‘5 ti») LlBthh. 3, g IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIl 10459 4423 M 1» Us-» .-.--; This is to certify that the thesis entitled Rumen By-Pass of Protein Through Esophageal Groove Closure in Lactating Cows presented by Frank E. Standaert has been accepted towards fulfillment of the requirements for M.S. degree in Dairy Science Date 3/4/?9 / / / 0-7 639 «ogN OVERDUE FINES ARE 25¢ PER DAY PER ITEM «a; was .\ ,I‘ \’ Return to Book drop to remove this checkout from your record. RUMEN BY-PASS OF PROTEIN THROUGH ESOPHAGEAL GROOVE CLOSURE IN LACTATING COWS BY Frank E. Standaert A THESIS Submitted to Michigan State University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE Department of Dairy Science 1979 x... v. .3..\\ h. ABSTRACT RUMBN BY-PASS OF PROTEIN THROUGH ESOPHAGEAL GROOVE CLOSURE IN LACTATING COWS BY Frank E. Standaert Nineteen Holstein heifers, (22-23 mo), were trained in two trials to suckle fluids from a nipple pail. In both trials, animals were forced fed fluids daily through a nipple pail after a 10-12 h withdrawal from water. As animals began actively suckling, water was gradually re- introduced until free choice. Training periods lasted 2-3 weeks after which most animals would suckle. Several single crossover design trials with two 1-day periods were used to determine rumen by-pass. Blood glucose tolerance curves were compared for animals that suckled a 500g glucose solu- tion to those which received 500g glucose directly in the rumen. In all trials, mean serum glucose levels at 1 and 2 hours after glucose load was greater (P<.05) for the suckled animals, though a few heifers showed no rise in blood glucose after suckling. Six animals which maintained the suckling habit were used in a single cross over experiment to deter- mine the effect of suckling milk on milk and milk protein production. The suckled group was offered sufficient whole milk to furnish 500g milk protein daily but mean intake was Frank E. Standaert only 320g. Control animals received 500g casein daily in the concentrate. Periods lasted 3 weeks. All animals were fed a corn silage-haylage mix ad libitum and 1 kg of 12% protein concentrate for every 3 kg milk produced. Milk yields, milk protein percent and protein yields for the suckled and control groups were: 22.2 kg, 21.2 kg; 3.64%, 3.51% (P<.l); 808g, 735g (P<.05). The suckled and control groups consumed 92% and 103.8% of NRC requirements for protein. ACKNOWLEDGEMENTS The author extends his sincere gratitude and apprecia- tion to the members of the committee for their guidance throughout this research study. Drs. John T. Huber and Roy S. Emery were very helpful with working with the animals and their encouragement and suggestions. Dr. Werner G. Bergen gave valuable insight during the course of the experiments and in interpreting data. The author also expresses deepest thanks to his fellow graduate students who may have helped in a great variety of ways. Help with training, feeding and daily care of the animals is sincerely appreciated. Also, the stimulating discussions with fellow graduate students was a very valuable portion of this author's graduate study. ii TABLE OF CONTENTS Page LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . iv LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . vi INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . LITERATURE REVIEW . . . . . . . . . . . . . . . . . . . Rmnen By-pass o o o o o o o o o o o o o o o o o o o Abomasal Infusion Studies in Lactating Cows . . . . Methods Used to Facilitate Rumen By-pass of Protein Heat treatment of proteins . . . . . Chemical treatment of proteins . . . Antibiotics . . . . . . . . . . . . Esophageal groove closure . . . OGDVU'IUI (N H ....:11 Research Preposal . . . . . . . . . . . . . . . . . 14 MATERIALS AND METHODS O O O O O O O 0 O O O O O O O O O 1 5 Animals and Management . . . . . . . . . . . . . . 15 Training Trial I . . . . . . . . . . . . . . . . . 15 Rumen By-pass Determination . . . . . . . . . . . . 16 Training Trial II . . . . . . . . . . . . . . . . . 17 Production Trial . . . . . . . . . . . . . . . . . 17 Final Rumen By-pass Trial . . . . . . . . . . . . . 21 Handling and Processing of Samples . . . . . . . . 21 Statistics . . . . . . . . . . . . . . . . . . . . 24 RESULTS AIVD DISCUSSION 0 O O O O O O O O O O O O O O O O 26 Training Trial . . . . . . . . . . . . . . . . . . 26 Rumen By-pass Determination . . . . . . . . . . . . 29 PIOdUCtion Trial 0 O O I O O O I O O O O O O O O O 40 Conclusions . . . . . . . . . . . . . . . . . . . . 51 BIBLIOGRAPHY O O O O 0 O O O O O O O O O O O O O O O O O 53 APPENDIX 0 O O O O O O O O O O O O O O O O O O O O O O O 61 Table 10 11 12 LIST OF TABLES Rumen by-pass determination trials, solu- tions used, method of control, time and method of sampling Ingredient composition of concentrate used throughout the experiment Schedule of treatments for final by-pass trial Sources of variation and degrees of free- dom for model used in production trial Results of training trials. Number of animals suckling successfully at several times after beginning of training Mean serum glucose levels (mg/100 ml) for all animals in the 4 by-pass trials Mean serum glucose levels (mg/100 ml) for only animals obtaining rumen by-pass Difference in mean serum glucose (mg/100 ml) two hours after administration of treatment Mean serum glucose levels (mg/100 ml) two hours after ingestion of 500g glucose for animals in production trial Dry matter content and concentration of nutrients in the dry matter of feedstuffs used in the production trial Effect of suckled whole milk on DM intake, supplement intake, total protein intake and NE1 intake Whole milk protein consum tion through nipple pails for each cow on pro uction trial iv Page 18 20 22 25 27 30 36 37 41 42 44 Table 13 14 15 Effect of suckled whole milk on yield of milk, milk fat and milk protein, milk fat percent and milk protein percent Total protein (kg/day) available at the abomasal level for cows in this study Effect of suckling whole milk on mean serum levels of urea-N and glucose Page 45 SO 52 Figure LIST OF FIGURES Serum glucose response to glucose either suckled or placed directly into the rumen for all animals in by-pass trials Serum glucose response to glucose for animal obtaining rumen by-pass Serum glucose reSponse to glucose for animal not obtaining rumen by-pass Serum glucose reSponse to glucose either suckled or placed directly into the rumen for only animals obtaining by-pass Serum glucose response to glucose for animals in production trial Effect of suckling milk protein on increase in milk protein yield vi Page 31 32 33 34 39 48 INTRODUCTION Efficiency of use of nutrients by animals is determined by two basic factors. The digestive system of the animal and the composition and quality of the feedstuffs containing the nutrients. For ruminant nutritionists, the presence of the rumen presents the first major obstacle in the efficient use of quality feeds. High quality proteins are almost completely degraded in the rumen to yield lower quality microbial protein in lesser quantities than the protein originally added. Because the nonruminants do not have a pre-gastric microbial fermentation, the full benefit of a high qualtiy protein source can be appreciated. At the same time, the presence of the rumen enables the ruminant to utilize a more diverse selection of lower quality and high fiber feeds. The ruminant can convert low quality proteins, NPN and roughages into higher quality microbial protein for productive function. To increase productivity then, either the capacity to produce microbial protein must be increased or methods by which high quality protein can pass through the rumen undergraded must be employed. ESOphageal groove closure is the natural means in young rumi- nants by which milk "by-passes" the undeveloped rumen and enters the abomasum for efficient digestion and absorption. This reflex closure of the groove, if operable in the adult cow, may present one way in which nutrients could escape the inefficient fermentation in the rumen and be utilized to a greater extent by the animal. The object of this investigation is to determine whether esophageal groove closure cows and if it can be used to feed the dairy cow a portion of the nutrients required for lacta- tion. LITERATURE REVIEW Rumen ByjPass The beneficial effects of by-passing the rumen with protein have been observed for some time. Many of these effects were seen in experiments comparing the protein quality of different feed sources for ruminants. Chalmers and Synge (1954) correlated the greater value of herring meal supplements over casein supplements for sheep with the lower evolution of ammonia in the rumen from the herring meal. A greater proportion of the herring meal supplement passed through the rumen undegraded and resulted in better wool growth and increased nitrogen retention. Earlier, Cuthbertson and Chalmers (1950) had shown that casein had little value as a protein supplement for sheep unless the rumen was by-passed. The rapid deamination of this high quality protein has a “detrimental effect on its utilization. These workers showed an increase in nitrogen retention when casein was administered into the duodenum of sheep. They also showed that this increase diminished as the basal intake of nitrogen increased from 6g to 25g per day. No difference in nitrOgen retention was obtained at the high level of nitrogen intake (Chalmers et a1. 1954). The solubility of different protein sources in rumen liquor was found to be a major factor influencing the degree 3 4 of by-pass. McDonald (1952) showed that dietary proteins soluble in the rumen fluid were rapidly fermented. Fontaine et al. (1944) reported better utilization of the nitrogen in ground nut meals when the percentage of salt-peptizability or solubility of the protein is low. Solubility, however, is not the only important factor involved in nitrogen utiliza- tion. El-Shazly (1958) showed that casein gave better nitro- gen retention than meat meal and beans, both of which are less soluble and generate lower rumen ammonia concentrations. Chalmers (1961) pointed out that the nitrogen digestibility of these protein sources has a controlling effect on the nitrogen retention observed. She reported that the digesti- bility of nitrOgen for meat meal, beans and casein were 47, 59 and 70 percent and nitrogen balance decreased as nitrogen digestibility decreased, concluding the ideal ration for max- imum use of nitrogen should contain protein of good digesti- bility with a low solubility in rumen fluid. When casein was heated or denatured into hard lumps and then ground, the solubility in rumen fluid decreased and the nitrogen balance increased (Chalmer et a1. 1954). The results of these and other studies were a major impetus for extensive research in two areas of protein nutri- tion over the last 15 years. IOne line of work investigated the various methods by which protein could be protected from degradation in the rumen and still be well-digested in the intestine, the other studied more extensively the overall effects of rumen by-pass of nutrients utilizing the abomasal and duodenal cannulae. Abomasal Infusion Studies in Lactating Cows —4 Because casein is the major milk protein and should pro- vide an ideal mixture of amino acids for milk protein syn- thesis, it has been the protein source used most often in postruminal infusion studies. Also, there is some difficulty in getting plant and other animal proteins into solution or a suitable suspension. Glucose and amino acids have also been used widely for infusion studies. Clark (1975) recently published an excellent review of the postruminal infusion studies in lactating cows. He reported an increase in milk yield of 1 to 4 kg per cow per day when casein was supplemented postruminally. The response in milk yield was accompanied by a 10-15% increase in milk protein yield. Various factors affect these responses although they are not all clearly understood. Level of pro- duction exerts some effect. Greatest increases in milk yield after postruminal protein infusion is from high producing cows. Cows producing over 20 kg milk per day had increase greater than 1 kg of milk per cow per day when casein was infused postruminally. When production was less than 20 kg, increases greater than 1 kg per cow per day were seldom seen. Clark (1975) believes that cows producing in excess of 30 kg milk per day fail to produce to their genetic potential because of the lack of some key nutrient or nutrients. Estimates of rumen microbial protein yields in high produc- ing cows support this concept (Hagan and Weston 1970; Bur- roughs et a1. 1975; Hume et a1. 1970; Ibrahim and Ingalls, 1972). 6 Hale and Jacobsen (1972) infused casein, gelatin, par- tially delactosed whey and zein into the abomasum and found no response in milk yield, however, the cows in this study averaged only 6 kg milk per day. Vik-Mo, Emery and Hubes (1974) observed negative responses in milk yield with cows produc- ing less than 20 kg milk per day. Fluctuations in feed in- take may have contributed to the negative response although energy and protein intake were usually above standard allow- ances. Broderick et al. (1970) reported a significant depression in concentrate intake when 800g of methionine- supplemented casein was infused into the abomasum. Mest workers (Clark, Spires and Derrig, 1973; Derrig, Clark and Davis, 1974; Hale and Jacobsen, 1972; Hale, Jacobsen and Hemken, 1972; Vik-Mo, Emery and Huber, 1974) observed no effect on feed intake when 300-600g of casein was infused into the abomasum. Others (Grskove, Fraser and Pirie, 1973; Papas, Hatfield and Owens, 1974; Spechter, 1972) have reported an increase in feed intake when protein was fed to by-pass the rumen. Clark (1975) suggested the optimum quantity of infused casein for increasing milk production appears to be from 300-500g per day. Infusion of greater quantities has not further increased milk yield. Even for cows fed above NRC standards for energy and protein, infusion of 300-500g casein into the abomasum usually resulted in maximal increases in milk and milk protein yield (Broderick, Kowalczyk and Satter, 1970; Derrig, Clark and Davis, 1974; and Vik-Mo, Emery and Huber, 1974). 7 ¢rskov, Grubb and Kay (1977) studied postruminal infu- sion of casein and glucose with early lactating cows in nega- tive energy balance. These workers observed an increase in milk yield and amount of nitrogen in milk when either casein or glucose was infused postruminally. Vik-Mo et a1. (1974) also showed a response in milk yield to glucose infusion, but less than that of casein, which suggests that energy may be limiting at the mammary gland. In a second experiment, ¢rskov et al. (1977) observed a significant linear and quad- ratic increase in milk yield and yield of nitrogen when levels of casein infused increased from 0 to 750g per day. Casein infusion also doubled the negative energy balance for the cows in this trial as calculated using the equation of Gaines and Overman (1938). These results indicate that cowfilin early lactation and negative energy balance can be limited byran inadequacy of both energy and amino acids for milk protein synthesis. It can be concluded, therefore, that the response in milk yield to protein supplemented postruminally is of a magnitude which might have practical interest. Chalmers (1961), Allison (1970), Hogan and Weston (1970), Smith (1975), and flrskov et al (1977) were all in agreement when they called for the development of a protein rich supplement which escapes ruminal degradation by micro-organisms to a substantial ex- tent and yet remains digestible in the small intestine. Methods Used to Facilitate Rumen By-Pass of Protein Much of the early work on the protection of proteins from ruminal degradation was done at the Prospect Laboratory 8 in Australia and the Rowett Research Institute in Scotland. Reis and Schinkel (1964) demonstrated a biological response that could be used to test the effectiveness of various tech- niques of protection when they noted a marked increase in wool growth of sheep after_abomasa1 infusion of casein or sulfur amino acids. This wool growth response has since been used to evaluate the degree of natural protection of feed- stuffs and test various processing techniques (Reis, 1967, 1970; Reis and Tunks, 1969). Work in this area includes heat treatment of protein, chemical modification of proteins, inhi- bition of proteolytic activity of rumen microbes with anti- biotics and reducing the mean residence time of ingesta in the rumen. Heat Treatment of Proteins zApplication of heat to grains or forages during process- ing can decrease ruminal degradation of protein (Hale, 1973; Schoeman, deWet and Burger, 1972). The reduced rate of micro- bial fermentation has been attributed to the reduced solu- bility of the protein (Tagari, Ascarelli and Bondi, 1962). However, Chalmer et a1. (1954) indicated that grinding of the coarse lumps of insoluble protein may be necessary to enhance rapid passage of the material out of the rumen. Heat processing to obtain protection is at a disadvantage because decreases in digestibility and biological value may also re- sult. The Maillard reaction between sugar aldehyde groups and the free amino groups of protein is responsible for much of the decrease in digestibility (Ferguson, 1975; Chalupa, 1975). This heat damage can also occur in the absence of sugar or oxidizing fat (Bjarnason and Carpenter 1969, 1970). 9 Goering and Waldo (1974) attributed decreased protein diges- tibility and animal performance to heat damage in forages. Some work has been done evaluating the effects of heating time, temperature and moisture on the degree of damage in forages (Goering and VanSoest, 1967). Chalupa (1975) indi- cated that if the_Maillard reaction can be_controlled to de: crease protein solubility in the rumen and yet maintain intes- tinal protein digestibility, animal performance could be increased. This is indeed the case when evaluated by nitro- gen retention, weight gain or feed efficiency (Goering and Waldo, 1974; Hudson, Glimp, Little and Woolfolk, 1970; Sherrod and Tillman, 1962, 1964). Chemical Treatment of Protein Chemical agents which form reversible cross-linkages with amino and amide groups have been studied as a means of protecting proteins. “These linkages decrease the solubility of protein at rumen pH, but are subsequently destroyed in the acidic abomasum making the protein available for digestion by the host animal. Formaldehyde has been studied most exten- sively for its protective ability. The reaction of formal- dehyde with protein has been widely used industrially (Walker, 1964) and has been described in detail (Fraenkel-Conrat and Olcott, 1946, 1948).“A Formaldehyde treatment of casein has resulted in increased nitrOgen retention, wool growth and muscle growth (Barry, 1972, 1973; Faichney, 1971; Faichney and Weston 1971; Hemsley, Reis and Downes 1973; Reis and Tunks, 1969; and Wright, 1971). Treatment of plant proteins 10 feed efficiency have been improved (Chalupa, 1975). Formal- dehyde treatment of forages at ensiling also promotes increases in animal performance (Barry, Fennessy and Duncan, 1972; Brown and Valentine, 1972; Waldo, Keys and Gordon, 1973). Weston (1971) and McRae et a1. (1972) showed that formaldehyde treat- ment of casein decreased total nitrogen digestibility but the amount of non-ammonia nitrogen entering and absorbed in the small intestine was significantly increased. However, work by Schmidt et a1. (1973) and Wachira (1973) indicates for- maldehyde protection of plant proteins will probably affect rumen microbial metabolism, microbial protein production and intestinal digestibility. The use of tennins to protect dietary protein has also been considered. McLeod (1974) suggested that tannins found in seeds and forages may be responsible for some of the natural protection of proteins that is observed. Tannins have been chemically classified as either hydrolysable or con- densed. Zelter et a1. (1970) reported that tannin-protein complexes formed by condensed tannins are not likely to be hydrolysed to yield amino acids in the abomasum. Hydrolys- able tannins, on the other hand, form reversible cross-link- ages with proteins, presumably by hydrogen bonding. These bonds are weakened or reinfgrced by ionic forces (Ferguson, 1975).I Little attention has been given to controlled experi- ments using tannins as a means of protection. It has been shown that bird-resistant sorghum grain having a high tannin content is less readily fermented in the rumen than normal sorghum (Saba, Hale and Theurer, 1972). However, Manson 11 et a1. (1973) showed that this sorghum also has a lower net energy and apparent crude protein digestibility than normal sorghum. Other chemical agents have been investigated but will not be discussed in detail. These include phosphonitrilic halides, polymerized unsaturated carboxylic acids and halo triazines, (Miller 1972), sulfonyl halides and acrolein ace- tals (Miller 1973), hexamethylenetetramine (Schmidt et a1. 1973) and acetylenic esters (Wildi and Miller, 1973). Antibiotics Hogan and Weston (1969) studied several antibiotics in attempting to control rumen protease and deaminase activity. The results were not encouraging and problems with feed in- take were encountered. Schelling et al. (1972) found that 1g per day of oxytetracycline had no overall effect on rumen . metabolism in sheep. When oxytetracycline was given in com- bination with lysine and methionine, these amino acids were increased in the abomasum and plasma. This effect was attri- buted to the presence of oxytetrocycline. However, these workers also experienced problems with depressed feed intake and digestive disturbances. Esthageal Groove Closure Several researchers have given consideration to the eso- phageal groove as a means to obtain rumen by-pass. The clo- sure of the eosphageal groove involves a series of co-ordi- nated reactions of the caudal thoracic esophagus, the reticu- lar groove and the reticulo-omasal orifice (Titchen and New- 12 hook, 1975). These reactions, which are normal functions in young ruminants, facilitate the passage of suckled liquid from the eSOphagus through the reticular groove and omasal canal into the abomasum. This direct passage of suckled liquid into the abomasum is associated with the contraction of the reticular groove. Stimulation of the efferent fibers of the vagus nerve produces grOove contraction and vagal nerve section eliminates it (Comline and Titchen, 1951; Duncan, 1953). ”Factors believed to influence groove closure are age, temperature of the liquid, posture of the animal while suckling and composition of the suckled liquid (¢rskov, 1972). Reik (1954) reported that the presence of sodium salts in the mouth activated groove contraction in calves. Watson and Jarret (1941) also observed groove contraction in sheep using copper salts while MUnning and Quin (1935) used salts of silver and zinc to produce the same effect. Glucose sol- utions also evoked groove closure in cattle, (Titchen, 1968). Wester (1926) stated that the esophageal groove mechanism regressed with age due to a failure of the groove to deve10p proportionately with the rumen and reticulum. Its vagal innervation, he stated, also regressed with age. Two years later, Schalk and Amadon (1928) sucessfully revived the mechanism in an adult cow by re-establishing a liking for drinking milk. After studying groove activity in 15 nor- mally fed cows with rumen fistulae, Schalk and Amadon, (1928) concluded that the groove functions only upon rare occasions in the mature animal. 13 There exists considerable disagreement in the literature concerning the mechanisms of groove closure. Drskov and Benzie (1969) found that the nature of the fluids tested had no influence on the function of the groove. Earlier workers had shown that milk (Wise and Anderson, 1939) and solutions of sodium salts (Wester, 1930; Trautmann and Schmitt, 1933) or cepper sulphate (Watson and Jarrett, 1941) would promote closure of the groove. Qrskov et a1. (1969) and Watson (1944) agree that if lambs are trained to suck from a bottle at wean- ing and do so voluntarily and eagerly, milk would continue to pass to the abomasum for months or years. Wise and Anderson (1939) concluded that with the dairy calf, suckling from a from a nipple pail promoted groove closure while drinking from an Open pail failed to enhance the passage of milk to the abomasum. In a subsequent study, they stated that elevation of the head while suckling had no influence on groove function (Wise et a1. 1942). ¢rskov et a1. (1970) on the other hand, showed that fluids entered the abomasum regardless of whether they were suckled or drunk normally as long as the liquid was consumed as a result of a "pleasurable anticipation" as Opposed to a quenching of thirst. After numerous studies, Qrskov et al. (1970) believe that the groove mechanism is a condi- tional reflex depending on the mood of the animal. They showed that groove contraction occurs even before suckling as a result of anticipation for receiving a suckled meal. Methods by which successful groove closure has been assessed include radiographic observation (Brskov et a1. a1. 1970), visual inspection or palpation through rumen fistulae l4 (Wise and Anderson, 1939), plasma urea nitrogen and feeding of glucose or strontium via nipple bottle and their subse- quent determination in the blood and rumen respectively (Robinson et a1. 1977; Heddie and Ward, 1973; Reik, 1954). Several workers have shown improvement in growth rate and feed efficiency when nutrients by-passed the rumen via closure of the esophageal groove (Grskov, 1972). Guilhermet et a1. (1977) observed improvements in growth and feed effi- ciency with liquid feeding of casein and soya flour to 8 week old calves. However, Robinson et a1. (1976) observed no significant differences in performance of calves fed sup- plemental protein via nipple pail compared to calves fed the same protein included in the basal ration. They also ob- served a trend towards reduced weight gains and dry matter intake with nipple fed calves. If groove closure can be re-initiated in adult ruminants to allow substantial high quality protein to enters the aboma- sum, post-ruminal infusion studies suggest that there would be marked improvement in weight gain, feed efficiency, nitro- gen balance or milk and milk protein production, depending on the animal's productive function. Research PrOposa1: The objectives of this study were: 1. Train lactating cows to suckle fluids from a nipple pai1. 2. Determine whether rumen by-pass of the suckled fluid occurs. 3. Determine the effects of suckling a high quality pro- tein as a portion of the ration on milk and milk protein yield. MATERIALS AND METHODS Animals and Management A total of 19 Holstein-Friesian heifers were used in this study. The animals were approximately 22 months of age at the beginning of the training trials and were due to freshen at about 25 months of age. All heifers were born and raised in the Michigan State University dairy herd. They were housed in a stanchion barn equipped for individual feeding throughout the trial. After freshening, the animals were milked at 0400 and 1500 hours daily. On most days, the cows were turned into a dry lot for 2-3 hours after the morn- ing milking before returning to the stanchion barn. TRAINING TRIAL I: Feed was withheld from 6 heifers in an attempt to initiate a desire for suckling. A nipple bottle containing whole milk was introduced into the animal's mouth the morning and evening of each day during the training per- iod. This "force feeding" procedure required two workers. One would restrain the animal's head and the other worker would direct the nipple into the mouth of the animal. Milk was forced out of the nipple by one worker and the mouth was held tightly shut around the nipple to force swallowing. Approximately 10-20 minutes were spent with each animal dur- ing each attempt. After two days of trying this method, no 15 16 progress had been made towards initiating a desire to suckle. 0n the third day, dry hay was fed ad-libitum and water was witheld for 12-14 hours. The animals were not allowed access to water until about 1 hour after being forced to suckle whole milk. After several days of continued training the animals began to show less anxiety for the nipple and more active suckling. Thereafter, the majority of the animals needed only to be introduced to the nipple bottle and suckling was completed with few problems (see Plate I, Appendix). The animals were allowed to suckle approximately 4 liters of whole milk followed by as much water as they would voluntarily con- sume through the nipple, which ranged from 2-10 after each feeding. After two weeks of training, free choice water gradually re-introduced to animals. Beginning with the third week of training, heifers were fed by nipple only in the morn- ings so as to maintain the suckling habit. Rumen By-pass Determination Before the heifers freshened, three trials were con- ducted to determine if rumen by-pass was occurring. A two- period changeover design with two treatments was employed. Four liters of whole milk containing approximately 500g of D-glucose was either suckled or placed directly into the rumen according to the schedule in Table I. For trials II and III, a centrifugal pump was used to force the solution into the rumen of controls because of delays encountered in voluntary drinking in Trial I. Blood samples were drawn prior to and at timed intervals after ingestion of the milk. The following day treatments were switched for each animal. Specific informa- 17 tion on controls used and time interval between sampling are also shown in Table I. Water was removed from the animals 12 h before each trial to insure rapid suckling of test solutions. TRAINING TRIAL II: Thirteen heifers were trained using a slightly different procedure. The animals suckled water instead of whole milk. Training was only during mornings. Water was restricted for about 12 hours before each morning feeding. The animals received dry hay ad-libitum and 1 kg of a grain mix per day. After 8 days of training, water was gradually re-introduced to animals that suckled willingly. By the tenth day only 2 animals required water deprivation to encourage suckling. Rumen By-pass Determination The basic protocol was the same as for other by-pass trials but water containing 500g D-glucose was used instead of milk. Control animals received the same amount of glu- cose in 1 kg grain. Blood samples were drawn throughgjugular cannulae prior to and .5, l, 2 and 4 hours after ingestion of glucose. On the second day, treatments were reversed. Water was again witheld overnight before each trial day to insure rapid suckling of the glucose solution. Production Trial Eight animals trained to suckle were selected on the basis of willingness to suckle and increase in blood glucose during rumen by-pass trials. They were used in a production trial to test the effect of suckling on milk yield and com- position. A two-period changeover design was used with per- iods lasting three weeks. 18 mcwwoow aoumm mason c was 4 .N omazncau amass can“ .H .~\H .ouomom smasmsh one» noeaoum eoaxuam H mm oEwm HHH wcwuoom poems muso: n can :oazu :w v .N .H .oaomom :fio> Heme can» :anoum eoaxuzm H mm osmm HH mcwwoom omoozam Hague mono: v moom + xafie use N .H .ohomom :wo> Heme SHHmsuoz Masha eoaxosm odes: muouwa e H moses onEmm Aaouucoov mafiHnEmm eooam woon N uaosumoue H unusumouh :owusaom amass cage .HOhudoo mo vogue: .uomD .mawamewm mo venues ecu mcofluzaom .mamfiue :owuecfiahouon mmmmuxm :on:«--.~ canes 19 Animals were randomly assigned to either a suckled group or a control group. The suckled group was allowed to suckle up to 15 liters of whole milk daily which provided approxi- mately 500g of milk protein. The control group received daily 500g of casein in the concentrate. All animals were fed ad- libitum a mix of 50 percent corn silage and 50 percent haylage and concentrate at 1.0 kg per 2.5 kg milk. The concentrate allowance was adjusted weekly. The silage mix was fed at approximately 0900 hours and grain at 1400 hours. Feed left in the manger at 0700 hours was removed and weighed. Ingredient composition of the concentrate is shown in Table 2. Metal holders for nipple pails were placed just above the feed manger of each animal, so that cows had unobstructed access to feed but could also reach the nipple pail (see Plate 2, Appendix). The pails were filled twice daily with whole milk for the suckled group and water for controls. Consump- tion of suckled milk, feed weighbacks and milk yields were recorded daily. Body weights were determined weekly. The whole milk used for the supplement was taken daily from the bulk tank at the MSU Dairy Cattle Center. Whole milk, silage mix concentrate were sampled weekly. Milk samples of two consecutive milkings were composited from each cow twice weekly, usually on Monday P.M., Tuesday, A.M. and Thursday, P.M., Friday, A.M. Tail vein blood samples were collected on Monday and Thursday of each week. After three weeks, treatments were switched. 20 Table 2.--Ingredient composition of concentrate used through- out the experiment. Ingredient % Ground Shell Corn 54.0 Rolled Oats 26.5 Soybean Meal (50%) 11.5 Molasses 5.0 Trace Mineral Salta 1.0 Dicalcium Phosphate 1.5 Limestone .5 Vitamin A 4400 lu/kg Vitamin D 400 lu/kg aTrace mineral salt contains a guaranteed minimum of: .35% Zn, .12% Fe, .15% Mg, .03% Cu, .005%Co, .007% I, and 96.00% NaCl. 21 Near the beginning and end of each treatment period, a glucose tolerance test was conducted on each animal receiving the suckled whole milk. Approximately 500g of glucose was added to the milk on the morning of the test. Blood samples were drawn from the tail vein prior to and at 1 and 2 hours after ingestion of suckled supplement. Final Rumen By-pass Trial After the production trial, S cows that had previously been trained, and were still suckling satisfactorily, were used in a final trial to determine rumen by-pass. The objec- tive was to compare suckling to normal drinking and observe the efficacy of rumen by-pass for the two delivery methods. The trial was held on 5 consecutive days and the schedule of treatments for each animal is in Table 3. Blood samples were drawn from the tail vein prior to and at l and 2 hours after treatment 5 . Handling and Processing of Samples Feed: Silage mix, concentrate and casein samples were composited for each period. Concentrate was ground through a 50 mesh screen and silage in a model 84142 Hobbart Silage 1 Dry matter, total nitrogen, acid detergent fiber Chopper. (ADF), and acid detergent nitrogen (ADN) were determined on each composite sample. Dry matter was determined by drying in a forced air oven at 100 C for 48 hours. Total nitrogen was determined by 1Hobbart Manufacturing Company, Troy, Ohio. 22 Table 3.--Schedule of treatments for final by-pass triala. Animal Days 1 2 3 4 1470 T S N S N 1482 N T S N S 1486 N S T S N 1503 S N N T S 1509 S N S N T a500g glucose in 4 liters water was: T = tubed into rumen S - suckled N - drunk normally 23 Kjeldahl (AOAC 1965) as modified by Wall and Gehrke (1975). Acid detergent fiber and ADN were by the Van Soest method (Goering and Van Soest, 1970). Milk: A11 milk samples, including those of the whole milk supplement were analyzed within 48 hours after sampling. Milk fat was determined by the Babcock method; milk protein by the Udy dye method (Udy, 1971); and total solids by drying 3 m1 at 90 C for 3 hours in a forced air oven. Blggd: Except for those samples taken by jugular can- nulae in some by-pass trials, all blood was drawn from the 2 tail vein using single draw needles with 15 ml vacutainer 3 Blood tubes were placed in the cooler at 8-10°C tubes. immediately after collection for 5-6 hours and then centri- fuged for serum separation at 6500xg for 20 minutes. Serum was drawn off with a pipette and placed in 7 dram plastic 4 for storage at -20 C until analyzed. vials Glucose Tolerance Tests: Those samples collected to determine rumen by-pass of sugar were analyzed for glucose using the coupled system of glucose oxidase and peroxidase.5 The values obtained were plotted against time of sampling and analyzed statistically. Production Trial: Serum samples collected during the production trial were analyzed for glucose as previously 2Single Draw Vacutainer Needle (silicone coated, 20 G). Becton-Dickinson, Rutherford, N.J. 07070 3Vacutainer, non-sterile, 15 ml. Becton-Dickinson, Rutherford, N.J. 07070. 4Fisher Scientific Company, Pittsburg, PN. SWorthington Biochemical Corporation, Freehold N.J. 24 described and serum urea-N according to Okuda (1965) and Kulasek (1972, 1976). Statistics Glucose tolerance tests: Paired t tests were used to compare mean serum glucose levels at l and 2 hours after feeding (Steel and Torrie, 1960). Production Trial: The analysis of variance for each of the parameters in this trial was a balanced single crossover experiment (Gill, 1978) according to the model in (l): (1) Yijk = u + Di + Pj + Tk + E(ijk) Where Xijk is the observed value in the ith subject, jth period and kth treatment; u is the overall mean; Di is the effect of the ith subject; i = 1, 2..6; Pj is the effect of the jth period; j = 1,2; Tk is the effect of the kth treatment; k = 1,2; E(ijk) is the residual error. Table 4 shows the degrees of freedom for each source of varia- tion. 25 Table 4.--Sources of Variation and degrees of freedom for model used in production trial. Sources of Variation d.f.a Cows 5 Periods 1 Treatments 1 Error 4 TOTAL 11 a. degrees of freedom RESULTS AND DISCUSSION Training Trials Four of the 6 animals were suckling successfully 10 months after the beginning of the first training trial (Table 5), and only 2 at 10 months of the second training trial (Table 5). Animals were considered to be suckling success- fully when an animal would readily suckle 4-8 liters of solu- tion (water or milk). The results of this study indicate that 2 year old heifers can be forced to re-initiate the suckling habit (See Plate 1 and 2). Inducing thirst in the animal is first necessary to stimulate a desire to suckle. In the first training procedure, feed withdrawal did not stimu- late a desire to suckle. During the first 3 days of this trial, the force-feeding procedure apparently upset the animals, mak- ing them nervous and difficult to work with. Overnight with- drawal from water, however, caused thirst in heifers which they would satisfy through suckling. In both training trials, all heifers showed interest in the nipple after withdrawal of water. This behavior was a learned response. As training continued, less time was needed to force each animal to suckle. At the end of training, most animals would willingly reach for the nipple and no restraint was necessary. Although time required for consumption of the desired amount of fluid was not recorded, it was reduced as the training period 26 27 Table 5.--Results of Training Trials. NUmber of animals suckling successfully at several times after beginning of training. Time after beginning Number of animals of training sucklinga b let trial 221 trial 3 days 0C 13 1 week 5 13 1 month 4 8 2 months 4 4 10 months 4 2 aSix heifers used in Trial 1. bThirteen heifers used in Trial 2. Water was restricted from beginning of training and returned after 2 weeks. cWater was restricted after this point and returned after 2 weeks. 28 progressed. Approximately 10-15 minutes were required for the animals to consume 4-5 liters of fluid at the beginning of training, but this was reduced to less than 5 minutes by the end of training. Persistency of the suckling habit after training was greater in the first trial (Table 5). It is difficult to assess the exact reason for this difference, but several possibilities exist: 1.) Suckling twice daily in trial 1 as opposed to once daily in trial 2, even though after 2 weeks the animals in trial 1 were allowed to suckle only in the mornings. Whether this 2 weeks of twice-daily suckling caused a greater desire to suckle 10 months later is not known; 2.) Whole milk was used to train animals in trial 1 and water in trial 2. Hence, the animals might have remem- bered the more palatable taste of milk. However, after the training periods of both trials, water was used to maintain suckling; 3.) A third possibility is that fewer animals were trained in trial 1 and more time was devoted in training each animal. Cows suckling on one another is an undesirable trait in the dairy industry. One recommendation for cows exhibiting this behavior is to cull them. The cows trained in this study were released from stanchions with the remainder of the herd for 2-3 hours per day, but were never observed sucking other cows, nor did they show any desire to do so. Apparent- ly, these heifers, after being trained to suckle, made no association between milk from the nipple and that which might 29 be obtained from another cow's udder. Rumen By:pass Determination The method used to determine rumen by-pass occurrence has previously been used by other workers (Huber et a1. 1967; Robinson et a1. 1976). The rapid rise in serum glucose after suckling showed that suckled glucose by-passed the rumen. Table 6 lists the mean serum glucose levels for each treat- ment from all the animals in the four by-pass trials. An aver- age increase of 20 mg/100 ml was observed for heifers which suckled glucose with the peak at 2 hours post-feeding. There was little change in blood glucose when glucose was placed directly in the rumen. Figure 1 plots the values shown in Table 6 against time of sampling. Figures 2 and 3 indicate the difference in responses for two individual heifers after suckling the glucose solution; one increased greatly in serum glucose (Fig. 2) the other showed showing no increase (Fig. 3). While both of these heifers suckled actively, the animal repre- sented in figure 3 showed a failure of closure of the eSOpha- geal Opening into the rumen. Only 4 of the 19 animals studied showed no rise in serum glucose after suckling. Three of these were not active sucklers. Thus, all but one of the heifers that suckled actively actively training showed a rapid rise in serum glucose. This increase was usually in excess of 30 mg/100 ml. The peak level for the suckled group shown in Figure 1 was less than 30 mg/100 ml above controls because animals that did not obtain by-pass were included in the mean. Figure 4, which includes only values from those animals that obtained rumen by-pass, shows increases are 30 Table 6.--Mean serum glucose levels (mg/100mml) for all animals in the 4 by-pass trials. Time Control Suckled oa 47.44 48.51 .sb 44.14 56.70 1a 50.44 62.92 2a 52.78 68.08* 4a 54.64 61.38 6c 64.59 64.26 a Means of 37 values. b Means of 25 values. c Means of 15 values. * Significantly different (P<.l). 31. .335 $3.43 5 3258 Sm com :25." one. 35 333% pooma .8 8303 .853 3833 o» omcommow omougm Eom 1H 0.53m 009m Ammaorg mzuh ooo.m ooo.e ooo.m ooc.~ Doc.“ 0 x 1. u x u .4 x x x I. .4 o 8:63 lar .éo.o~ _o.c+coo IT. ozmomm .bo.ov .oo.om 00.2: (WM 001 83d OH] 3803010 HOBBS 32. .mmme->n cease mcmcwmuno Hmewcm pow omousfim ou omcommo» omounflm Escom --~ ocsuwm Amaze: us: ooo.m _ooo.m oco.¢ cow.m ooo.~ cow.~ o .fim.mm .r .fim.mn o.o- (IN 001 334 ON) 3903010 unaas 33. .mmma->n cease mewcwmuno uo: Hweficm pom mmousfim ou omcoamop omousfiu azuom --m opsmwm Awmnorg msz ooo.m ooo.m coo.¢ ooo.m ooo.~ ooc.~ o i x 1. x l l 1 u x 1 l a 826% 11.. :oo.o~ _0c+coo .ITI ozmom_ .854 I.HuII I .oo.om 0.0.”: ('IN 001 83d 01413903010 HOBBS 34. .mmme->n mcmcwwuno mHmeew >Hco wow noes» esp can“ mauuocwv woomaa so eonUSm wocuflo omoozfim cu omeoemop omousfiw eshom --e owsmwu Amazozw msz ooo.m ooo.m ooo.w ooc.m coo.~ coo." o u x u u x t a x l v v u uo_xo:m til . .bo.o~ _0c+coo .ITI ozmowJ eco.ov 00.00“ [1N OOI 83d ON] BSOOOWO “0838 35 greater for animals in which by-pass was confirmed. Table 7 lists the mean values plotted in Figure 4. The final by-pass trial was conducted to determine if animals previously trained to suckle would obtain by-pass when drinking normally. The results of the first trial, where normal drinking was used as a control, suggested such a response in 4 of the 6 heifers. Normal drinking was com- pared to tubing directly into the rumen and suckling. Table 8 lists the differences in mean serum glucose level between the 0 and 2 hour sample for the 5 animals used. Only one animal, 1503, showed a large initial rise in serum glucose after normal drinking. The following day, when normal drink- ing was again tested on the same heifer, no rise was observed. Number 1503 did show a significant increase when the glucose solution was suckled. On the occasion when the increase after normal drinking was observed, the entire test solution was consumed within 1 minute after initiation of drinking. This may have caused a portion of the solution to flow down the esophageal groove and escape rumen fermentation. The animals in the production trial were chosen on the basis of successful suckling activity and positive by-pass. Table 9 lists the mean serum glucose levels for the suckled animals in the production trial and Figure 5 plots these values against time of sampling. The average level at 2 hours was 37 mg/100 ml above the 0 hour level. As Figure 5 indicates, these animals continued to obtain rumen by-pass throughout the trial. 36 Table 7.--Mean serum glucose levels (mg/100 ml) for only animals obtaining rumen by-pass. Time Control Suckled 03 44.84 48.19 .5b 42.21 64.72 la 46.39 71.75* 23 46.85 79.51* 43 51.83 65.35 6c 50.40 54.28 a Means of 31 values. b Means of 19 values. c Means of 15 values. 3 Significantly different (P<.05). 37 Table Table 8.--Difference in mean serum glucose (mg/I00 ml) between 0 and 2 hours after administration of treatment . Animal Day 1 2 3 4 5 1470 -2.0 T 25.6 S .8 N 14.8 S -5.0 N 1482 -l.6 N -3.0 T 28.2 S -3.8 N 27.5 S 1486 -5.0 N -l.2 S -l.9 T -7.0 S 2.9 N 1503 21.1 S 19.7 N -4.0 N -6.0 T 25.1 S 1509 -7.1 S -4.0 N -3.8 S 0.0 N -2.6 T a. T = tubed into rumen S - suckled N = drunk normally 38 Table 9.--Mean serum glucose levels (mg/100 ml) two hours after ingestion of 500g glucose for animals in production trial. Time Serum Glucose (mg/100 ml)a 0 45.98 1 71.48* 2 82.88** a aIncludes 12 values in each mean *significantly different from 0 hour (P<.05) **significantly different from 0 hour (P<.01) SERUM GLUCOSE (MG PER 100 ML] 39. Figure S-- Serum glucose response to glucose for animals in production trial. 100.0 80.00 60.00 40.00 20.00 fi U l .500 1.600 1.500 TIME (HOURS) 2.000 40 Production Trial Two of the eight animals used in this trial were not included in the statistical analysis. One of these had deve- lOped ketosis and was also Operated on to correct a displaced abomasum. As a result of this, the heifer stopped suckling. The other heifer also lost interest in suckling and consumed less than 30g milk protein per day. Thus, the data reported are means of values obtained from 6 cows. Feed Analysis: Ingredient composition Of the concentrate used has already been listed in Table 2. Analysis Of the con- centrate, silage mix, casein and milk supplementare shown in Table 10. The percent protein in the total ration was 12.3 for the suckled group and 13.5 for controls. Feed Intake: Table 11 lists intake of nutrients for each group. Consumption Of whole milk through nipple pails did not affect total dry matter, silage and concentrate intake. The control group had 130g/day greater supplement intake than the suckled group. The control group received a constant amount (500g) of supplemental casein in the concentrate daily. The concentrate was usually completely consumed, therefore 450g of casein entered the rumen daily in controls. The supplement intake for the suckled cows, on the other hand, was quite vari- able. Table 12 lists the protein intake from whole milk for each of the 6 cows that completed the production trial. These ranged from 200-454g with a mean of 320.5g. Only one animal, 1481, approached the goal Of 500g suckled protein. The actual 41 Table 10.--Dry matter content and concentration Of nutrients in the dry matter of feedstuffs used in the production trial. Feed 0Ma Total N ADNb cpc ADFd NELe Concentrate 89.8 1.92 .20 12.00 6.15 1.81 s.e .47 .07 .02 .32 .39 -- Forage mix 44.12 2.54 .23 15.87 30.65 1.43 s.e. .79 .04 .01 .21 .54 -- Casein 92.30 14.54 -- 90.90 -- -- s.e. .64 .13 -- .54 -- -- Whole milk 12.2 4.69 -- 29.31 -- -- s.e. .32 .09 -- .38 -- -- a. dry matter b. acid detergent nitrogen c. crude protein = total N x 6.25 d. acid detergent fiber e. estimated net energy for lactation f. standard error 42 .unmwoz keen mo ueouuom m we menace Zn ohm monogueoumm cw mosam>n .nouno mandamumm .fimc.vav peowommee sausagemflemfim.. .aHo.vac Semummmee saunaUAMAamflm . o.m~ e.e~ o.m~ NNH. n .8.m~ m.e~ sae\fiaoz .mxmoeH Hmz 0H.N NH.N 4H.~ has. H. .e~.~ mo.~ sae\mx.6xauee eaopoaa Hence I mmwmwn zne - :«ououm Mafiev m.som m.ooe N.mmm m.m~+ ..cme m.o~m Aae\m .mxapae “eosofiadzm flm~.mv ”ON.mL fim~.mv .. m-.mc nfim~.mo m.o~ m.oH no.6H me. + o.oH 5.8“ sme\mx .mxap:H 46438: Aug N IH :moa m.o.m HOhucoo woaxuam vofiwom Hamuo>o «cospmoub oxmucn Hmz use oxmpcm seaweed Hence .mxaueH aeosofiddsm .6xaueH 5: :6 ea“: mace: eofixusm mo puommm--.HH menus 43 amount of milk protein reaching the abomasum was probably somewhat lower than the values listed in Table 12. Work by Wise and Anderson (1939) suggests that there may be spillover of liquid as it is directed down the es0phagea1 groove in Older animals. The fact that the groove fails to develop proportionately with the rumen (Wester, 1926) also suppports this hypothesis. Therefore, the values listed in Table 12 are considered to be the maximum amount of supplemental milk protein by-passing the rumen. Total protein intake (Table 11) therefore, was greater for controls, primarily due to the con- sumption of greater amount of supplemental protein. The total protein intake as a percent of NRC require- ments was 103.8 for controls and 92 for the suckled group. NE1 intake, as a percent of NRC, was 106.7 and 99.5 for res- pective groups. Thus, the nutrient intake was not so high as to mask a response from protein supplemented to the abomasum (Clark, 1975; ¢rskov et al. 1977). There were no effects of periods for any of the intake parameters. Production Effects: Suckled supplemental milk protein increased milk protein yield (P<.05) 70g over control animals (Table 13). Milk fat yield was also increased by approximately the same amount, although not significantly so. Milk yield was increased by almost 1 kg/day this also was not statistically significant (P<.20). This 5% increase in milk yield, however, coupled with the 10% increase in protein yield may have con- siderable economic significance. According to Smith and Johnstone (1978) and Johnson (1971), reasonable estimates 44 Table 12.--Whole milk protein consumption through nipple pails for each cow on production trial. Cow Number Consumption (g/day) 1481 454.0 1482 199.7 1483 238.3 1490 295.1 1503 372.3 1470 363.2 45 .unoEuwouu woe mzou News .nouwo enmeawumm .AH.VaU uaotommee saunaUAmeamfim.. .fimo.vav aeotommfle Aflpeauamaewam . ~.ose m.~we o.~ee ”H.“ .m.mme H.wcw m .efioas assuage MAS: H.500 ~.4mo A.smo AN u A.H~8 o.~ao m .eamfis use AHA: wm.m mm.m mm.m mo.n_ ..Hm.m as.m * .eaopoud AHA: AH.m mm.N ~c.m may“ mm.~ NH.m * .umm mam: 4.HN H.- w.H~ so.“ ~N.HN o~.- we .edofls xflmz N, H :mos m.O.m HOhuqou UOHwosm woflwom Hamuo>o ecosumonh xfifiz .eflooowa xfiez .unouwom cwououm Maw: can usoowom you use and EH“: .xflez mo ease» no ea“: mace: eoflxusm mo pucmmm--.w~ oflnae 46 for protein differentials range from 3-6 cents per tenth Of a pound Of protein. Then for every tenth of a point the pro- tein percent is raised, the dairyman could expect a increased income of 3-6 cents per hundredweight. If one assumes the price of milk to be $10.00 per cwt., with a 6 cent differen- tial on protein test and a 9 cent differential on fat test, then for the cows in the study: 1.) The suckled cows lose 36 cents on fat (3.5-3.1 = .4 pct. points and x.09 = .36) but gain 6 cents on protein (3.6-3.5 = .1 pct. points.), making the price per cwt. $9.70. 2.) The control cows likewsie lose 54 cents on fat and gain nothing on protein so the price per cwt is $9.46. Thus the value of the milk produced in one day by the suckled cows was $4.73 and that for the controls was $4.41. Even when both groups are not penalized for the low fat content and just credited for increased protein, the value of the average day's milk for the suckled cows is 25 cents greater than controls as calcuted in (3) and (4). 3.) 10.00 + .06 = 10.06/cwt. or .1006/1b .1006 x 48.84 lbs = $4.91 for suckled cows. 4.) 10.00/cwt or .1/lb .1 x 46.64 lbs 8 $4.66 for control cows. One must also consider the cost of producing the extra milk. In this case 320 g of casein, at 72 cents6. 6Milk Specialties Inc., Chicago, 111. 47 per lb, the daily cost of the casein supplement was 51 cents giving a 26 cent daily profit decrease. If, however, a soy- flour solution were used and the same results Obtained, the daily profit increase would be 15.5 cents, assuming a cost Of 13.25¢/lb6 per 1b soyflour. Unless milk yield and protein content could be increased even further, however, the increased labor involved in training the animals to suckle and maintain- ing the suckling habit would make this scheme of supplementa- tion unfeasable to the average dairyman. Since whole milk was used as the supplement, it is diffi- cult in this study to attribute the effects only to protein. Milk fat was consumed as well as protein. The slight increase in fat yield could have resulted from the highes fat intake (Bitman et a1, 1973; Mattos and Palmquist, 1974; Wright et al. 1974). For discussion purposes, it will be assumed that the effects on protein yield were influenced by suckled protein only. In gross terms, efficiency Of protein utilization (total milk protein out total protein in) was 39.3% and 32.4% for the suckled and control groups, reSpectively. Figure 6 plots the increase in milk protein against the intake of suckled protein for each individual animal. This relationship is linear and has a regression coefficient of .87. A similar response was noted by Orskov et a1. (1977). A more desirable way to look at this, however, might be to INCRERSE IN PROTEIN YIELD [GRRMS PER DRY) Figure 6-- Effect of suckling milk protein on increase in 48. milk protein yield. 200.00 C) 150.00” 100000"- Q) at) 50.00' C) (D G % uL i i 0 100.00 200.00 300.00 400.00 SUCKLED PROTEIN (GRHMS PER DRY) 500.00 49 estimate the amount of protein reaching the abomasum. Bucholtz and Bergen (1973) suggested 16.5g microbial protein production per 100g organic matter when rumen turnover of pro- tein was 26%. Protein at the abomasum in this study was cal- culated as in (g) and (5): (4) DOM - (IT x DM x OM x TDN) i=1 (5) ABPR = DOM - (TPXBP) X .165 + (TPXBP) Where DOM is intake of digestible organic matter, kg; i is 1 for silage mix; 2 for concentrate; and 3 for casein supple- ment in rumen. IT is intake of feed on as is basis, kg; DM is dry matter in feed, %; OM is dry matter minus ash, %; TDN is total digestible nutrients, %; ABPR is total protein at abomasum, kg; TP is true protein, kg; BP is plant protein by-passing the rumen, %; .165 is kg microbial protein per kg DOM. Estimates of total protein available at the abomasum at several rates of by-pass are listed in Table 14. If 40% of the pro- tein entering the rumen were by-passed in to the abomasum, both groups of cows would be received approximately the same amount of protein at the abomasal level. The increased milk protein yield for the suckled group then might be explained by the better utilization of the milk protein entering the abomasum. 0n the other hand, if one assumes that there is no by-pass except for that protein that is suckled, then the 50 Table l4.--Total protein (kg/day) available at the abomasal level for cows in this study. True Protein bypassing Treatment the rumen, % of intake suEkch Control 0 1.57 1.43 10 1.72 1.62 20 1.86 1.81 30 2.01 1.99 40 2.15 2.18 51 efficiency of conversion of abomasal protein to milk protein is the same for both groups, as calculated in (6) and (7). (6) suckled: 100 (.808/1.57) = 51%. (7) control: 100 (.735/1.43) = 51%. The production results obtained support the findings Of abomasal infusion studies. If the amount of suckled protein could be increased, the production response may even be greater. Other Effects: Mean levels of urea-nitrogen and glucose in the serum of cows on production trial were not different between treatments (Table 15). Body weights of the animals in each treatment were also not different and were 513.2 kg and 514.3 kg for the suckled and control groups respectively. Conclusions Two year old heifers can be trained to re-initiate suckling. The suckling habit continued for up to 10 months in some animals. More work is needed on maintaining the suckl- ing habit for longer periods. The majority of animals that suckled actively obtained rumen by-pass of the suckled fluid. ( When whole milk was suckled and by-passed the rumen, milk_ yield was increased by 5% and protein yield by 10%. This method of rumen by-pass certainly has merit from a research standpoint, but may not provide a great enough res- ponse to be commercially feasable at the present time. 52 Table lS.--Effect of sackling whole milk on mean serum levels of urea N and glucose. Suckled Control s.e.b Urea-nitrogen 8.32 8.98 i .87 Glucose 48.51 47.44 ‘12.32 a. 48 values per mean. b. standard error BIBLIOGRAPHY BIBLIOGRAPHY Allison, M. J. 1970. NitrOgen metabolism of rumen micro- organisms. In Physiology of Digestion and Metabolism in Ruminant. A. T. Phillipson, ed., Oriel Press Limited, Newcastle upon Tyne, England. AOAC. 1965. Official methods of analyses. 10th ed., Association of Official Agricultural Chemists, Washington, D. C. Barry, T. N. 1972. The effect of feeding formaldehyde treated casein to sheep on nitrogen retention and wool growth. N. 2. Journal of Agric. Res. 15:107. Barry, T. N. 1973. Effect of treatment with formaldehyde and intraperitoneal supplementation with D-L methionine on the digestibility, and voluntary intake of silage of sheep. Proc. N.Z. Soc. Anim. Prod. 32:48. Bitman, J., L. P. Dryden, H. K. Goering, T. R. Wrenn, R. A. ' Yoncoskie, and L. F. Edmonson. 1973. Efficiency of transfer of polyunsaturated fats into milk. J. Amer. 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' Zelter, S. 2., F. Leroy, and J. P. Tissier. 1970. Annales de Biologie Animale, Biochimie, Biophysique 10:111. APPENDIX Plate 1: Typical view of feeding procedure with a trained animal. 61 Plate 2: Metal holders were used in the production trial to give animals access to milk throughout the day. 63 "IIIIIIIIIIIIIIIIIII“