weight Gain, 0'21 d, kg 3104. 34 113-135 4.45 2225 18.05 2.555 40.15 54 136-158 5.355 2275 9.55 1.35 41.45 64 159-181 6.0c 2225 6.05 .85 41.75 34 >181 6.6d 2205 2.55 .3c 46.0c SEM .15 2.04 .47 .06 .45 85 19 GROUP Pm1 GROUP I M P“ . b e 0...... ‘9 a, - 'Ae" ' . e.e .’ ... ‘3'. -- I- . g ‘ . ."""" -$:$.,,:._,_'¢ 3”... f e‘ o ‘. .‘ ..o . o o c g ’e‘ (‘74 "‘ ‘.‘0.0.e.0" . ‘ ‘ . .T‘: e ". _' e’,‘ .‘T‘ O 4 " ,If ,e' g .. '0. * 1“," u. .' no» 119-18kg . 2 " -«e— tar-teen -0’-‘ mm" “"N'. e191“ 0 A l L L l l 4 l 1 4 7 19 13 19 19 22 25 29 DAY OF LACTATION Figure 13. Relationship of Total 28d Lactation Feed Intake and Daily Feed Consumption in Lactating Sows. 90W WEIGHT, kg GROUP Pe.92 GROUP I “NE Pm! ) “”0 1 2 3 4) WEEK b Figure 14. Relationship of Total 28d Lactation Feed Intake and Sow Weight in Lactation. 86 with less backfat and showed a reduced rate (P<.001) of backfat loss (Figure 15). In addition, sows that consumed more feed in lactation had heavier litters at d21 of lactation (P<.05). Sows that were in the low consumption group ((133 kg) had significantly lighter 21d litter weights (P<.05) than other feed intake groups. Litter weights, over time, responded. differently (P<.001) in sows at various intake levels (Figure 16). Discussion Feed intake in lactating sows is influenced by many factors. The various regression analysis indicated only a modest portion of the variation in feed intake of lactation sows can be explained using variables such as day of lactation and ambient temperature (R2 = .22). By using information only obtainable in lactation such as sow weight change in lactation, 21 d litter weight, number of pigs nursed and feed intake on d1 of lactation, the amount of variation that can be explained by the regression is raised to 43%. With all the information available and the numbers of observations used this represents a small portion of the variation in daily feed intake explained (O’Grady et al., 1985, NRC, 1987). With greater standardization of genetics in the sow herd, an improved environment in the farrowing facilities, and more sophisticated data gathering techniques a larger portion of the variation in feed intake of lactating sows should be explainable. 87 FAT DEPTH. mm GROUP van GROUP I “BE PcM1 Figure 15. Relationship of Total 28d Lactation Feed Intake and Sow Backfat Depth in Lactation. 70 GROUP P¢.001 GROUP I THE ram .0 L .3 3 w" 50 " J F at,“ z I” k as" g “ ' 'or:’ 3 ,9 5 a’:” do I t a . '0'.:” ..o. I ".5, - ”-0-- 113-tau 20 - ..-;'J"’ -1I- an“ a. * 3:9" ---o-- 1.401 In. ""G" 91.1 h ‘0 L j 1 2 3 4 WEEK Figure 16. Relationship of Total 28d Lactation Feed Intake and Litter Weight in Lactation. 88 Mean daily feed intake for all observations increased throughout the 28 day lactation period. This is consistent with studies by Smith (1959), Lodge (1961) and O’Grady (1985). Ambient temperature has a dramatic influence on feed intake in lactating sows. A 25% decrease in feed intake as farrowing room temperature increased from <22'C to >25'C was observed (Figure 17). This is consistent with findings of Lynch (1977). Daily low temperature showed a similar relationship with feed intake as daily high temperature. However, differences in mean daily feed intake were more highly related to daily low temperature than daily high temperature. Therefore, patterns of feed consumption are altered in sows exposed to high ambient temperatures. Sows lactating in high (>27'C) temperatures and then exposed to either >24'C or (24°C for average low temperature consumed significantly different amounts of feed consumption in lactation. Those sows that were exposed to cooler temperatures were able to compensate intake levels during the cool period and maintain a higher overall lactation feed intake level. Therefore, efforts should be made to allow sows to get cool for at least part of a 24 hour period to maintain adequate feed intake levels. Sows lactating in summer months showed a larger depression in lactation feed intake than sows observed in the cooler months of the year. This is consistent with data published by O’Grady (1985) and Britt (1986). Ambient MEAN ONLY FEED INTAKE, kg 4.6 S 22°C 22-20'0 2 20°C TEUPERATURE '0 Figure 17. Relationship of Ambient Temperature and Mean Daily Intake in Lactating Sows. 90 temperature was a significant covariate, however, it did not totally eliminate season effects. Therefore, other factors such as day length, humidity or other unidentified factors may' influence feed intake of lactating sows during the summer months. Sow backfat depth at farrowing also influenced feed intake in lactating sows (Figure 18). This is consistent with findings of Lodge et al. (1961) and O’Grady et al. (1985). Sows with more backfat at farrowing consume less feed in lactation. Sows that are too thin at farrowing may be more susceptible to injury and premature culling from the herd. (Aherne and Kirkwood, 1985; Tubbs, 1988). A sow capable of 8 kg of milk per day that came into lactation with a very minimum of body reserves (<10 mm backfat) and consumed 6.5 kg feed/day would be in a negative energy balance (NRC, 1988). A sow with the same milk production capabilities and 18 mm of backfat may not consume as much feed in lactation but could conclude lactation with more body fat thus improving her longevity opportunities. The scenario would be similar to situations seen in the industry today where sows are not in the proper body condition at farrowing and lose too much body weight in lactation. Ovarian function can be impaired and injury and culling rates rise to unacceptable levels (MacLeen, 1968; Close and Cole, 1986). In addition, milk yields and therefore piglet growth will not be maximized in situations where sows are in 91 0.5 a ‘ In. 8 ‘ E 0.0- 0 III ID IL ,- =." ( O 5.5" 2 ( III a so 1 l I l ' 11 14 17 20 23 FA‘I’ DEPTH, lull Figure 18. Relationship of Sow Backfat Dpth at Farrowing and Mean Daily Feed Intake in Lactating Sows. 92 a negative energy and protein balance (V‘erstegen et al., 1985; Wittemore, 1987). Rectal temperature on day 1 of lactation showed a significant influence on week 1 feed intake of lactating sows. Sows with elevated body temperature on d1 had reduced in feed intake until day 5 of lactation. These sows did return to normal feed intake by d6 of lactation and had similar feed intake to sows not displaying elevated temperature on d1 of lactation for the remainder of lactation. However, lactation intake for week 1 was depressed as a result. Although sow temperature has been shown to affect lactation performance (Funiss, 1987) this information showing a depression in week 1 feed intake is unique. Data of day 1 feeding level (Figure 9) indicated that sows with big appetites eat immediately after farrowing. Sows that consumed less feed on d1 were slower in gaining high feed intake levels and did not consume as much total feed in lactation. In the current and previous work (Mahan, 1977; O’Grady, 1985; Britt, 1986), as parity increases, lactation feeding level is elevated. Several factors such as metabolic body size, litter size, milking ability and culling of unproductive sows from the herd all favor higher feed intake levels for the older heavier sows. Data from this study are consistent with these theories (Figure 19). 93 5.7 I a 8 III . x 5.5 E 8 E 5.5 - > :3. ‘ O z 54‘- ( “J s 5'3 s 130 kg 131-204 kg 205-223 kg 2 227 he DOW WEIGHT, kg Figure 19. Relationship of Sow Weight on d1 of Lactation and Mean Daily Feed Intake in Lactating Sows. 94 Litter size and litter weight gain are correlated positively with milk yield in lactating sows. Sows with 11 or more pigs consumed almost 30% more feed than sows with 7 or less pigs (Figure 20). A similar effect was seen as 21 day litter weight increases from 40 kg to 60 kg. Those sows producing the heaviest 21 day litter weight consumed 25% more feed than those sows with the lightest litter weights (Figure 21). When total lactation feed consumption is used to determine the relationship with sow and litter performance criteria several observations can be made. Sow weight did not provide a major influence on total feed intake in lactation. However, statistical differences may be seen if adequate replication of the trial were accomplished. As total lactation feed intake increased, loss of weight and backfat in lactating sows was reduced. In addition, sows that consumed more feed in lactation had heavier litters at d21 of lactation. The question to be answered is which is the driving factor? Does the catabolic activity of lactating sows have an inhibitory effect on feed stimuli? Nutrient demands of lactating sows were met by utilizing feed components as well as the results of catabolic activity in the sow. Therefore, the reduction in blood levels of glucose, protein and fatty acids should cause an increased need for the sow to consume more feed. Increased lactation 95 GD 5 3' u? .. x as E a E 5.0’ ,- s < o 4 z 4.5" < m I 1°57 s 2 10 211 LITTER SIZE Figure 20. Relationship of Litter Size Weaned and Mean Daily Feed Intake in Lactating Sows. 0.0 ) u 8 III 8 {5 D I“ I“ IL > d 3 so} 2 ( I“ a I “s an kg 4049 kg 50-59 kg 2 59 kg 21 DAY LITTER WEIGHT Figure 21. Relationship of Litter Weight at d21 of Lactation and Mean Daily Feed Intake in Lactating Sows. 96 stimuli and heightened demands for milk precursors probably increases the need for sows to increase feed intake. Conclusions Daily feed intake in lactating sows is highly variable and influenced by many factors. Regression analysis of these data indicate only a modest amount of the variability in daily feed intake can be explained. Warm ambient temperatures dramatically reduce feed intake levels of lactating sows. Sows exposed to hot temperatures during the day can maintain near normal feed intake levels if they are allowed a cooling off period. The greatest impact of warm temperature is seen in summer months. As sow weight and parity increased, feed intake increased. Elevated rectal temperature on day 1 of lactation reduced feed intake in the first week of lactation. Day 1 feed intake reflect lactation feed consumption levels. Litter size and sow milking ability as reflected by 21d litter weight are positively related to intake level of lactating sows. Therefore, enviromental and managerial factors can greatly impact feed intake of lactating sows, most in a negative manner. In addition, feed intake can directly affect sow and litter performance in lactation” Direct control of environmental temperature can greatly enhance feed intake of lactating sows. PToper management of sow body condition during the preceeding gestation period can greatly enhance feed intake in 97 lactating sows. Maintaining proper’ heal status in the breeding sow herd can improve lactation feed intake. As a result of improved management practices and lactation environment, sow body weight and composition change can be minimized and litter weight gain can be enhanced in lactating sows. EXPERIMENT II Gastric Cannulation of Pregnant Sows Introdnotion Cannulation of the gastrointestinal tract has been used for various nutritional studies in swine (Gargallo and Zimmerman, 1980; Markowitz et al., 1964; Daugherty, 1981; Pekas, 1983; Hamilton et al., 1985). Digestibility and utilization of nutrients has been more clearly understood using cannulation sites from the stomach to the large intestine. Cannulas allow sample collection of intestinal contents and gastric or intestinal loading (Gargallo and Zimmerman, 1980, 1981; Pekas, 1983; Hamilton et al. 1985). Feed intake beyond that of ad libitum levels (superalimentation) has been demonstrated in growing pigs by means of gastric cannulae. Pigs fed in excess of ad libitum, with all feed intake accomplished through the cannula, displayed a significant increase in growth rate (Pekas, 1985). Many materials have been used for gastrointestinal cannulation (Markowitz et al., 1964; Gargallo and Zimmerman, 1980; Dougherty, 1981; Pekas, 1983; Hamilton et al., 1985). For lactating sows, the cannula must be strong, flexible, resilient and able to withstand the sow rubbing the cannula, as well as frequent piglet contact with the cannula. In addition, the cannulation procedure and cannula must not 98 99 inhibit the ability of the sow to have normal lactation function. Feeding sows entirely through the cannula must not compromise gastrointestinal function or normal lactation ability. Lactational requirements of high producing sows are in most cases greater than what the sow will consume on an ad libitum basis. These sows will lose excess weight during lactation with adverse effects on subsequent reproductive performance (Aherne and Kirkwood, 1985; O’Grady, et al., 1985). The cannulation procedure was developed to allow feeding of sows during lactation in excess of ad libitum. Sows were evaluated on their ability to utilize these additional nutrients as measured by milk yield, body weight change and nutrient digestibility. MstorileandJsthods BMW - Silastic‘ tubing (16 mm i.d. 22 mm o.d.) was chosen for the cannula due to its strength, flexibility, and histocompatibility. Cannulae were assembled with a 15 cm section of tubing for the base and a 30 cm section of tubing for the barrel. A small, oval section (25 mm x 10 mm) was removed from one side, at the center of the base section (25 cm). One end of the barrel section (30 cm) was placed in the oval opening of the base at a slight angle (60-75 degrees). The angle allows the ‘ Silicone Medical grade tubing, American Scientific Products, McGew, Il. 100 cannula to exit the animal at a near 45 degree angle which facilitates the feeding process. After joining the barrel and base sections, they were secured with medical silicone adhesives and allowed to cure for 24 h. The base section, on the opposite side of the barrel, was split and approximately 30% of that base wall removed. This dispersion of feed into the gastric lumen and yet allowed retained rigidity of the tubing. A second application of silicone adhesive was made on the inside of the barrel base junction and allowed to cure for 24 h. All sharp and pointed edges were trimmed and rounded to avoid trauma to the gastric mucosa. Cannulae were packaged individually and sterilized with ethylene oxide and aerated prior to surgery. finngigal_pzooednrg - Twelve Yorkshire and 12 crossbred, pregnant (d85 1 5d), multiparous sows weighing 200 to 225 kg were fasted for 24 h before surgery. Each sow was injected intramuscularly (IM) with azaparone6 at 2.2 mg/kg (maximum dose 200 mg) and ketamine hydrochloride" at 8.8 mg/kg in combination. Sows were left undisturbed for 20 minutes to maximize the effect of premedication. A 20 gauge 32 mm catheter was placed in an ear vein and 5% thiamyal sodium8 Medical Adhesive Silicone, Type A, Dow' Corning Corp. Midland, MI. ‘ Stresnil - Pitman-Moore, Inc. Washington Crossing, NJ. 7 Ketaset - Bristol-Myers, Co. Syracuse, NY. 9 Bio-Tal - Bio-Ceutic, St. Joseph, MO. 101 was administered intravenously (i.v.) at 22 mg/kg to induce anesthesia and allow intubation of the trachea. A tracheal tube was inserted by placing the sow in sternal recumbency and. extending the head with ‘the aid of a hog snare”. Manipulation of the soft palate and epiglotis with the end of the tracheal tube allowed direct visualization of the arytenoid cartilages. Supplemental lighting was used to enhance the visualization. Passage of the endotracheal tube into the trachea was accomplished by gently moving the tube posteriorly and twisting simultaneously. Anesthesia was maintained with 2.5% halothane and oxygen in a semi-closed circular system. Sows were placed in right lateral recumbency and the left abdominal wall was clipped, scrubbed, and prepared for surgery from rib 7 to the tuber coxae and from the dorsal midline to 50 cm from the midline. An incision was made in the 11th intercostal space beginning 20 cm from the dorsal mid line and extending approximately 20 cm caudal-ventral. Separation of the muscle layers and peritoneum were accomplished using sharp dissection. Ribs were separated using finnochietto rib spreaders. The spleen was visible through the incision and the stomach was palpated anterior and medial to the spleen. The spleen was moved posteriorly and the stomach was grasped and gently exteriorized using vulsellum forceps. Saline soaked towels were packed around 9 Ring-o-Matic hog catcher, MASCO, Fort Atkinson, WI. 102 the exposed portion of the stomach which attenuated peritoneal contamination. A purse string suture approximately 4 cm in diameter using #2 polyglycolic acid10 was place in an avascular area of the dorsal greater curvature in the gastric wall. The cannula base was folded and both ends of the base were inserted simultaneously into the incision. The purse string suture was secured, and a second. purse string suture of #2 polyglycolic acid was placed in the gastric wall around the barrel of the cannula. The cannula was manipulated through the stomach wall extending the base to its original T shape. The cannula was exteriorized through the 10th intercostal space using a stab incision of the abdominal wall including the peritoneum. Care was taken when making the exit incision to avoid lacerating any viscera. A.pean forcep was passed through the stab incision and the end of the cannula was grasped and exited with a twisting motion. The cannula was palpated through the gastric wall to allow positioning of the cannula to angle upward at approximately a 45 degree angle. The exit through the peritoneum was at least 5 cm from the original incision to allow ease of suturing the abdominal wall. The abdominal wall was closed in four layers beginning with the peritoneum in a continuous pattern using #2 polyglycolic acid. Abdominal muscles were closed in two layers using #2 polyglycolic acid also in a 1° Dexon - David Geck, Manati, P.R. 103 continuous pattern. The skin was sutured with #1 polyamide11 using a Ford interlocking pattern. The stomach was positioned in contact with peritoneum to allow formation of adhesions between the gastric wall and abdominal wall. Adhesive tape was wrapped around the cannula to 2 cm thickness to prevent pulling the cannula into the abdominal cavity. Folding of the exteriorized cannula and taping eliminated any flow through the cannula. Recovery took place in smooth sided, 2.4 m x 2.4 m, bedded pens until 7d prepartum at which time the sows moved to the parturition area. The parturition stalls were equipped with solid stainless sides to prevent accidental extraction of the cannulae. Six million units of benzathine penicillin G” was given postoperatively once IM. The surgical site was dressed with a topical ointment13 for one week postoperatively . The skin sutures were removed 2 weeks postsurgically. All primary incisions healed by first intention. The sows were maintained on a corn-soybean fortified diet (Table 2) orally until parturition at which time all feed was introduced via the cannulae. 11 Breunamid - B. Braun, W. Germany. 12 Benze-Pen, Beecham Laboratories, Bristol, IN. 13 Nitrofurazone, NORDEN Labs., Inc., Lincol, NE. 104 Data were analyzed using General Linear Models for least squares analysis of variance. Mean separation for cannulated vs non-cannulated sows was accomplished using Student’s t statistic. All means reported are least square means. The standard error of the mean reported is pooled. Rosalia Gastric cannulae were successfully placed in 24 pregnant sows at day 85 i 5 d of gestation. Twenty-two of 24 sows ate normal meals within 24 h of surgery and 11 sows ate normal meals within 36 In all sows were selected for this study on the basis of prior lactation performance. Three cannulae were lost during the course of the trial. However, within 12 h after extraction, cannulae were replaced by insertion through the patent wound in the abdominal wall. No abortions were observed in cannulated sows. Incidence of mummified fetuses and stillborn piglets were not different for cannulated vs. non-cannulated sows (P>.10). Parturition was similar in duration for treatments and litters were standardized to 10 pigs. All pigs nursed within 24 hours after birth. Piglet birth weight and weaning weights were similar for all sows. After weaning, sows exhibited normal rebreeding intervals (Table 16). Four sows ‘were maintained. with functional cannulae through a second gestation and lactation. 105 Table 16. Effects of cannula placement in pregnant sows on reproduction and lactation performance. Cannulated Non-cannulated Item i i S.E. No. sows 18 11 No. born alive/litter 10.90 10.20 .56 No. stillborn/litter .72 .82 .42 No. mummified fetuses/litter .22 .18 .12 No. nursed/litter 10.00 10.00 No. weaned/litter 9.94 9.64 .15 Ave birth wt. (kg)/pig 1.39 1.41 .31 Ave weaning wt. (kg)/pig 5.75 5.68 .56 Days to estrus 4.9 4.64 .24 106 Disonssion Gastric cannulation is a useful tool in addressing various nutritional and metabolic questions. In addition, superalimentation through gastric cannulae provides situations for the study of nutrient utilization and gastrointestinal biological and. microbiological function. This method appears to allow normal sow function of parturition and lactation. In addition, the capability of feeding precise amounts of predetermined nutrients versus ad libitum may allow more accurate measurement of response criterion. EXPERIMENT III Effects of feeding lactating sows in excess of ad libitum on lactation performance, nutrient balance and sow weight and body fat change. .Intzodnotion Most lactating sows with high production levels experience negative energy balance when they reach peak milk yields (ARC, 1981; Noblet and Etienne, 1986; Whittemore, 1987). Stimuli for feed intake do not induce feeding levels at which energy intake equals energy requirements. In some cases this negative energy balance results in excess body weight loss and concomitant cessation of ovarian function (Reese et. al., 1982; King and Williams, 1984; Aherne and Kirkwood, 1985). Ad libitum feeding of sows with small litter size or minimal milk production results in net weight gain during the lactation period (Lodge, 1959; Whittemore, 1987). Average piglet size at weaning is greater for pigs from small versus large litters (Lewis et al., 1978; Verstegen et al., 1985). Therefore, substrates used for milk synthesis are more readily available to functioning mammary glands which results in greater milk output per functional gland. Limited feeding levels in high producing lactating sows has been shown to reduce milk yield (Noblet and Etienne, 1986). Feeding growing pigs in excess of ad libitum has been described by Pekas (1983, 1985). Increasing feed intake in 40 Kg pigs 20% beyond litter mate ad libitum intake levels, via a gastric cannula, resulted a 39% increase in daily 107 108 gain. Feed required per pound of gain was reduced slightly (7%) while composition of gain was unchanged (Pekas, 1985). Therefore, a major component in limiting rate of body weight gain in growing pigs is the limitation of meal size and meal frequency. Pekas (1985) concluded that capacity for digestion and absorbtion of nutrients was not limiting in pigs, but rather the most limiting was feed intake. If this model could be applied to lactating sows, would the same conclusions be made? Would extra nutrients be utilized to increase body weight, increase milk yield or both? Feeding lactating sows in excess of ad libitum has not been described in the literature. This study was designed to determine if feeding high producing lactating sows, that would normally be in a negative energy balance, to a level beyond ad libitum feed intake would improve lactation performance and reduce body tissue catabolism. Our primary objective in this experiment was to determine effects of feeding lactating sows in excess of ad libitum. These effects were measured in body weight and body fat changes, selected blood metabolite and insulin levels, milk yield and litter weight gain of lactating sows. A second objective was to determine digestive and absorptive capacity of lactating sows fed in excess of ad libitum. Motorislunuothods AnimaLJsrandJanassmsnt. The high producins Bows used in this study were selected on the basis of previous 109 lactation performance. All sows had weaned at least 9 pigs with a 21 day litter weight of >55 kg. These sows were allotted randomly to one of three experimental groups. Individual sows in two of these sow groups were fitted with a gastric cannula at day 85 i 5d of gestation. The surgical procedure, postoperative care and surgical effects on sows are described in the Experiment II. Sows were brought into the farrowing facility at day 107 1 2d of gestation. A gestation diet (Table 17) was fed until farrowing at 2.3 kg/d. Sows were housed in crates .62m x 2.15m with the bottom bar of the crate bowed out .15m allowing the sow more room for lateral recumbancy. An area of 1.66m? on the sides of the crate provided space for piglets. Heat lamps at the rear of the crate were provided for piglets at farrowing. This heat lamp was moved to a hover located at the front of the farrowing crate 24 h after parturition. Room temperature was maintained as close to 21'C as possible in a mechanically ventilated environmentally controlled farrowing facility. The flooring was 3 ga. wire mesh with manure removed from the facility via a pull plug Y gutter system. Two identical rooms were used for the experimental replication beginning April 25, 1988 and ending November 10, 1988. No differences were seen in performance due to farrowing room. Farrowing groups were sequenced every three weeks. The period from July 28 to September 20, 1988 was not used due to excess summer 110 Table 17. Composition and Calculated Analysis of Diets. Diets Ingredient Gestation X Lactation Corn 70.45 75.95 Soybean Meal 14.50 17.35 Wheat Bran 10.00 Corn Oil 3.00 Mono-dicalcium Phosphate 2.00 1.35 Calcium Carbonate 1.30 1.25 Salt .50 .25 Vit.-Trace Mineral Premix‘ .60 .60 Vit.E-Selenium Premixb .50 .25 Choline Chloride, 50X .15 TOTAL 100.00 100.00 OslonlsLod_Analxsis Metabolizable Energy (ME), Kcal/Kg 2996 3368 Crude Protein X 14.0 14.10 Lysine, X .64 .69 Calcium, X .92 .78 Phosphorus, X .80 .61 ‘ Composition was: Vitamin A, 661,380 IU; Vitamin D3, 132,276 IU; Menadione, .66g; Riboflavin, .66g; Niacin, 3.53g; D-Pantothenic acid, 2,64g; Choline, 88.18g; Vitamin B12, 3.96mg; Zn, 7.5g; Mn, 7.5g; I, .11g; Cu, 2.0g; Fe, 12.0g/kg Premix. 5 Composition was Vitamin E, 3310 IU; Selenium 19.8 mg/kg Premix. 111 temperatures. A total of 12 replications and 36 sows were assigned to treatments in this study. Treatment groups were: (1) non-cannulated control, (2) cannulated control, and (3) cannulated sows fed in excess of ad libitum levels or superalimentated sows. Positive controls (NC) were non-cannulated (n = 12) sows, fed ad libitum throughout lactation. A second treatment group was the control cannulated (CC) gastrically cannulated (Experiment 11) and received all feed through the cannula postpartum (n = 12). Feeding level for the first 10 days of lactation was adjusted daily to match the daily feed intake curve of high producing sows (Experiment 1). Day 10 through day 28 of lactation, feed intake was calculated to be 110 kcal DE-kg BW0-75 for maintenance requirements plus 2 Mcal DE/kg of milk produced. It was assumed that sows were in the high milk yield range and thus NRC (1988) recommendations of 7.5 kg daily milk yield were used to determine feeding level. Superalimentated (SA) sows were the final treatment group (n = 12). These sows were gastrically cannulated in gestation (Experiment II) and fed orally until parturition. At farrowing SA sows were fed entirely through the cannula. Feeding level for the first 10 days of lactation was adjusted daily to match the daily feed intake curve of high producing sows (Experiment I). Day 10 through day 28 of lactation, sows were fed a level equal to 110 Kcal DE'kg BW0-75 for maintenance, 2 Meal DE/kg milk yield (7.5 kg milk/day) per day plus an additional 112 amount equaling 40X of the amount required for high levels of milk yield. This level approximated a 20X increase in total energy intake level for SA sows compared to CC sows. As the first sow in each replication farrowed, the remaining five sows were induced to farrow with an intramuscular injection of prostaglandin F2 ' (PG F2 ‘0.14 In all cases, the remaining sows farrowed within 36 hours of the first litter farrowed in that replicate. Ldtter size was standardized to 10 pigs within 24 hours after parturition. However, if a piglet was crushed or injured during week 1 of lactation the piglet was replaced. Piglets were not fed a supplemental ration, however NC pigs had limited access to the dams ration. Within 24 hours of farrowing sows were weighed and probed ultrasonically for backfat depth.15 Daily measurements were made for average high and average low room temperature . 1 ‘5 Daily rectal temperatures were recorded for sows . 1 7 Temperature measurements were taken at 0800b. Gastric cannulation did not affect normal sow activity (Experiment II). All sows had unlimited access to water by means of an automatic nipple waterer. All treatments received the same lactation diet at feeding level described previously (Table 17). Non cannulated control sows were fed twice daily at 1‘ Lutalyse, Upjohn Company, Kalamazoo, Michigan. 15 Leanmeter, Renco, Inc. Mason City, Is. 1° Lab Systems, Inc. Berkley, Ca. 17 Agricultural Electronics, Montclair, Ca. 113 0800 and 2000 h. Orts were recorded at 0800 daily. Cannulated sows were fed twice: daily with. total intake divided equally between morning and evening feedings (0800h and 2000b). Water was mixed with feed at a 4:3 weight ratio. This feed and water mixture was then pumped through the cannula using a hand driven sausage stuffer.” The sausage stuffer and cannula were linked together using flexible clear tubing.” Weight of the feeding apparatus plus feed mixture was taken before and after feed delivery to determine total alimentation level.20 Weekly measurements of sow weight, backfat and litter weight were taken as described in Experiment I. In addition, blood was sampled weekly via jugular vena puncture at 0700h or 12 hours after last feeding. Blood was collected in evacuated 10 ml tubes, allowed to clot for 24 hours and centrifuged at 2500 rpm. Serum was collected and stored at -20'C until further analysis. An additional 3 ml of blood was collected in evacuated tubes containing anticoagulant (potassium oxalate) and glycolytic inhibitor (sodium fluoride) for glucose analysis. Plasma was collected after centrifugation and stored at -20’C until glucose analysis could be accomplished. Estimation of milk yield was accomplished on d 7, 14, 21, and 28 of lactation 1‘ Riddick 001., Philadelphia, PA. 1’ Tygon, Norton Plastics and Synthetics Division, Akron, Ohio. 3° International Computing Scale, New York, NY. 114 using nine hourly we igh-suckle-weigh measurements . Procedures used were similar to those described by Lewis and Speer (1978), Speer and Cox (1985) and Noblet and Etienne (1986). Piglets were separated from sows to heated stalls 1 hour prior to initiation of weighing. Piglets were moved out of the stalls and onto damp, cool concrete to encourage urination and defecation. Piglets were divided into two groups of 5 piglets per group and identified. Piglets were then weighed to the nearest 5 gm and placed with the sow for suckling. Upon completion of the nursing process pigs were quickly regrouped and weighed and weight change was recorded. Adjustments in weight were made for urination and dunging while in the nursing period (Speer and Cox, 1984). The entire weigh-suckle-weigh process took about 7 minutes per litter per hour. The litter was removed from the sow at 0600b, and the first weights were taken 1 hour later with subsequent measurements following in one hour intervals. The day after estimation of milk yield, milk was sampled for composition deterioration. Pigs were separated from the sow for approximately 1 hour prior to sample collection. An intramuscular injection of 40 USP units of oxytocin was given to the sow to be collected. Milk was expressed from the first three anterior nipples on one side of the sow to obtain 50 ml of milk. Samples were stored at -20'C until further analysis. At weaning sows were moved to an enclosed, environmentally controlled breeding facility and housed in individual crates. Sows were fed 2.2 kg per day 115 of the gestation ration (Table 17). Each sow was exposed to a mature boar daily until estrus was displayed. Days from weaning to estrus were recorded. Energy balance of lactating sows was determined during two periods of lactation, days 8 through 12 and days 22 through 26. Procedures were adapted from Diggs (1965), Vestegen et al. (1985) and Noblet and Etienne (1986). Foley catheters (16 Fr.) were installed in the bladder of each sow on day 8 and 22 of lactation. Urine was collected in containers with 150 ml 6N HCl every 8 hours and the urine volume was measured every 24 hours. A 100 ml sample of urine was taken daily from each sow and stored at -20°C for later analysis. The rear half of each farrowing crate was covered with a solid rubber mat to accomplish feces collection. Feces from sows were collected every 4 hours for 24 h from d7 to 14 and d21 to 28, with the exception of one collection not performed at night. Each day a composite 1000 g sample of feces was oven dried and stored at -20'C for future analysis. WW Determination of Plasma glucose levels were made using the colorimetric procedures.“ NEFA concentration were then determined using optical density at 550 nm. 31 Glucose (Trinder) procedure no. 315, Sigma Chemical Company, St. Louis, MO. 116 Serum porcine insulin levels were determined by heterologous double antibody radioimmunoassay with methods described by Villa-Godoy (1987) and validated for porcine by Johnston (1988). Dilution of antisera (1" antibody) to 1:30,000 in guinea pig control sera22 (1:400 in .05M EDTA- phosphate buffered saline; pH 7.0) at a 200 1’1 amount per tube provided 31X specific binding of 125I-insulin and was used for assay procedures. Standard curves were obtained using .025, .05, .10, .15, .20, .30, .40, .50, .60, 1.00, 2.00, 3.00, 4.00 ng porcine insulin per tube. The standard curve used for data analysis had a coefficient of determination of .998. The intra-assay coefficient of variation was 6.9X and the lower limit of sensitivity was .125 ng porcine insulin/ml. Milk samples were thawed and thoroughly mixed prior to laboratory analysis. Samples were analyzed for dry matter and ash using AOAC methods (1975). Milk protein was determined using micro-kjeldahl methods (AOAC, 1975). Milk fat was determined using AOAC (1975) procedures adapted by Loudenslager (1984). Milk energy' was determined in an adiabatic bomb calorimeter23 on 5 g milk samples previously freeze dried. Lactose was obtained by subtracting fat, protein (Nitrogen x 6.38) and ash from dry matter. 3’ Gibco, Grand Island, New York. 33 Parr Instrument, Co. Moline, IL. 117 Feed, feces and urine were analyzed for gross energy via the adiabatic bomb calorimeter method. In addition, samples of each component were analyzed for Nitrogen using micro-kjeldahl methods (AOAC, 1975). Statistioa1__Analxsia. Measures of sow lactation performance for the three treatment groups were compared using the General Linear Models procedure (SAS, 1982) for least-square analysis of variance. The experimental design was a split-plot with repeated measurements in time (Gill and Hafs, 1971). The linear model which describes the observed responses is: Yijk = M + T1 + A(i)j + Pk + (TP)ik + E(11k), Where Yijk = Observed measurement; M = Overall mean; T1 = Treatment effect i=1, 2, 3; A(1)g = Effect of animal j within treatment 1, j=1...n; Pk = Period K: 1...5; (TP)ik = Interacting of treatment and periods; E(ijk) = Residual error. Analysis of variance and comparison of means were accomplished according to Gill (1978a, 1986). Comparisons of' main effects and of treatment means ‘within sampling period were made using Bonferroni t test. Comparison of treatment trends between specified measurement periods were evaluated according to Gill (1986). All means reported are least squares means. 118 Rosalia The experimental design for the study required 12 sows per treatment. Data from one sow in the NC group was determined to be an outlier (p<.01) using procedures from Gill (1978a). Three sows in both CC and SA groups died during the trial. All expired sows were in their third week of lactation. Necropsy reports showed no disease problems and gross diagnosis on. 5 of 6 sows indicated hyperthermia. Increased feeding levels will result in greater heat increment (Whittemore, 1987) and requires the sow to dissipate the additional heat. The test periods involved were in June and July during which Michigan experienced extreme heat of >37'C during the day and not less than 27'C during evening hours. As a result, part of the experiment was delayed until cooler fall weather arrived to complete trial replication. One SA sow died as a result of peritonitis due to gastric content leakage into the peritoneum. The net result of these losses was unbalanced number of observations of 11, 9, 9 for NC, CC, and SA treatment, respectively. Sow body weight and sow backfat measured 24 h post partum were not different (P>.10) between treatment groups (Table 18). In addition, litter size at weaning and days to return to estrus were not affected by feeding level (Table 18). Feed intake levels for the three treatment groups were different (p<.01) for the entire lactation period (Table 119 Table 18. Effects of Feeding Level on Lactation Performance. Item NC CC SA Number of observations 11 9 9 Body weight at farrowing, kg 226 217 210 Mean daily feed intake, kg 5.4d 5.9b 7.1c Lactation weight change, kg -12.lb -6.75b 10.28c Backfat at farrowing, mm 17.0 16.9 16.6 Lactation backfat change, mm -1.2b -.53b 1.1c Litter size at weaning 9.6 9.7 9.9 Litter weight gain gd 1590b 1776d 2078' Days to rebreed 4.4d 4.5d 4.7d SEM‘ 7.2 .68 4.1 .35 .04 .11 357 .14' ‘ Pooled standard error of mean. 3 ° Means with different superscripts differ (P<.01). d ' Means with different superscripts differ (P<.05). 120 18). In addition, there was a treatment x time interaction (p<.05) as a result of the various treatment feeding schedules. There were no differences in feed intake between treatments for the first week of lactation as the cannulated treatments were fed levels equal to high producing sows in Experiment I for week 1 of lactation. However, for weeks 2, 3 and 4 (p<.01) SA sows had greater feed intake levels than CC and NC sows (Figure 22). Sows in the NC and CC groups lost more weight (p<.01) and backfat (p<.01) over the lactation period as compared to SA sows (Table 18). Weight change was not different for CC vs. NC sows during lactation (Table 18). Sow weights in lactation showed significant change over the 28d period (Figures 23 and 24). Sow weight change during week 1 of lactation was not different for NC and CC sows or for CC and SA sows (Figure 24). However, weight change was seen (p<.07) between NC and SA sows during week 1 with NO sows losing more weight. In each subsequent period, week 2, 3 and 4, there were differences in weight change between NC and SA sows with NO sows losing weight, while SA sows gained weight (p<.001). Differences in weight loss was also evident in NC versus CC sows day 28 (P<.05), with NC sows losing more weight but not at days 14 and 21. Backfat change was not different (P<.05) among treatments in week 1 of lactation. Backfat measurements and backfat change was not different for NC and CC sows in lactation (Figures 25 and 26). Sows in the SA group showed 121 1o nuran nnxlwsran 3" ”00309000009009- and 5 ' U232g°‘°‘°‘°'°°O-o-°'O-o-O°o-o-o-o-o-o-o- I p o l l 4 7 10 13 10 10 22 25 28 DRY OF LACTATION l l 1 Figure 22. Mean Daily Feed Intake of NC, CC, and SA Sows in Lactation. 122 WEIGHT, kg Figure 23. Mean Weight of NC, CC and SA Sows in Lactation. 6 TRT '1-01 ’-" o-"' sow m CHANGE, kg WEEK Figure 24. Mean Weight Change of NC, CC and SA Sows in Lactation. 123 BACKFAT, mm l l 1 2 8 4 5 WEEK 15 Figure 25. Mean Last-rib Backfat of NC, CC and SA Sows in Lactation. 0.6 nu mu m ‘ “as "3 ’D --------- :+ I’ —s— an --o-- co -o- a DAGKFAT CHARGE, mm Figure 26. Mean Last-rib Backfat Change of NC, CC and SA Sows in Lactation. 124 significant increases in backfat vs. the NC and CC groups in weeks 2, 3 and 4 of lactation with NC and CC sows losing backfat. In addition, there was a treatment by time interaction (P<.05) due to SA sow increasing in backfat depth. and NC and CC sows losing backfat, indicating a different rate of fat depth change over the lactation period. SA litter weights were not different from NC or CC treatments at day 0 and day 7 (p>.10). Mean daily litter weight gain was greater in SA sows (p<.05) than in the NC and CC groups (Table 18). Litter weights were not different for NC and CC sows at any of the measured times (p>.10) (Figure 27 and 28). Litter weights of SA sows were significantly increased (p<.05) in day 14, 21 and 28 as compared to NC and CC litter weights (Figure 27). Treatments responded differently over the lactation period (p<.01). Mean daily milk yield, as measured by the weigh-Buckle- weigh technique was significantly greater (p<.05) for SA sows as compared to NC and CC sows in the lactation period (Table 19). SA milk yield was greater than the CC sows only at week 2 (p<.05) (Figure 29). But, SA milk yield differed from NC sows at days 14, 21 and 28 (p<.05) (Figure 29). Correlations between milk yield and litter weight gain were positive and significant (p<.01). Within treatment correlations were r=.76, r=.84, r=.79 for NC, CC and SA treatments, respectively. Regression equations for effects 125 WEIGHT, kg 1"o 1 2 3 4 WEEK Figure 27. Mean Litter Weight of NC, CC and SA Sows in Lactation. 105.-.. ~~ ‘~~.~ _.- n ‘s- «o» co 1. p .....q‘~~ -O- u ....... “‘ ~“‘ “W$¢O'... . “D ---------- 12 10 LITTER m CHANGE, kg . I TRT Po.” TRT 2 T'IUE Pa.“ Figure 28. Mean Litter Weight Change of NC, CC and SA Sows in Lactation. 126 Table 19. Effect of Feeding Level on Milk Yield and Composition. Item Treatment NC CC SA SEMa Number of observations 44 36 36 Milk yield, Kg/d 7.8b 8.2b 8.6c .92 Milk energy content, Kcal/Kg 1129 1119 1110 66.3 Dry Matter, X 18.7 18.4 18.6 1.01 Ash, X .79 .78 .78 .14 Protein (Nx6.38). X '5.41 5.29 5.31 .71 Fat, X 7.42 7.12 7.46 .35 Lactose, X 5.09 5.21 5.05 .69 ‘ Pooled Standard error of the mean. 5 ° Means with different superscripts differ (P<.05). WEIGHT, kg Figure 29. Mean Weekly Milk Yield as Measured by the Weigh- suckle-weigh Method of NC, CC an SA Sows in Lactation. 127 of milk yield on litter weight gain accounted for a moderate amount of the variation in litter weight gain (r2=.59). Milk components such as percent dry matter and percent ash were not affected by treatment (Table 19). However, each exhibited a time effect with percent dry matter decreasing (Figure 30) and percent ash increasing (Figure 31) as lactation progressed. In addition, percent crude protein and percent lactose were unaffected by treatment and remained relatively constant throughout lactation (Figures 32 and 33). Mean lactation milk fat as a percentage of milk was not different between treatments, however, there was a treatment x time interaction (P<.05) with SA sows maintaining fat levels at d21 and d28 of lactation (Figure 34). The trend between day 21 and 28 for SA versus NC and CC sows was significantly altered (p<.05). Gross energy values for milk samples did not differ significantly for NC compared to CC sows. However, SA sows showed a lower mean value at day 14 of lactation as compared to either NC or CC sows. The treatment trends for milk gross energy were not statistically different from day 14 to day 28 for SA versus NC and CC sows (Figure 35). Overall treatment means and weekly treatment means are listed in Table 20. Blood levels of insulin and glucose were not different between treatments and across time (Table 21 and Figures 36 and 37). Blood urea nitrogen levels were higher on day 28 (p<.05) for NC sows as compared to SA sows. In addition, mean trends were different for SA versus NC sows from days 7 128 WEEK Figure 30. Mean Milk Dry Matter of NC, CC and SA Sows Measured Weekly in Lactation. ASH, X Figure 31. Mean Milk Ash of NC, CC and SA Sows Measured Weekly in Lactation. Figure Figure 33. Mean Milk 129 * \ g -—-""--;' I 8 "O"".0 a... C " '0' G. .,0’ III '0'.' o ,..o a , ------- c a. ......... ° 5.2 ~ 0" —.- an --o-- cc ‘—o- us 5"1 2 a 4 WEEK 32. Mean Milk Crude Protein of NC, CC and SA Sows Measured Weekly in Lactation. 5.3 315.2 LACTOS E, WEEK Lactose of NC, Weekly in Lactation. CC and SA Sows Measured 130 LIPIDS, X WEEK Figure 34. Mean Milk Lipids of NC, CC and SA Sows Measured Weekly in Lactation. 1180 -1— n: --o-- cc 1100 1140 Kcsl I kg 1120 1100 1080 1 WEEK Figure 35. Mean Milk Gross Energy of NC, CC and SA Sows Measured Weekly in Lactation. 131 Table 20. Effect of Feeding Level and Stage of Lactation on Milk Yield and Milk Composition. Milk Dry Ash, Milk Crude Lactose GE Yield Matter X Fat Protein X kcal/kg NC 6.7 18.9 .71 7.72 5.36 5.05 1159 d 7 CC 7.3 18.9 .73 7.61 5.42 5.13 1164 SA 7.4 18.9 .73 7.84 5.36 5.10 1135 NC 8.0b 18.6 .78 7.61 5.44 5.03 1142 d 14 CC 8.2b 18.6 .74 7.20 5.12 5.22 1137 SA 9.0c 18.4 .75 7.41 5.27 5.11 1110 NC 8.2b 18.7 .80 7.41 5.45 5.08 1132 d 21 CC 8.7bc 18.3 .78 7.12 5.18 5.19 1133 SA 8.90 17.9 .79 7.41 5.29 5.14 1118 NC 8.1b 18.4 .81 6.86b 5.38 5.20 1085 d 28 CC 8.3be 17.9 .83 6.81b 5.42 5.08 1098 SA 8.8c 18.0 .82 7.51c 5.32 5.18 1120 SEM‘ .92 1.01 .14 .25 .71 .69 66.3 ‘ Pooled standard error of the mean. b. c Means with different superscripts differ (p<.05). Table 21. Concentration of Insulin and Selected Metabolites in Blood During Lactation. Hormone or Insulin Glucose Blood Urea NEFA Metabolite (mg/ml) (mg/ml) Nitrogen (mg/d1) (meq/l) NC .87 68.2 43.9 171.2 wk 1 CC .80 72 38.0 200.1 SA .75 72 38.0 180.7 NC .81 66.6 39.7 199.2b wk 2 CC .74 68.7 36.2 209.8b SA .76 73.8 40.4 166.9c NC .84 67.3 40.7 200.3b wk 3 CC .76 71.4 37.9 184.9b SA .79 71.5 39.4 162.2c NC .81 65.2 45.8b 193.1b wk 4 CC .70 68.1 38.7be 189.6b SA .79 72.1 37.9c 154.2c SEM‘ .21 3.3 3.1 14.7 ‘ Pooled standard error of the mean. b. c Means with different superscripts differ (p<.05). 133 Figure 36. Mean Serum Insulin Concentrations of NC, CC and SA Sows Measured Weekly in Lactation. Figure 37. Mean Plasma Glucose Concentrations of NC, CC and SA Sows Measured Weekly in Lactation. 134 to 14 and days 21 to 28 (Figure 38). Blood nonesterified fatty acids (NEFA) levels were not significantly different for NC and CC sows. NEFA levels were significantly lower (p<.05) of SA sows as compared to the NC and CC sows on days 14, 21 and 28 (Table 21) of lactation (Figure 39). Measurement of feed intake for sows used in the energy and nitrogen balance study, indicated NC sows consumed less feed and thus less gross energy (GE) than SA sows in both the d 8-13 and d 22-27 periods (p<.05) (Table 22). In addition, the NC and SA sows consumed more feed in d 22-27 period then the d 8-13 period (p<.05). Feed intake for CC sows was not different between test periods (p>.10). Daily fecal output and fecal GE were significantly less for NC sows as compared to both CC and SA sows (p<.04), however, no differences were detected between means of CC and SA sows. No time differences were seen in fecal output or fecal GE for treatments. No differences were observed in treatment or time for daily urine output or urine gross energy. Digestible energy (DE) and metabolizable energy (ME) intake was greater (p<.05) for both CC and SA sows as compared to the NC group in the d 8-13 period. DE and ME intake were greater for SA sows versus both NC and CC in the d 22-27 period (p<.05). No differences were observed in DE and ME intake for the d 8-13 period between SA and CC sows. In addition, no mean difference was seen in the d 22-27 period between NC and CC sows. There was a time effect on DE and ME intake for NC and SA sows (p<.05), but no difference was 135 WEEK Figure 38. Mean Blood Urea Nitrogen Concentrations of NC, CC and SA Sows Measured Weekly in Lactation. IanL WEEK Figure 39. Mean Blood Non-esterified Fatty Acid Concentrat ions of NC , CC and SA Sows Measured Weekly in Lactation. 136 Table 22. Energy and Nitrogen Balance of Sows in Early or Late Lactation. Stage of Lact. d 8-13 d 22-27 Treatment NC CC SA NC CC SA SEM No. of Obs 4 4 4 4 4 4 Feed Intake kg/d 5.2" 6.7be 7.0be 6.3Ml 6.8‘5c 9.2bd .14 GE Intake, Mcal/d 23.0. 29.7 31.0be 27.9‘ 30.1‘” 40.7bd .11 DE Intake, Meal/d 17.6‘° 22.0c 23.0be 21.7" 22.5‘‘3 30.3bd .13 Fecal dry, wt, kg/d 1.87‘ 2.22b 2.37b 1.56‘ 2.22b 2.57b .41 Fecal GE, Mcal/d 5.4‘ 7.7b 8.0b 6.2‘ 7.6b 10.4b .47 Urine, kg/d 4.8 5.6 6.3 5.5 5.8 6.5 .27 Urine GE, Mcal/d .53 .61 .66 .50 .62 .71 .42 ME, Mcal/d 17.1:c 21.4be 22.3bc 21.2“d 21.9-c 29.6bd .14 N-balance, g/d -30.5‘c -35.9'° -18.3bc -16.0'd «19.0‘d 4.4bd .42 N-corrected ME, Mcal/d 17.3“c 21.6be 22.4bc 21.3" 22.0"c 29.6bd .15 ME/GE, X 75.2 72.7 72.2 76.3 73.1 72.3 .19 Lact Energy (LE). Mcal/d 8.54c 8.9bc 9.1bc 9.0‘d 9.5“l 9.9M .61 Est. Diet. Energy Req. LE, Mcal/d 13.1‘c 13.7be 14.0bc 13.8‘9 14.6.cl 15.2bd .52 Est. Maint. Req. Meal/d 6.2 6.2 6.1 6.1 6.1 6.2 .09 Est. Energy Bal. Mcal/d -2.2‘¢ 1.5be 2.2be 1.3“ 1.2‘° 8.2M .13 ‘:5 Means with different superscripts differ (p<.05).Treatment effect. c-d Means with different superscripts differ (p<.05). Period effect. 137 seen in the CC group of sows. Nitrogen balance was not different for the NC and CC sows (p>.10) but was significantly reduced for the SA sows in both time periods (p<.02). The negative nitrogen balance was significantly reduced for all treatments as lactation progressed (p<.05). Nitrogen corrected ME intake was greater for CC and SA versus NC sows in the D 8-13 period and was increased for SA versus NC and CC (p<.05) and not different for NC verses CC sows in the d 22-27 period. Nitrogen corrected ME intake was greater for NC and SA sows in the d 22-27 period as compared to the d 8-13 period (p<.05). Period in lactation did not affect nitrogen corrected ME intake in CC sows. Efficiency of energy utilization as measured by ME/GE tended to be greater for NC sows in both collection periods (p<.08). D' . Gastric cannulation of sows provides a way to achieve feed intake in excess of ad libitum levels for sows during lactation. SA sows had feed intake levels significantly greater than both NC and CC sows particularly in weeks 3 and 4 of lactation. Calculated intake levels for' CC sows approximated intake levels of ad libitum fed NC sows. The overall performance of NC versus CC sows shows the cannulated sows can perform as well as or superior to non- cannulated counterparts. Litter size at weaning and litter weights were not different for NC and CC sows thus showing 138 that the cannulation process did not impair lactation performance. As lactation feed intake levels were increased, due to increased alimentation, sow weight and backfat loss during lactation were reduced. These results are similar to those reported by Reese, et al., (1982, 1984), King and Williams (1984 ab), O’Grady, et al (1985) and Kirkwood et al. (1987). The ‘weight and backfat gain, as seen in the SA sows, indicate that nutrients fed in excess of ad libitum to a large degree are digested and absorbed. The increased level of nutrients appear to have provided increased substrate for additional milk yield and litter weight gain as well as body weight and backfat gain in lactating sows. Restricted energy resulted in reduced milk yield and litter weight gain and. an increase in sow' body weight and back fat loss (Verstegen et al., 1985; Noblet and Etienne, 1986). Weight gain has been reported in lactating sows where litter size and milk yield are small (Whittemore, 1987). However, in most instances where high production levels are attained, sow weight loss in lactation is assumed (ARC, 1981; Close and Cole, 1986). As a result of spontaneous energy restriction, sows will not maximize lactation productivity and, if the limitation is severe, perhaps sow longevity will be affected as well (Kirkwood, 1988). Milk yield, as measured by the weigh-suckle-weigh method has been used extensively and is reasonably accurate (Lewis et al., 1984). In this study, no attempt was made to 139 estimate evaporative losses or metabolic losses due to activity level (Noblet and Etienne, 1986). The correlation for litter weight gain and milk yield was positive and significant (p<.01, r=.78). Milk yield, as measured in this study, did peak during d14-21 period. Overall milk yield is somewhat higher than reported by others (Speer and Cox, 1984; Verstegen et al., 1985; Noblet and Etienne, 1986). This difference in the present study is due, in part, to larger litters and selection for sow miling ability. Concentration of milk constituents were relatively unaffected by lactation feed intake. Normal variation in milk components was observed similar to Noblet and Etienne (1986) and den Hartog et al. (1987). Percent dry matter tended to decrease slightly as lactation progressed (Brent, 1973; den Hartog et al., 1987). As dry matter decreased, however, percent ash increased slightly, which. also was observed by Brent, (1973) and den Hartog et al. (1987). One milk constituent affected by treatment was percent milk fat. As lactation progressed to the third and fourth week, milk fat concentration decreased in NC and CC sows as previous research has indicated (Brent, 1973; Klaver et al. 1981; den Hartog et al. 1987). However, in the SA sows, as body weight and body fat increased, milk fat was maintained at a constant level through d 28 of lactation. As a result, milk gross energy was maintained through. the fourth.‘week of lactation also. With greater nutrient availability for milk synthesis, due to superalimentation, milk fat levels in SA 140 sows were maintained in late lactation as compared to both NC and CC sow groups. This indicates that the excess nutrients are being digested and absorbed. These nutrients were used in body weight and body fat gain as well as increased milk synthesis and excretion. Blood levels of insulin and glucose were not different for treatment groups or over time. The number of observations may have been inadequate to detect small differences. These findings differ somewhat from those of previous work which showed that sows restricted in feeding level showed a decrease in both glucose and insulin levels (Ruiz et al., 1971; Armstrong et al., 1986). Even though NC and CC sows were in a negative energy balance the severity was not great and therefore a depression in blood glucose and insulin may not have been affected. BUN levels were slightly higher for both NC and CC sows as compared to SA sows. This is a result of negative nitrogen balance and is consistent with the literature (Brendemuhl et al., 1987). NEFA levels were observed to be somewhat higher for NC and CC versus SA sows. Again, these results reflect energy balance differences. As energy balance becomes negative, breakdown of fat tissue begins. This results in an increase in blood NEFA levels for sows in a catabolic state (Brendemuhl et al., 1987). Energy and nitrogen balance work was accomplished by measuring feed intake and collecting and measuring urine and fecal output of sows. The increase in urine output by CC 141 and SA versus NC sows may be partly due to increased water intake. Feed was administered to sows via a slurry in a weight ratio of 4 parts water to 3 parts feed. This would result in 9 kg water intake in the CC sows and 11 kg water intake for SA sows per day. These sows had free access to water via an automatic nipple waterer. Normal water intake for lactating sows may be as high as 20-25 kg per day (NRC, 1988). Fecal dry matter output was greater for SA sows. This is understandable since these sows had greater total dry matter intake. Efficiency of feed utilization appeared to be slightly improved for NC sows. This may result from several factors. The cannulation process may have slightly impaired digestive processes, although this is unlikely. Generally, a slight restriction in feeding level of grower pigs results in a small improvement in digestibility and growth efficiency (Kanis, 1988). Thus, as feeding level increases, overall digestibility efficiency of nutrients decreases slightly, but the total amount of nutrients absorbed increases dramatically. This appears to explain the small reduction seen in efficiency of energy utilization. Lactation energy (LE) is mean milk yield multiplied by mean milk gross energy as measured at the beginning and end of each collection period. The estimated energy requirement for lactation energy assumes (65X efficiency for conversion of feed energy to milk energy (ARC, 1981; Verstegen et al., 1985; NRC, 1988). SA sows had 142 greater LE production and therefore greater feed requirements than NC sows in the d8-13 period (p<.05). SA sows had greater LE production and LE requirements than both NC and CC sows in the D22-27 period (p<.05). LE energy and LE requirements did increase from d8-13 to d22-27 period for all treatments. Estimated maintenance requirements were not different for treatment groups or for stage of lactation. Estimated Energy balance was significantly lower for NC sows as compared to CC and SA sows in the d8-13 period. NC and CC sows d22-27 period. NC and SA sows increase in estimated energy balance from d8-13 period to d22-27 while CC sows were not different between periods. Estimates are based on previous studies of Verstegen et al. (1985) and Noblet and Etienne (1986) for energy balance in lactating sows. Conclusions Feeding of lactating sows via gastric cannulae can be accomplished without adverse effects on sow productivity or piglet performance when performed in cool weather. Nutrient digestion and absorption in lactating sows fed in excess of ad libitum is not restricted, as seen, by sow and litter performance. Increasing feed intake level beyond ad libitum levels resulted in increase in sow body weight and backfat. Milk yield and litter weight gain is also increased as a result of increased feeding levels to sows. Milk composition is not greatly affected by superalimentation of sows in lactation, but yield of milk constituents was 143 enhanced. Fat levels in milk tend to remain constant through lactation as compared to a normal decrease in milk fat level for ad libitum fed sows. Sows in a positive energy and nitrogen balance have lower blood urea nitrogen levels and lower non-esterified fatty acid levels. Sows fed above ad libitum levels tend to digest and absorb nutrients slightly less efficiently than ad libitum fed sows that are in a negative nitrogen and energy balance. In this study, sow lactation performance is increased as a result of increased. nutrient availability. Thus, spontaneous feed intake in the lactating sow, limits overall sow lactation performance. GENERAL DISCUSSION In lactating sows many factors control voluntary intake of feed. Continuing efforts to maintain or improve profitability of pork enterprises have resulted in improved understanding of sow lactation feed intake and lactation performance. Further study of physiological control of feed intake and feeding activity has resulted in additional knowledge and understanding. Nevertheless, the ability to use this knowledge to aid in describing or predicting sow lactation feed intake is limited. O’Grady et al. (1985) and NRC (1987) describe prediction equations for lactating sows using limited factors associated with daily feed intake. O’Grady et al. (1985) could only account for 24-29X of the variation in daily lactation feed intake. However, feed intake in sows was limited. to feed consumed.‘within 45 minutes after feeding. Therefore, consumption of feed was limited thus reducing prediction capabilities. Researchers have shown effects of various environmental factors on daily lactation feed intake. Lynch (1977) showed reductions (12X) in sow lactation feed intake when ambient temperature was increased from 21'C to 27°C. When Experiment I data were divided into sow lactation groups exposed to different temperature levels, a reduction of 20X 144 145 in feed intake for sows exposed to >26'C versus <22'C daily high temperature occurred. A larger decrease of 23X was seen for sow groups exposed >25'C versus <21'C daily low temperature in lactation. Sows exposed to very warm daily high temperature in lactation (>27'C) with daily low temperature of either >24°C or <24'C showed a significantly different response in mean daily lactation feed intake. Those lactating sows maintained in a warm environment (>24°C) consumed 16X less feed than sows exposed to cooler temperatures (<24'C). Although sows were exposed to hot daily high temperatures (<27'C), the response of sows to cooling (<24'C) for part of the day resulted in a dramatic improvement in lactation feed intake. Season of the year has been shown to affect changes in sow lactation feed intake. Mean daily high temperatures for March-May farrowed sows was 22.1'C; September-November farrowed sows was 22.6'C; December-February was 21.2'C; June August was 26.7'C. Feed intake were basically unaffected during the cool months of the year which also was seen by O’Grady et al., (1985) and Britt, (1986). However, as seen by these two researchers, feed intake reduction was very evident in the warmer months of the year. Britt (1986) showed a reduction in feed intake into September and October, however, these data were gathered in a geographically warmer climate. In all cases where temperature was used as a segregating criterion, there was a treatment by time interaction. This indicated that sow 146 groups exposed to different temperature levels were reaching peak feed intake at different rates. When temperature was used as a covariate the degree of significance for season was reduced. But, season continued to be a significant factor in feed intake of lactating sows. Backfat depth of sows at farrowing has been reported to influence lactation feed intake (Lodge et al. 1972; Cole, 1982; Aherne and Kirkwood, 1985). In general, sows with greater body fat stores tend to consume less feed in lactation (Cole, 1982; O’Grady et al. 1985). In the current study, a reduction of at least 0.2 kg daily lactation feed intake for every 3 mm additional sow backfat greater than 11 mm up to >21mm was observed. MacLean (1968, 1969), Reese et al. (1982), King and Dunkin (1986A) and Johnston (1988) observed a greater incidence in cessation of ovarian function in sows that were thin due to reduced or limited lactation feed intake. Therefore, a balance between body energy stores and maximum lactation feed intake must be utilized to achieve optimum sow longevity and reproductive performance. But, standards for minimum body fat levels have not been established. Lactation feed intake was correlated positively with sow body weight at farrowing (P=.18). However, feed intake between weight classes of lactating sows was not significantly different in this study, but tended to be greatest and heavier sows. There was a trend toward greater feed intake as sow weight was elevated. Parity and sow 147 weight were correlated positively (P=.59). There was a significant difference in feed intake of parity classes. As parity increased mean daily feed intake increased. These findings are similar to previous reports (Mahan, 1977, 1989; O’grady, et al., 1985; Britt, 1986). Therefore, in general, feed intake tends to increase with body weight and parity. Numbers of pigs weaned affected mean daily feed intake of sows in lactation (Elsley, 1971; O’Grady et al., 1985). Increasing litter size from 8 to 10 pigs weaned resulted in 7.5% increase in daily feed intake of lactating sows. Increasing litter size from <7 to >11, resulted in a 31X increase in sow mean daily feed intake in lactation. For every pig over 7 pigs per litter, a 0.2 kg increase in daily lactation feed intake should be expected. Sow milk yield and litter weight at day 21 of lactation were correlated positively (P=.66). As previously reported, milk yield is positively correlated with suckling intensity (Elsely, 1971; NRC, 1981; O’Grady et al., 1985). An increase in 21 day litter weight from <39 kg to >57 kg resulted in a mean daily increase in sow lactation feed intake of 41X. If moderately productive sows (48-56 kg 21 day litter weight) are compared to moderately low producing sows (39-47 kg 21 day litter weight) a 10% difference in mean daily lactation feed intake was observed. Therefore, litter size and sow milking ability have a large impact on daily sow lactation feed intake. If the sow’s milking ability is superior an 148 additional 10-20X increase in daily feed intake should be expected. Stage of lactation affects daily feed intake of sows. Mean daily feed intake levels of 4.0, 5.5, 5.8 and 6.1 kg for weeks 1 to 4 of lactation, respectively, were significantly’ different. Thus, as lactation. progressed, daily feed intake increased until d28 of lactation. This is similar to reports by Stahly et al. (1976) and O’Grady et al. (1985). Sow rectal temperature at farrowing reduced feed intake during the first week of lactation. Thus, sow health is important in maintaining feed intake, milk production, piglet survivability and growth rate during the first stage of lactation (Elmore and Martin, 1986). To better understand lactation feed intake on a daily basis, sows were divided into response groups on the basis of total lactation feed intake. Sows with low feed intake showed a delay in reaching near maximum feeding levels, as seen in week one of lactation. In addition, low intake sows never reach the daily intake level of high intake sows in the later stages of lactation. As a result of low feed intake levels, these sows lost more weight and body fat than did their counterparts consuming large amounts of feed (Verstegen, et al., 1985; Noblet and Ettienne, 1986). The surgical technique developed to place gastric cannulae in gestating sows does not appear to negatively affect sow or litter performance. Mean litter size, number 149 of still births and mummified fetuses were unaffected by the surgical procedure. In addition, gastric function did not appear to be altered as feed intake during gestation and subsequent lactation performance were not impaired. Feeding cannulated sows in excess of ad libitum increase feed intake, and therefore greater metabolizable energy intake. Sows fed ad libitum or cannulated sows fed at NRC (1988) recommended levels lost weight and backfat in lactation. Sows that were superalimentated gained weight and increased backfat depth in lactation. In addition, superalimentated sows yielded larger quantities of milk and heavier litters at day 21 of lactation. Concentration of milk constituents were not affected due to treatment. However, milk lipids did not decline in the latter stages of lactation for superalimentated sows as compared to control treatments. In addition, as a result of maintaining milk lipids at a higher level in weeks 3 and 4 of lactation, superalimentated sows tended to maintain higher levels of gross energy in milk as compared to the control treatments. Blood glucose and insulin concentrations at base line levels were unaffected by treatment. Blood levels of urea nitrogen and non-esterified fatty acids tended to be lower for superalimentated sows as compared to control treatments. In addition, superalimentated sows displayed a positive energy and nitrogen balance for the latter stage of lactation as compared to a negative balance situation for the control treatments. A negative nitrogen and energy 150 balance will usually exist for sows fed ad libitum with production levels similar to sows in this study (Brendemuhl et al., 1987; Whittemore, 1987). Efficiency of energy absorption were numerically greater but not significantly different for sows consuming less feed in lactation as compared to superalimentated sows. However, lactation performance, due to increased nutrient intake was superior for the superalimentated sows. This indicates findings similar to Pekas, (1985). Digestion and absorption of nutrients are not the limiting factors in sows lactation performance. IHowever, limitations, whether they are physical of physiological, on sow lactation feed intake limit sow lactation response. Therefore, management practices to enhance lactation feed intake should be implemented. Furthermore, a clearer understanding of physiological limitations on meal size and meal frequency need to be elucidated. SummarLand_Conolusions Daily feed intake of lactating sows is affected by many factors. Those factors that were most influential were ambient temperature, sow backfat at farrowing, litter size, sows milking ability, parity and day of lactation. In predicting daily lactation feed intake only 38X. of the variation can be described using the variables listed above. 151 Gastric cannulation of pregnant sows can be accomplished without affect on farrowing or lactation performance. Sows fed in excess of ad libitum had increased body weight, greater backfat thickness, greater milk yield and litter weights than controls with greater milk yield and similar milk composition, total yield of milk components was increased. Sows fed in. excess of ad libitum tend to maintain higher levels of milk lipids throughout lactation. Superalimentated sows fed at a 29 Mcal ME level were in positive energy and nitrogen balance. Therefore, digestion and absorption of nutrients are not the limiting factor in determining lactating sows performance. IExtra. nutrients were utilized by lactating sows to increase body nutrient stores and by sow mammary tissue for increased milk yield. 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