SOME FACTORS AFFECTING INTAKE OF ALFALFA SILAGE BY DAIRY HEIFERS Thesis for the Degree of Ph. D. MICHIGAN STATE UNIVERSITY James P. Everett, Jr. 1963 4.... y THESIS This is to certify that the thesis entitled Some Factors Affecting Intake of Alfalfa Silage by Dairy Heifers presented by James P. Everett, Jr. has been accepted towards fulfillment of the requirements for __£h'_D'_ degree in _Da}_I_‘_y__ 5/757 Major professor Date February 22, 1963 0-169 LIBRARY Michigan Sun University WC!!! 8043 FACTORS ”EWING INTAKE OF MINA BIL-A- BY MIR! HEDERB by Jmnes P. Everett, Jr. Four experiments with dairy heifers were carried out in an attempt "to elucidate the reasons for observed dry matter intake differences of heifers fed solely alfalfa hay or silage. In the initial trial to establish intake differences among forages, average daily dry matter intakes per 100 lb. liveweight and average daily gains of heifers fed by andvilted silage (25$ dry matter) were significantly greater than those of animals fed direct-cut silage (17.9% dry matter). In the second trial lowering the pH of hay to approximately that of silage by adding dilute hydrochloric acid and adding Silo-Joy to wilted silage to alter the flavor had no significant effect on dry matter intakes or average daily gains. Adding ground hay to the direct- cut silage to increase the dry matter content resulted in greater dry matter intakes and average daily gains- The effect of moisture content per; __s_e on dry matter intake was detemined in a third trial. Increasing the moisture content of wilted silage by. 5 or 10$ at feeding time had no significant effect on dry matter intakes or average daily gains. The possibility that acetic acid inhibits hypothalmnic feeding centers was tested by adding this acid to hay at feeding time in the fourth trial. This addition had no effect on. James P. Everett, Jr. dry matter intakes or gains of heifers. Possible reasons for the reduced dry matter intake fran silage in cmparison with hey are discussed. SUE PACI'ORS merino INTAKE OF ALFALFA 8m BY DAIRY mums By va James Pf’cEverett', Jr. ATEESIB Submitted to Michigan State University in partial mlfilJment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Dairy - 1965 4’ 25"”?6 / 17/2//;_‘3‘ AW The author wishes to express his appreciation to Dr. N.P. Ralston, Assistant Dean of Agriculture, for award of the Graduate Assistantship and provision of the facilities for conducting the study. Sincere appreciation is also expressed to Dr. c. A. Lassiter, Professor of Dairying, for his excellent guidance and counsel during the conduct of the study and his patience during the writing thereof. The writer is also indebted to Dr. 0. r. Huffman, Professor of Dairying, Dr. ms. nnery, Associate Professor of Dairying, Dr. E. P. Reineke, Professor of Physi- ology and Pharmacology and Dr. R. U. Byerrum, Professor of Chemistry, for welccne advice and for critically reading the manuscript; to Mr. R. E. Reid and Mr. L. A. Reid for assistance in caring for the animals; and to other staff members and yadnate students who provided advice and assistance at various times during the study. mowerron TABIIEOFCOE'MS LISTOPTABIES........ usrormncms... MOFLW§.-. . . . O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O on... [Dry matter intake or performance of dairy calves and heifers red 9888 811583 -0 O p O O O O I O O O O O O O O O O O .0 O O 0 Factors possibly involved in reducing dry matter intakes of ' Wtsfedsilage......s.........‘.'. Factors influencing the dry matter intake of ruminants Appetitecontrolinnon-rminants. ... . . . . . . . . . Trial 1. Animal response gdlibitm . . . . . . ...Trial 2. Animal response ground hay to forages . Trial}. Animal response Trial 1}. Animal response WSWHH... to alfalfa silages or hay fed ' WPROWOOOOOOOOOOOOO0.000000.0 O O O O O O I O O O O O O O O O O to adding acid, Silo-Joy or ' oereeeooeeeeooe.ooo'o to adding water to silage when fed'. to¥adding acetic acid to.h'ay_ eeeoeeoeeee‘eeepeoo Trial 1. Animal response to alfalfa silagesi or bar fed ' glibitm- o 0.000 0 Trial 2. Animal response 0 O O O O O O O O. O O O O O O O O O to adding acid, Silo-Joy or ' lmmt°£oragesee_eeeeo.reeoeeoeeee‘e Trial 3. “Animal respOnse to 'adding water to silage when fed. Trial It. Animal response to adding acetic acid to hay . mmHOOOOIOOOOO‘OO DISCUSSION WY 0 O O O O O O 0 O I O O O O O O O O O O O O O O O O O O O O O O O O C O O O 1? 16 31 39 I+3. 1+3 1#5 1+5 53 56 59 85 Table I3 LISTOFTABLES Chemical composition of alfalfa forages utilized in Trifl- l O O O 0‘ O O O O O O O O 0 O O O O O 0 O O O 0 Dry matter conlwlption’and average daily gains in Triall..................‘..... Average daily dry matter intake per heifer by weekly ' ”rim in Tris“- l .0 O O O 0 O O O O O O O O O O O 0 Chemical composition of alfalfa forages utilized in‘ maaee'e-eeeeooooeeoeeoeeeoee Dry matter consumption and average daily gains in' Trial 2 O O O O O O O O O O O O O O O O. O O O O O O 0 Average daily dry matter intake per heifer by weekly' ' peflwinTrialeoeeeoeooo‘eoeeoooe Dry matter content Of silage fed during Trial 5' by “W periOdB O O O O O 0 O O O O 0 O O O O O O O 0 Dry matter consmnption and average daily gains in ' mu- 3 O O O O O O O O C O O C O C C O C O 5 O O . O 0 Average daily dry matter intake per heifer by weekly ' ”rims in Trial 3 O O O O O O O O O O O O O O O O O Drymatter content ofhay and orts in Trial It . . . . . Dry matter intakes and average daily gains in Trial It . Average daily dry matter intake per heifer by weekly Daria“ in Trifl- h 0 O O O O O O O O O O O O O O O 00 iv Page 1+7 50 51 53 51+ 55 55 56 57 57 Amman: TABLES Table Page 1 Dry matter losses in stack silos during Trials 1 and 2 . ‘ 86 2 Dry matter consumption and average daily gains in kid 1 O O O O O O O O O O O O O O O O O O O O O O O 87 5 Dry matter consrnnption and average daily gains in mu 2 O O O O O O O O 0 O O O O O. O O O O O O O O O 88 It Dry matter consumption and average daily gains in‘ ma 3 O O O O I O O O O O O O O O O O. O l O O O O O 89 5 Dry matter consmsption and average daily gains in maheoeoooeeeeeeeeeeeeeeeee m ww- . . INTROIXJGIION Forage evaluation has.” long been a problan attracting the attention of animal husbandmen and ruminant nutritionists. Methods of forage evaluation are numerous, ranging from the detennination of the net energy available from the forage to the msbandman' s appraisal of the leafiness and color of his hay. Only the chemicalanalysis 0f the 1-:- plant is relied upon to assess the feeding value at times and on the other hand, the animal" is sometimes used in this‘ determination. Nevertheless, the quantity of forage VOluntarily consumed by the animal has not been shown to depend on any specific nutrient or energy ; content of the feed. Fran an econcmic standpoint, therefore, the voluntary intake of a forage is of greater import in forage evaluation at present than the determination ‘of nutrient or enerw concentration. Fran a research standpoint, the continued search for factor( 3) , lpWsical Or chemical, in the forage which influence“) voluntary intake is needed. Further, the relationship of these factors to the animal's physiological mechanisms is required. Dry matter intake of cattle fed alfalfa silage has been shown repeatedly to be less than that of comparable animals fed alfalfa hay harvested concurrently from the same plot . The purpose of these trials was to investigate several factors which could possibly explain the observed differences in dry matter intake of dairy heifers fed various hay and silage rations. These factors are (a) acidity (pH), (b) moisture content, (c) flavor, and (d) acetic acid content. REVIEW OFLI'JIERAIURE Hillman (1959) , in a canprehensive report, has reviewed the dry matter intake and performance of dairy cattle fed grass silage, hay or soilage and the effect of silage preservation methods on intake. It is apparent from this report that cattle usually consume less dry matter from grass silage than fran hay. Yet the reason( 3) for this difference ranain( s) an enigma. The current studies are concerned with factors possibly contribu- ting to this difference in dry matter intake. This review, therefore, “magnets-7's. la. $fi. b.1r' includes discussions of the dry matter intake or growth of dairy heifer's fed grass silage, factors possibly contributing to this reduced intake and more generally, physiological regulation of appetite in ruminants and non-ruminants . Dry Matter Intake or Performance of Dain Calves and Heifers Fed Grass Silage Silage evaluation studies using young dairy animals usually mploy one or both of two criteria, viz. , average daily gain and/ or dry matter intake. In a recent study, McCullough and Neville (1959) found a corre- lation of 0.711 between dry matter intake and average daily gain; it is obvious, therefore, that average daily gain is not solely a function of intake and hence, in studies of this nature, both criteria used in the evaluation are of interest. 1 In this discussion, grass silage as defined by Savage and Bender (1939) is intended, viz. , a silage made fran ‘any uncured ha crop whether it be true grass such as timothy, a legume such as alfalfa or a green 'cereal such as oats. 2 '— 29.1129. ‘ Although the time of the transition has calfhood to heiferhood in the life of the bovine is ill-defined, a distinction is attmpted in this review since calf-feeding programs are usually such that drastic changes in forages fed result in little effect on growth. For exanple, calves fed oat straw, a roughage hardly lauded for its nutritional worth, to 7 weeks of age made gains comparable to those fed alfalfa hay (Ratcliff, 1959). As the animal becanes older and relies more on roughage to meet its nutritive needs, changes in forage quality or intake are more easily detected in pmrsiological response. 2 Several trials have been conducted in which grass silage was fed to very young dairy animals. Porter and Healer (1951+) fed Holstein calves to 112 days of age on either 2 or 5 lb. of concentrates per calf daily with hay, grass silage, or hay and grass silage free choice. Whole milk was fed to 6 weeks of age. no significant differences in average daily gain attributable to the type of forage offered were found within each grain level. However, dry matter intake from the total ration was significantly lower for silage-fed calves offered 5 1b. grain daily than the other two forage groups offered a similar amount of grain. In a second experiment (Porter and Kesler, 1957) , Holstein calves were again reared to 16 weeks of age using forage and milk feeding .as inathe first trial. A maxim of 5 lb. grain was offered 2 For convenience of discussion, the animal is now ostensibly a heifer. This is a nutritional distinction and would not coincide with the physiological one such as onset of estrus which is used by Frandsen (1958) in delineating the calf-heifer change. 1» to each of the animals in the "three groups. The alfalfa silage group again consumed significantly less dry matter frau the total ration than the alfalfa hay or hay-silage groups to 112 days of age, but the live- weight gains of the three groups during this period did not differ significantly. The report of a third study (Hoover, _e_t 2.1., 1959) at the Pennsylvania station includes no feed intake data. In this trial calves fed fran birth to 16 weeks of age a fair quality mixed hay averaged 186 lb. liveweight gain and a similar group fed excellent quality second growth alfalfa silage made an average 16-week gain of 218 lb. When both forages were fed, calves gained 201 1b. during the . experimental period. .A maximm of 1+ 1b. grain was fed each. calf daily. In a trial (Sykes, gt 51. ,1955) in which dairy calves were fed alfalfa hay, wilted alfalfa silage or both these forages, there was little difference in feed consumption per unit bow weight and only small differences in average body weights between the three groups at 150 days of age. All groups received a maximum of 5 1b.: grain daily during this period in addition to limited whole milk to 60 days of age. A later study (Thanas, 23 51., 1959) supports these observations. Newlander and Hiddell (1957) canpared the feeding value of wilted and direct-cut grass silage using twin heifer calves 5 to 1+ months old. Grain was fed at the rate of 2-45 1b. daily. Calves fed wilted silage consumed 8.5% more dry matter than those offered direct- cut silage and increased 9.7% more in bodyweight than the twin on the high-moisture silage. 31 Y. It appears frm the published reports of experiments in which gass silage replaced hay in the ration of the young dairy calf (to 5 months of age or when gain feeding was reduced below 5 1b. daily) that dry matter intake dropped but the effect was not discernible in average daily gains due to milk and gain feeding practices employed during r this period. L1 Heifers " unfortunately, experiments evaluating silage as a feed for growing i dairy heifers (over 5 months of age) are often confounded by feeding " moderate to large amounts of concentrates. Thus silage has been shown (Schubert, _e_t_ 21., 1940; Keener, £1; .31., 19h9) to give greater average daily gains than hey when fed to heifers receiving 2-5 1b. concentrates daily, and to give smaller gains than hay or ha and. silage when fed to heifers receiving no gain supplement (Bender and Tucker, 1957; Sykes, 21%., 19553 Keener, g}; 21., 1958; Lassiter, gt _a_l_:., 1958; McCullough and Neville, 1959; Thomas, gt 31., 1959). It should be mentioned at this point that dairy heifers have been shown (Converse, 1955) to make satisfactory gowth when alfalfa hay, alone or combined with other boys or corn silage, is the only feed available from 8 0r 9 months to 21+ months of age. Dairy heifers averaging over 700 lb. liveweight were fed (Schubert, . BE g” 19%) either all-silage of varying types, all-hay of poor quality or equal amounts of each in a 125-day trial. In addition, 5 1b. gain was offered each animal daily. Although average daily gains of ml 6 the three respective goups were 1.86, 1.28, and 1.55 1b., the dry matter intake per animal for the forages during the experimental. period averaged lh5.h, 158.7, and 155.8 lb. , respectively. This rather low dry matter intake from roughage was undoubtedly due to the high gain feeding, but regardless of this, dry matter intake was lower for the silage goup than those receiving all or part hay. Keener, gt 9:1. , (19h9) , in a feeding trial with dairy heifers, also obtained geater liveweight gains fran silage than fran hay of the. same crop. The dry matter intake frail silage, however, was censiderably less than that from mow- or field-cured hay. Average daily dry matter intake frcm silage was 7.6 lb. per animal while the hay goups averaged 11.6 lb. Although 2 lb. gain was fed to each animal daily, the increased gain of the silage group could not be explaihed on the basis of T.D.N. intake. In a more recent study of longer duration, Keener, gt _a_.‘_l_.. (1958) found that the addition of 0.75 lb. hay/1.00 lb. body weight daily to ‘an all. gass-silage ration increased body weight gains 16$ and energy consumption 20.5%. Heifers used in this study were fed from 2 dare to 21+ months of age on the respective forages and were given 500 1b. gain during the first 8-9 months of the trial. The goup receiving the silage-limited hay ration averaged 91.; of the normal body weight for heifers of this breed at 2 years of age. Heifers fed the all-silage ration made unsatisfactory gains. A similar study by sender (l9h-2) in which limited hay (5 lb. / animal/day) was added to an all-gees silage ration for gowing heifers, 7 revealed that in height the Guernseys .and Holsteins were only 95.8 and 9’4-Jlf, respectively, of Regsdale’s standards for these breeds at 2 years of age. It was shown earlier (Bender and Tucker, 1957) that dairy heifers fed. timothy silage alone made an average daily gain of 0.67 lb. while a similar group fed timothy silage plus hay made daily gains of 0.80 lb. Henderson and Norton (1950) concluded that yearling dairy heifers made satisfactory gains on grass (60% legume) silage when 5 1b.. of hay was fed each animal daily, although the experimental data appear to confirm this for only one of the three trials. Sykes, at .99.- (1955) comared the T.D.N. intake and growth of dairy heifers fed from birth to 2k months of age either alfalfa silage (35$ dry matter), alfalfa silage plus limited hay or alfalfa hay alone; limitedmilk and grain were fed to 60 and 210 days of age, respectively, and subsequently only forage . Average body weight of the silage group was significantly less than the hay-fed group at both 12 and 2% months of age. The silage-hay group was intermediate. The reason for' this difference was explained by the T.D.N. intakes of the three grows; silage-fed heifers consumed significantly less T.D.N. than the hay-fed group, a difference which was greatest during 5-12 months of age. In trials in which managuent was essentially the same, Thames, gt _a__1. (1957, 1959) confirmed the previous observations. Alfalfa hay has been compared with oat silage in two growth trials using dairy heifers (Lassiter, _e_t_ 51., 1958; McCullough and Neville, 1959). Lassiter, gt _a_.‘l._. (1958), using animals of approximately 580 lb. average initial weight found average daily gains of 0.92 and 0.52 lb. 8 for alfalfa hay and oat silage groups, respectively, and similarly, average daily dry matter intakes of 12.1 and 9.2 lb. These observations were confirmed by McCullough and Neville (1959) using animals of approximately R50 lb. average initial body weight. Average daily gains were 1.51; and 0.96 lb. for the alfalfa bar and oat silage groups, respectively. Mean daily dry matter intakes were 12.1 lb:. for the hay-‘- fed animals and 7.1; lb. for those fed silage. This survey of feed intake and growth of dairy heifers fed silage reveals that animals generally consumed significantly less dry matter than comparable animals fed hay and. also made lower liveweight gains. This has not been interpreted in the literature to mean that hay is superior to silage in nutritive value. When wilted silage and hay were fed (Moore, gt 31., 19%) to dairy heifers on an equal hw-equivalent basis, body weight gains of the silage group were as good or better than the hay-fed group. It appears further, that in studies comparing silage and hay,that the observed differences in intake and performance are more marked with younger animals fed only forage. Thomas, 5}; _a_1_. (1959) found these differences to be most marked at 8-10 months of age, the start of which coincided with cessation of grain feeding. The effect of this feeding regime on growth is less noticeable during l2-2b. months of age. . Thus the exigence in silage feeding is an explanation of the reason for reduced feed intake of silage-fed animals. The remainder of this review surveys the literature pertinent to this topic, and is expanded to (cover mature cattle, other ruminants, and other species where appropriate. 9 Factors possibly Involved in Reducing Dry Matter . Intakes of Rminants Fed Silage Plant, animal and management factors influencing roughage dry matter intake by ruminants are legion and will be surveyed in part in a later section. Scale of the factors shown to influence silage dry matter intake which will not be considered in this review are (1) stage of maturity of the forage ensiled (Marts, at 51., 1959), (2) species of forage ensiled (Marts, _e_t_ $9 1959), (5) the feeding of hay with silage (Hillman, 1959) and (lb) preservatives used in ensiling (reviewed by Hufman,19593 Hillman, 1959). Moisture Content of Silage The moisture content of a forage when ensiled (and subsequently reflected in the product as fed) has been shown to influence the dry matter intake in" numerous studies (Bailey, 35 51., 1955 3; Newlander and Riddell, 1957; Moore, 1958; Gordon, et _a_l_., 1959a) . In these trials wilted silage was consumed in greater quantities on a dry matter basis than 'unwilted silage or silage of higher moisture content. Con- versely, when the water content of. a plant decreases with advancing maturity (mxtcheson, gt 31., 1918), the dry matter intake of animals fed silage free the more mature cuts decreases (Reid, et 51., 1959b). The nature and/or chemistry of the silage fermentation process has been adequately reviewed (wetson, 1958; Bender and Bosshardt, 1959; Huffman, 1959; Barnett, 195%; Langston, _e_t_ g” 1958) and experiments v'v—vv 10 cited in' these reports dmnonstrate that the moisture content of the forage ensiled can greatly influence the chemical nature of the resulting product. Thus, greater attention will be paid here to more critical experiments concerning the effect of silage water content on dry matter intake, studies in which the effects of moisture are not confounded with the effect of plant maturation or the silage fermentation process. Before turning to these trials, however, it is of interest to survey several studies in which silases of high dry matter content have been : preserved and. fed to nnainants. These have not been reviewed since the report of Monroe, gt 51., (1916). An early study (Reed and Fitch, 1917) in which alfalfa silages with varying but low moisture contents were fed to beef cattle indicated that the forages were generally unsatisfactory in nutritive value when preserved in this manner. The dryest silage in this study contained approximately 111% moisture . Bender, gt _a_1_. (1956) ensiled grass containing from 23-55% water (average 111+.th and obtained a black product deemed unfit to feed. Silages were not packed in the silos in this study. Acceptable high dry matter silages, however, have been preserved (Fred and. Peterson, 1921+; Woodward. and Shepherd, 19h23 Rogers and Bell, 1955; Shepherd, _e_t_ 5., 1955). .Woodward and Shepherd (l9h2) made a statistical study of a large number of silages made frcm various forages of differing moisture contents. Cows fed silages averaging 15$ moisture consumed 2h.8 lb. of dry matter daily while animals fed silages averaging 70.6% moisture ingested 21% lb. dry matter daily. Cows were offered each silage for only a 6-day period. Shepherd, gt 31., (1955) fed silages containing 1.1 R6 or 611% water to lactating cows. Average daily dry matter intake per 100 1b. body weight was 2.5h lb. for the wet silage and 2.52 lb. for the high dry matter silage goup. It has been noted that less fermen- tation occurs in silage containing approximately 50$ dry matter than in "normal" grass silage (Mikhin, gt 9.1., 1956; Shepherd, st 91., 1955). The mOisture content of grass silage has been altered in several trials by either adding water (Dodsworth and Campbell, 1952, 1955; Dodsworth, 1951.) or drying the silage (Thomas, 35 31., 1961b) . Com- parison of the dry matter intakes of animals fed either grass silage or vetted hay has also been made (Hillman, 1959) . Dodsworth and campbell (1952, 1955) fed two sheep twice daily grass silage containing 22.66% dry matter and a like number ofanimals the same silage which was reduced to 16.85% dry matter by the addition of water. Treated silage was allowed to soak overnight, resulting in a slight? fruity odor. Both groups consumed the same wet weight of silage. In a second study (Dodsworth, 1951+) , using three sheep per group, silage containing 19.165 dry matter was reduced to 15.855 dry matter. Although the experimental group ingested 5.5% more silage than the control group, 16.7% less dry matter was eaten daily. The control animals averaged 919 g. dry matter intake daily while the vetted-silage group averaged 787 g . Digesti‘bility of dry matter was variable but approximately the same for both groups of sheep during the experimental period. 12 Dried. alfalfa silage, wilted alfalfa silage and. alfalfa hay taken fron the sme field were ccmpared in a 7-month feeding trial with dairy heifers placed on experiment at 5 months of age (Thames, gt 21., 1961b) . m'y matter intakes for the respective groups above were 2.55, 2.52, and 2.66 1b./1OO lb. liveweight daily for Holsteins and similarly, 2.28, 2.25, and 2.77 lb./100 1b. livcweight daily for Jerseys. The addition of molasses to the dry silage during the last month of the trial failed to improve dry matter intake. Camburn, gt g. (1957) , compared the intakes of corn silage and. dried corn silage by dairy cows and found that Ayrshire cows ate more fresh silage while Jerseys preferred the ' dried product. In the interpretation of data from trials utilizing dried silage, cognizance must be paid to the loss of volatile components which results in a product differing from the original in constituents other than water. Colovos, gt g1. (1957) report a lossx;of energy and protein in the drying of silage. Hillman (1959) fed legume grass silage containing 22.55 dry matter, hay taken from the same field or hay vetted to contain approxi- mately the dry matter content as the silage to groups of dairy cows. Dry matter intakes of these respective groups were 2.17, 5.25, and 5.28 1b./1oo “1b. bocnr weight daily; _ Although the effect of water in the ration on appetite will be discussed generally in the following section, it should be documented here that silage-fed cows consumed less dry matter (Foreman, gt g” 1958) and mm. (airman, et al., 1957) than cows fed soilage which contained. a greater percentage of water. 1 .. .1 I I _r u . I , - - _- -l — ’ ‘- l} flysical Pom of Foggg Emailed -- 193g, ChoppedJ Lacerated The effect of physical form of silage on dry matter intake is difficult to evaluate since the alterations reported have been made before ensiling, resulting in different types of fermentation. Thus. the varying end products could possibly effect intake of the silage rather than physical form. No reports have been found which document changes in the‘particle size of the silage Just prior to feeding. The effect of physical form of forage ensiled on the fermentation process has been reviewed by Barnett (1951+) . In laboratory experiments, it has been shown that crushing or lacerating the forage ensiled resulted in a product of lower pH L (de Man, 1952) and higher lactic and volatile acid content (Murdoch, gt g1_. , 1955). Silage preserved in large silos has been shown to contain less lactic acid (salch, gt 5.1., 1955; Murdoch, gt 3.1;, 1955) and more lactic acid (Gordon, gt g. , 1959b) when lacerated prior to ensiling than canparable forage chopped prior to storage. These ananalous results are probably due to the use of different forages of different moisture contents. Further, the particle sizes of the chopped silages were not the sane. Feeding trials comparing the dry matter intakes of animals fed silaees of various physical forms are inconclusive. Gordon, gt g. (1958) found dry matter intakes of 2.01 and 1.8h lb. /100 lb. body weight daily for chopped and unchopped silages, respectively. In a second trial, dry matter intakes were 1.71 and 1.75 lb./lOO lb. body weight I daily in the sane order. Duckworth and Shirlaw (1958) report a ...L ,h. I|_ .- it sialificantly lower} dry matter intake by heifers fed chopped. silage thansimilar animals fed long silage. In studies comparing the digestibility of chopped, long and lacerated silage by cows and steers, Belch, gt git. (1955) found that chopped silage was generally more digestible than unchOpped silage, and lacerated silage was intermediate. It was the opinion of the authors that these differences could be explained by the losses of N.F.E. in the ensiling process. These losses were calculated to be 19.0, 57.0, and out; of the man. in chopped, lacerated and unchopped silage, respectively. Organic Agtd content and pH A notable characteristic of silage is its organic acid content and low pH. In fact, the lowering of pH due to production of these acids has been included (Watson, 1957) in the definition of the ensiling process. Experimental attempts, however, to determine the effects of silage pH or organic acid content pg; go; on dry matter intake of'rlmlinants are few. munch (1959) in a lIO-day trial compared the dry matter intakes and milk production of dairy cows fed either grass silage or grass silage treated with sodium hydroxide to increase the pH to approxi- mately that of hay. Average pH of the treated silage was 5.85. Dry matter intakes of the groups averaged 2.17 lb. /100 lb. body weight daily for the control group and 2.21 for the experimental group. The difference was not statistically significant. 15 Acetic, prepionic or lactic acids as the free acid or salt have been fed in a number of trials to ovines (Liebscher, 1952; Bentley, gt 31., 1951;, 1956; Goetsch and Pritchard, 1958; Essig, gt 'l_;a1__., 1959; Matrone, gt gay, 1959) and bovines (schmidt and Schultz, 1958; Martin,_ gt _a_1_., 19593 Ellery, gt 2%., 1961). In most of these studies, however, the treatment effect on roughage consumption was not of primary interest. _ Lactic acid when fed to cows at the rate of 2.8 lb. daily, depressed hay intake (Mary, gt gt. , 1961) . It has also been reported that acetic acid depressed forage intake of ruminants (Heiske and ‘ Flechsig, 1889; Liebscher, 1952). Feeding sodium propionate to lactating cows, however, resulted in no significant effect on hay consumption (Schmidt and Schultz, 1958) . One-half pound of. sodium propionate and 17.5 lb. grain were fed each animal daily in this study. Bentley, gt 5.1__. (1951;) found that feeding lactic acid or an acetic-propionic mixture did not reduce hay consumption of growing limbs. The effect of pH or specific acid content of silage, therefore, on dry matter intake of silage-fed animals cannot be clearly stated from these trials. Nevertheless, Hillman's study (1959) indicates that the factor responsible for reduced dry matter consumption is not pH 29; gg. Sane unidentified factor, however, present in silage effluent reduced the dry matter intake of hay-fed animals when this liquid was added to the roughage, and a similar response was obtained when the effluent was introduced into the rumen via fistula (Anon. 1959) . 16 Investigations concerning the effect of silage acids on the metabo- lism and alkali reserve of ruminants have generally been. confined to LIN. silage. kperiments reviewed by Schoch (1957) migrate no ' significant effect of feeding silage stored with no preservative or with f sugar on the alkali reserve of the animal. Piskunov (1958) ther, in casparing the effects of grass and silage ont-month-old calves, found that silage-fed animals had faster heart and respiratory rates, higher arterial blood pressures and alkali reserves, stronger heart sounds, lower urinary mania contents and less well-calcified bone. Factors Influencing the Dry Matter Intake of Rminants Ametite: Defined and Quantitated ' The initial problem encountered in a survey of the literature pertinent to appetite is one of semantics. Physiological usage of the terms associated with this phenomenon have been reviewed by * Boussay, gt gl_. (1955) and include in part; hunger -- a physiological state resulting frat food privation ofa specific or general type and abolished by ingestion of these foods. Sensations of hunger give rise to appetite and ingestion'of food, which suppresses appetitive behavior and the desire for food ceases, resulting in a state of satiety or physiologic anorexia. I The concern here is with feed factors determining satiety, and the physiological mechanisms responsible for this cessation of eating. A number of suggestions have been advanced concerning the criteria to be used in determining the filling effect or satiety value of a food for ruminants . Kruger and Muller (1955) postulated that the feeling 17 of satiety in cattle was controlled primarily by the filling of the reticulo-rmnen and hence, the animal‘s requiresent for satiety should bebased on the volume eaten. Others (Dodsworth and (mull, 1955; Kruger and Schulze, 1956, 19583 Kefford, 1958) generally agree with H this opinion. The problem, however, is the definition of the factors constituting bulk, which will be discussed in a later section. Kruger and Schulze (1956, 1958) attempted to calculate the satiety value of foodstuffs using the dry weight, volume and moisture content. Hesselbarth (1951;) and Kruger and Schulze (1956) have suggested the use of eating rate as a measure of appetite of the cow. This is apparently intended to apply to total wet weight of feed construed and in this case, would be consistent with the results of . eating rates and dry matter intakes of animals fed various forages (Harshbarger, l9lt9; Stallcup, gt g” 1959) . Hancock (1955), how- ever, in reviewing the gazing behavior of cattle, found little or no correlation between grazing time and dry matter intake. Kefford (1958) considers in addition to the volume of the reticulo- rumen, the rate of passage of feedstuffs when he suggests that "appetite of a ruminant is principally a function of the amount of material already in the rumen, and can be measured by the inverse half-life of food material in the rumen." 8voboda (1957) has dis- tinguished between physiological repletion -- when the animal's nutritional reqhirusents are satisfied, and mechanical repletion -- the degree of satiation appropriate with regard to bulk of the feed. is X It is'the opinion of several (Murray, 1926; Huffman, 1959, 19591:; Fissmer, 19M; Makela, 1956) that the dry matter consumed is the best criterion for expressing the effect of a feed on the satiation of the h. cow. 1‘ Factors affecting the dry matter intake of mminants have 1 recently been reviewed by Mahala (1956) , Rim (1958) and Hillmsn (1959) . These reports plus those of Huffman (1939) , Mather (1959) and. Mcclfllough (1959) suggest that feed intake is influenced by the animal's size, 1 3? age, health, inheritance, body condition, exercise, milk production, growth, stage of gestation, effective capacity, and psychology; environ- mental factors such as water availability, frequency of feeding, amount of grain fed, atmospheric conditions, previous feeding history; feed factors such as bulk and. balance of the ration, plant species and stage of maturity, storage methods, feed digestibility, palatability and rate of passage, toxic compounds and deficiency of specific . nutrients. V Primary concern in this section will be the effect of these factors on physiological processes which are possibly involved in the ruminant's regulation of dry matter intake. Palatability: Snell and Taste Differences in dry matter intake of ruminants offered various forages are frequently explained on the basis of palatability. This h The author concurs. This explains the title of this section. 19 nebulous term, palatability, is defined (Anon, 1955) as "agreeable to the taste; savory; hence acceptable." Thus palatability is a relation- ship between factors in both the feed and the animal. Gordon (1957) has essentially restated the previous definition in pointing out that palatability is the "sum of the factors which Operate to determine whether and to what degree a food is attractive to an animal" and that palatability may be affected by hunger and appetite. Pratt, 93': _a_._l_!. (1958) have suggested that the "absolute palatability" of a feed may be determined when only one feed is offered to an animal and the intake determined. To explain differences in dry matter intakes on the basis of. palatability, therefore, is no more than an admission that a difference exists, giving no reason therefor. Palatability is thus a relative tem and is determined experimentally by offering simultaneously to the animal all of the forages to be compared and determining the intake of each (Huffman, 1959) . Appetite, as stated previously, is determined experimentele by offering the animal only one feed or ration and detennining dry matter intake. ‘ Taste is commonly employed to describe the collective sensations of. smell, taste, texture and a multitude of factors that can contribute to the stimulation that occurs with the ingestion or food (Kare, 1959) . Techniques used in the study of the physiology of taste have been reviewed by Beidler (1957) but are of little value in determining the affect of taste on feed intake. Kare (1959), in preference trials, found that calves preferred a 1% sucrose solution but failed to 20 discriminate between sugars on the basis of sweetness as hmnans would. Inan unpublished study cited by Kare (1959), Kareem! saith offered - growing heifers either "candy-coated hay pellets" or unicoated pellets. Initially the experimental groups consumed more than the controls but intake was essentially the same between groups at the end of two weeks. In preference trials, the coated pellet was preferred. . Tuckerman (1891) in a study of the number of taste buds of the circumvallate papillae in 13 species, found that the prongbuck, the only ruminant studies, averaged 108,000 of these structures. Next - in total number was the dog with 8,000 taste buds. Kare (1959) has reported that the ruminant has 10-20 thousand taste buds ccmipared with only a few thousand for man. In the rat, however, the number of taste buds is poorly correlated with taste discrimination (fifafmann, 1952) . fiqmriments concerning the sense of smell in relation to feed intake in ruminants are limited. Tribe (1919) reported the renoval of the olfactory lobes in a group of sheep. when a control group and the experimental group were offered fresh-cut and 2-day-old grass, the control group ate more of the fresh material whereas the experimental group ate equal amounts of both samples. Tribe concluded that the sense of smell was only of supplanentary importance in influencing the food selection of grazing sheep. Bulk Throughout the literature pertinent to the control of feed intake in the Imminent, there is frequent direct or tacit suggestion that 21 min a feed controls the amount- eaten by these animals That is, the animal eats until it is full and this capacityislimited by the gastro-a _ intestinal tract or available space in the abdaninal cavity. An excellent review dealingwith bulk in the nutrition of farm animals and the capacities of the gastrointestinal tracts of the heme has recently been published by Makela (1956) . Todefine what constitutes bulk in a feed is difficult, and the“ term has been used with varied meanings. These problems have been dis- cussed byusynard and noosli (1956) . or the factors investigated which possibly contribute to‘bulk, it is appropriate to consider first the wet weight of the ration. As was mentioned earlier, Kruger and Schulze (1956, 1958) derived equations based on dry weight, volume and moisture content of the feed to calculate the satiety value of a feedstuff. These workers calculated setiety units (3. U./kg. feed) of 0. 9-1. 8 for silage and green feeds, 7-12 f0r coarse hays, 8.25 for alfalfa.hay and 5.17 for oats. Capacity of'young cows was fbund to be from 100-150 S.U.'s. Others also feel that water contributes to the bulk of -‘ the ration. The experiments of Dodsworth and cempbell (1952, 1955) and Dodsworth (195h), cited previously, indicate that water content of silage influences the dry matter intake of animals fed this product. Evidence was also cited which demonstrated that water content could not explain the decreased dry matter intake (Thames, 25 al., 1961b) and that cows fed wetted hey did not reduce dry matter intake (Hillman, 1959) . 22 Duckworth and Shirlaw . (1958) fed groups of four Ayrshire heifers either dried or fresh grass taken frail thesame‘plot daily. ' Average . daily consumption peranimal ona wet basis was 35.2 and7l.5 lb. for dried and fresh grass, respectively. Average daily drymatter intake of both groups was 17.8 lb. / animal. Yet these workers suggested that wet matter intake controls appetite, basing this conclusion on the ' high correlation between daily dry matter percentage of the fresh grass and dry matter intake on different days. ’ rissmer (19111) determined the dry matter intake of dairy cows fed ad libitum fresh vetch (11.6% dry matter) and lupine (8.15% dry matter) or clover hay. Data presented}. indicate that moisture content had no effect on dry matter intake. Similar results (airman, 23; 31., 1957; Forman, 3]; 3,, 1958) have been cited previously. PoiJarvi (1918) found that dry matter intake decreased when ruminants were fed roots and potatoes and concluded that cellular water exerted a filling effect. The emeriments of Makela (1956) confirmed these results but the author attributed the intake difference to the greater rumination time required for roots. Evidence that large mounts of water can be tolerated by the dairy cow is found in the report of Thanpson, _.e_t_~ 314 (l9h9) which documents an average daily water intake of 350 1b. for a Jersey cow inlan ambient temperature of 100° 3‘. Urinary output was 275 lb. /dsy. Since cows do not eat to a constant total weight of feed over a range of feeds, others have suggested (Kuhn,'18733 Pott, 190%) that dry matter content is the best measure of bulk in a feed. Ietnaann 23 (1911-1) postulated that the mmt of indigestible organic matter (ballast) in the feed determined how much the Cow would eat . This worker calculated that a 500 kg. cow should be satisfied after eating It.) kg. of ballast. rissmer (1911-1) and Makela (1956) , however, were unable to experimentally confirm Inhnann's postulate. These workers found in a lumber of trials using various foods that the amt of ballast eaten was not a constant but depended on the ballast content of the feed under consideration- Dry matter intake per 100 lb. body weiyit was more stable than the folmer. Jones (1952) postulated that the fiber content or grass and clover hay limited the amount eaten each day, implying that this was a measure of bulk. Duckworth and Shirlaw (1958) drew similar conclusions from one of their experiments with cattle fed fresh grass. Blaxter at al. (1956) , however, feel that neither dry matter content nor amount of indigestible residues produced by a feed per unit time are satisfactory measures of satiety value since these criteria do not measure the distension of the digestive tract. In these experiments, attempts to correlate satiety value of feeds with some factor which measures bulk have been cited. It is apparent, however, that rate of passage of a food through the gastro- intestinal tract possibly influences the amount consumed. Although factors constituting bulk possibly influence rate of passage, the latter is discussed separately for convenience. 21+ 15 Techniques used in studies concerning passage rate of indigestible Rate of Passage and mgestibili feed residues or dry matter through the digestive tract are varied, but are of three general types. These methods are slaughter of the animal post aenam and determination of dry matter content of the various gastrointestinal organs (Ewing and wright, 1918, Makela, 1956) , detemination of dry matter disappearance or flow true or through a fistulated portion of the digestive tract (Chance, .932 elm 1953; Btallcup, _e_t al., 1956) or the measuranent of the passage rate of stained hay. particles (Belch, 1950; Bleacher, _e_t g“ 1956; Castle, 1956) or other markers (Lambourne, 1957) through the animal. The latter has also been used in rmenectomized animals (Piana, 1952) . Experiments surveyed initially include those in which one forage was fed at different levels or in different physical forms. Sub- sequently, those comparing different forages will be cited. In one of the early experiments (Porter, 33-, _a_l_., 1953) in which ground and. pelleted alfalfa hay was compared with ground, chopped or long has; for lactating dairy cows, no significant differences in dry matter intakes were found in one trial and a reduced intake of pellets was reported in the second trial. This reduction was attributed 5 Since experiments cited subsequently utilize cattle, sheep and goats, it should be pointed out that the possibility of species differences in digestibility of silage (Cipolloni, 33; al., 1951) and. corn silage and hay (Watson, et al., 19168) exist. Others report no species differences in the digestibility of grass silage (Sears, _e_t al., l9h2) or hay and grass silage (Piatkowski, 1958) . 25 to the hardness of the pellets. More recently, however, lactating cows were found (Ronning, _e__t _;a_l_.., 1959) to. consume more. dry matter from 5 ground and pelleted alfalfa hay than those fed chopped alfalfa hay. . Similar observations have been made with sheep (Meyer, _e_t __a_l., 1959a, 1959b) . Chopping green corn or cats and vetch has been found to result in marked increases in dry matter intake of pregnant heifers (Bainter and vitai, 1956)- . Esperimental attempts to explain the observed increase in dry matter intake of animals fed ground and pelleted hay are limited. Meyer, gt g_l__. (1959b) found that the increase was due to fine grinding and not the pelleting process. Using stained hay as a marker, Blaxter, 93 g. (1956) found that the passage time of the indigestible residues of ground and pelleted hay was markedly less than that of long hay fed to sheep. Meyer _e_t _a_l_. (1959a) obtained ' similar results by slaughtering sheep at various times after feeding and determining organic matter contents of the various parts of the digestive tract. Belch (1950) , however, found that the excretion time of indigestible residues was longer for cows fed ground hay than those fed long hay. then ground and long hay were fed together in this study, the residues of the former appeared in the feces more rapidly. Although the net energies of ground and pelleted hay and long hay have been found to be the same (Blaxter and Graham, 1956; Meyer, _e_t _e__lu 1959a), the apparent digestibility of dry matter was significantly depressed by grinding and pelleting in the study of Blaxter and Graham 26 (1956) but this treatment resulted in no siglificant differences in, organic matter or holocellulose digestibility in the trial. of Meyer, .93 £- (3,5992 ' A . . Blaxter, _e__t g. (1956) fed sheep either 600, 1200 or 1500 pg. of hay daily. When the hay was finely ground and pelleted there were ’ marked decreases in dry matter digestibility and meanretention time of the indigestible residues in the digestive tract as the level of feeding increased. with long hay, however, the dry matter digestibility did not differ sigiiricantly as level of feeding increased, but” the retention time again decreased in this case. Others havereported . only slight changes in digestibility of all-forage rations by ruminants as level of feeding. increased (amend, 9:9 395-: 19553 Mahala, 1956; - Andersen, _e_t_ 5., 1959). Inerpcriments in which only long hay was fed to cows (Makela, 1956) , the level of dry matter intake was shown to have a marked effect on passage rate. The mean retention time of a dry matter point (calculated by dividing the dry matter contents in the reticulo-mmen by the daily intake of dry matter following a constant daily feed intake) in the reticulo-rumen was found to be approximately 1 day with cows fed :93 libitum and 2-3 days when the animals were fed one- third this amount. These observations were confirmed in a later study (Paloheimo and Makela, 1959) and similar results have been obtained (Lunbourne, 1957) with sheep fed a variety of forages 9g libitum. Ewing and wright (1918) found that increasing the level of intake or corn silage fed ,to steers decreased the passage time of indigestible residues 27 through the alimentary tract. Balch (1950) obtained converse results with cows fed solely long hay. Further experiments of Belch (1958) concerning‘the‘dry matter disappearance from the rumen of cattle fed various rations are inconclusive . 7 when concentrates are added to the A, ration, the passage rate of indigestible residues of concentrates is faster than that of hay (Burroughs, 33 2.1... 19%; Belch, 1950). In the experiment of Ewing and wright (l918) cited previously, the addition of cottonseed meal to the highest level of corn silage fed, decreased the passage time of the indigestible residues of the total ration. 1n cows fed high levels of concentrates (1:1 concentrate to hay ratio), there was no apparent relationship between retention time and dry matter intake (Paloheimo and Makela, 1959) . Castle (1956) fed MOO g. concentrates daily and meadow hay g libitum to goats and found a negative correlation which was Just significant between feed intake and mean retention time. when an individual ate more, however, there was no tendency for the mean retention time to be decreased. Marked differences in passage rate of indigestible feed residues are observed with various roughages. Stallcup, _e_t g. (1956) fed - steers free choice hays of varying lignin content and found that dry matter intake and disappearance (was greatest for the hays of lowest lignin content. Lambourne (1957) found that excretion of markers was slower for sheep eating hay than for pasture- fed animals while intake of dry matter was greater for the latter group . 28 Factors other than level of feeding and. type of ferage appear to _ alter passage rate. tBalch (1958) reported that dry matter disappearance from the rumen of cattle fed various levels of different rations was most rapid during eating. The feeding of low levels of aureanycin to mature'rmninants increased (Chance, _e_t al., 1955) slightly-the rate of disappearance of’dry'matter from the ranch.) It is well-established that feeding aureanycin to young dairy calves increases feed intake (reviewed by Lassiter, 1955). That this can be related to passage rate of indigestible feed residues through the digestive tract has not been (shown. , Although evidence has been cited which indicates a correlation between rate of passage, digestibility (of ground forages), and level of intake under certain experimental conditions, the causal relation- ships remain obscure. Since correlation involves no assmnptions regarding the nature of the relationship, it is not surprising that converse conclusions have been drawn from similar data. Thus, in regard to the voluntary consumption of forage dry matter, the question whether dry matter intake controls rate» of passage or rate of passage limits dry matter intakaz‘is unanswered. Mrs-Gastrointestinal Factors Consideration of factors influencing dry nutter intake has been, to this point, given to characteristics of the feed, gastrointestinal phenomena or interactions of the two. Evidence cited in a subsequent section concerning non-nnninant appetite regulation deconstrates that < _ 29. . centers in the hypothalamus are involved in thisregulation. _That the central nervous system is also involved in the ruminant "s regulation of feed intake has been dmnonstrated . ingthe pioneer experiments of. ”Larsson (1951;) . wWorking with sheep and goats, Larsson found that electrical stimulation ofthe hypothalamus and the medulla, and intra-hypothalamic injections of various solutions resulted in hyperphagia. Frequently, a second stimlation of hypothalamic points previously causing feed (ingestion resulted in mination, and the author postulated that rumination could possibly be involved in regulating feed intake. Medullary stinmlation, in contrast to hypothalamic stimlation, resulted in hyperphagia and perverse appetite; the animals accepted poor quality feed even when contaminated with feces and urine. Blood sugar changes could not be referred to mperphagia and. rumination. Others have been concerned with the relationship between rumination and feed intake. Hancock (1955) reports a positive correlation between rumination time and dry matter intake with the shape of the curve depending on the crude fiber content of the grass. McCullough (1956) found a gross correlation of 0.168. between dry matter intake and ruminating time. Duckworth and Shirlaw (1958) found in comparison of long versus chopped silage that cows fed the unchopped product ate significantly more dry matter but spent no more time ruminating than the group fed chopped silage. In canparisons of long, chopped and ground hay (Gordon, 1958b), however, animals ruminated more on chopped hay than long hay but less than either of these when the hay was ground to a meal. Gordon (1958a) reported no relation between times 50 of mination during the day and times of eating. Morever, it has been noted (Mead and Goes, 1936) that heifers reared on a roughage-free diet continued to ingest concentrate even though rumination occurred at irregular and infrequent intervals. '- The availability of blood glucose has been postulated (Mar, 1957a) to control feed intake in non-ruminants. This metabolite, how- ever, appears to have no controlling influence on the i In'pothalamic feed regulatory centers in the ruminant. Manning, _e_t g. (1.959) infused large doses of glucose into the Jugular vein of sheep, increasing blood glucose from 140.0 mg.$ to.- 205 .0 mg.$ by One hour post-indection. At this time the animals were fed. There was no significant difference in feed consumption between the experimental group . and the saline- injected controls. Administration of 3.8 lb. of glucose to a steer ~ via stomach tube gave only a slight rise in blood sugar (Dougherty, 212 5:9, 1956) . Both sheep (Jasper, 1953b) and cows (deeper, 1953a) are more resistant to insulin injections than non-ruminants. Although hypoglycemic symptoms were produced in both sheep and cattle, it was difficult to reduce the blood glucose level of the ewe below 5 mg.$ . It will be shown later that non-ruminant species adJust caloric intake to expenditure over long periods of time. But only Crasemann (1953) has suggested that ruminants strive for an energy intake to supply requirements for maintenance and performance. According to Crampton (1957) , however, there is no evidence that the amount of forage eaten by an animal depends on the gross energy content. It is the opinion of Blaxter (1950) that ruminants do not regulate appetite 51 according to energy requirements. Although silage dry matter appeared to be utilized mOre efficiently for milk production in several studies _ (Stone, _e_t g. , 19593 Keyes and anith, 1955: Nicholson and Parent, 1957) , it has not been suggested that this explains the reduced dry matter intake of silage-fed cows. ' This section has been concerned primarily with the. relationship between certain physiological mechanisms and feed intake of the ruminant. ‘ Maw factors, however, have not been included. f For exanple,‘ decreased feed intakes result from excessive ambient temperature (Bagsdale, gt 3;. , 19503 Findlay, 1958) , deficiency of required nutrients such as protein (Everett, gt 51.31958), phosphorus (Hufman, 1933) or cobalt (Baltzer, 93 al., l9hl) and excessive amounts of nutrients such ascobalt (Ely, 53 g. , l9h8) . Others could be mentioned. The effect of. nutrient excesses or deficiencies on voluntary feed intake has been reviewed by Iopkovsky (19%. 1955) . Appetitecontrol in Non-Ruminants Early theories concerning appetite control have been adequately reviewed (Carlson, 1916; Miner, 1955; Hoelzel, 1957) and will be treated only briefly here. The remainder is concerned with more recent work concerning the control of feed intake (reviewed by Lepkovsky, 19148; liner, 1955; layer, 1957a, 1957b; Grossman, 1958; Morrison, 1959; Anand, 1961) . ' Carlson (1916) in a book concerning the control of hunger, grouped the early theories concerning the cause of hunger. These attributed hunger to (l) sensations of peripheral origin, mainly in O .I. .L / _ "Ls I... vi 32 the digestive tract, (2) direct stimulation of a hypothetical hunger center in” the brain by the blood or changes in the metabolism of. the center itself -- a central origin and (3) both of the above -- a general sensation. mthalgic Centers negating Feed Intake Experimental demonstration that centers in the brain regulated feed intake was first made by Hetherington and Benson (1939, 19110, 19112) . These workers found that discrete lesions in the ventro-medial nucleus of the? hypothalamus of rats led to a marked increase in food intake, characterized by more frequent eating of smaller meals than non-operated controls. Results of obstacle tests (Miller, 33; 3., 1950) showed that hypothalamic hyperphagia was not the result of an increased drive for food but a defect in the satiety mechanism. This has been confirmed by other workers (Anliker and Mayer, 1956; Anand and Brobeck, 1951b) . The animal markedly increases. food intake inmediately after the lesion is placed but decreases in intensity until the body weight reaches a new but higher relatively constant level. At this stage food intake falls to a level slightly above that of normal animals (Morrison, 1959). When lesions were made in the lateral hypothalamic area, cats and rats danonstrated a non-reversible aphagia (Anand and Brobeck, 1951a) . This appears to be a feeding center. It has been shown recently, how- ever,that sane rats "escape" from lesions in this area and resume eating (Mayer and Morrison, 1958) . Discussion .of the locations of these lesions has been presented by Morrison, _e_t ...-.39. (1958) and will not be ' ‘ . (I II. 33 discussedhere since recent evidence (Larsson, 19310 indicates that centers (in other areas of the brain are involved in regulating feed intake. Nevertheless, it has been conclusively demonstrated that satiety and feeding centers are present in the hypothalamus). It has been pointed out by Morrison (1959) that amr stable control systm must have (a) a sensory input, (b) a central integrating organ- ization, (c) an effector or response mechanism and (d) a feed-back . device. Clearly, at least two of the central integrating areas con- cerning feed intake have been demonstrated. Other parts of the control system remain to be established with certainty. Several proposals have been made concdrning the sensory input to these regulatory centers and will be discussed separately. Gastric Fill and Contractions ’ The first hypothesis concerning hunger to receive experimental support was that of Cannon and washburn (1912) who attributed hunger to contractions of the stcmach, but explained that the total amount of food eaten was not explained by these contractions. This result was confirmed by Carlson (1916) who found that the intensity of hunger contractions increased in fasting. Hoelzel (1957) , however, in experi- ments with himself, noted that hunger contractions had decreased or disappeared by the fifth day of a 26-day fast. Further, filling the stasach following a fast did not satisfy Hoelzel, who was still hungry but without room for more food. Other evidence which did not support . 3h the theory of Cannon and Vashburn were reports that denervation or operative removal of the stomach did not abolish hunger (Grossman and Stein, 19h8) and that appetite was preserved even after gastrectaw (Sherrington, 1900). _ Dilution of the ration with water or kaolin has been shown (Adolph, 19%?) to result in an increase in feed intake to keep con- stant the caloric intake in rats. Dilution of the diet with sawdust , resulted in an increased feed intake in rabbits (Abgarowicz, 1911-8) and pigs (soldstein, 1950). Introduction of celluflour into the. stomach of the dog before feeding only reduced oral feed intake when large amounts of the inert substance were placed in this organ (Share, at 51.. , '1952) . Glucostatic Theggy Evidence supporting the glucostatic theory of appetite control (her, 95 _;_a_'.|_..,-1951) has recently been reviewed by Mayer (1957a, 1957b, 1958) and the hypothesis restated with modifications. Mayer reasoned that the satiety center of the Mpothalmaus must be sensitive to glucose since it was an essential to the central nervous system and further, .boch'r reserves of protein and fat were proportionately large in relation to carbohydrate stores. The postulate as originally stated (Mayer, _e__t 5:1. , 1951) was that these brain centers were glucoreceptors and were sensitive to variations in (absolute) blood sugar levels. In later reports (Mayer, 1955, 1957b) , this was changed to the availability of blood glucose to the cell as determined by arterio-venous difference 35 (A- glucose). The correlation of amaL‘LA- glucose values with hunger was danonstrated by this map (Van Itmie, gt a_1_., l953)and confirmed by Stunkard and Wolff (1956,1958) and Stunkard, 333 51. (1955). Other workers found no correlation between low A -g1ucose and hungerCBernstein and Grossman, 1956; Fryer, .93. al., 1955a, 1955b). 'Protanine insulin has been "shown to stimulate the food intake of rats (Macm, _e_t 31. , 1910) but the hypoglycemic canpound, tolbutamide, failed to increase food in- take, and insulin reduced feed intake in bahyfpigs (Pekas, gt 5.1., 1959). Additional evidence to support the glucostatic theory was the discovery that injection of goldthioglucose, but not other gold canpounds ‘ produced permanent obesity in lab animals. due to hyperphagia (Holliiield‘, _e__t £1. , 1955) . Since mice with goldthioglucose lesions ate more . frequently than normal mice (Anliker and Meyer, 1956) , the authors postulated that this ventranedial area acted to brake a constantly active feeding center which is ostensibly located in the'rlateral hypo- thalamus. Histological studies (cited by Mayer, 1958) indicate that cells,taking up goldthioglucose are not limited to a particular area or the hypothalamus but are of greater density in the ventranedial area. 'Following the. report of Forssberg and Larsson (1951+) that 39F uptake by the ventranedial hypothalamus was greater in hungry than in fed'rats' and greater in this area than (in other hypothalamic areas, Mayer (1958) has modified the glucostatic theory, postulating that "the influence of: the metabolic state on feeding behavior and its role in regulating food intake (are) mediated through the rate of passage of glucose (or of ions associated with the passage of glucose, e.g. , potassium and glucose phosphate) into the cells of the ventrmedial hypothalamic area." Mayer, in slnmnarizing his current position, states 36 ". . . there are a great many physiologic and psychologic factors influ- encing food intake; these may intervene at several levels in the central nervous system, in particular the lateral hypothalamic area, the thalamus, the frontal lobes and other parts of the brain cortex. Among these factors, the metabolic state (of the organism is of particular importance; it is the factor which "regulates" food intake, i.e, which adausts intake to output. At least part of the mode of action of this factor is through a glucostatic mechanism based on the ventranedial ‘hypothalamic area. While a part of the awareness of hunger is' through awareness of gastric contractions, (which in turn may be controlled in;. part by central deprivation) it appears that it) is not through activation of hunger as such but through the application of a satiety brake that this ventranedial glucostatic mechanism operates." Thermostatic 'l‘heo It was proposed in 1951 (Strang and McClugage) that the specific dynamic action of food influenced feed intake. Later this suggehtion was tested experimentally and made the basis of a hypothesis concerning regulation of food intake (Brobeck, 191:8, 1957a). Brobeck (191(8) observed that rats exposed to an ambient temperature of 65-760 F increased feed intake and gained weight, whereas above 92° F feed intake decreased, water intake increased and body weight declined. The author postulated that the amount of food eaten was in part determined by the animal's ability to dissipate the heat of food metabolism (sm) . 37 Evidence interpreted as confirming this hypothesis has been pre- . sented for laboratory animals (Btrcninger, 93; g. , 1953; Btrcninger and Brobeck, 1955) and man (Passmore and Ritchie, 1957) . Kennedy (1955) however, in testing this hypothesis, found in longer trials that normal rats and those with hypothalamic lesions lost weight when (transferred to 75°, F ambient temperature but gradually recovered the weight lost within 60 days. then placed in 3&0 1' cold roads the animals increased feed intake but also lost weight. It was further demonstrated that the lactating rat increased feed intake markedly and even more when the diet was diluted with kaolin. These results were deemed incmpatible with Brobeck's thermostatic hypothesis. Brobeck (1957a) has emphasized the possibility of multiple factor control of feed intake, , of which taperature regulation is only a part. Both the ’glucostatic and themostatic theories have been criticized (Hervey, 1959) on the grounds that both control (feedback) clenents, viz. , glucose and temperature, are subject to known physiological . regulation of their own. _Lipostatic Theory Kennedy observed that growing rats with Impothalamic lesions (1956) and similarly treated lactating rate (1955) did not'beccme obese. Since hypothalamic lesions do not cause infinite increases in body weight but stabilize at some higher level, Kennedy (1953) suggested that the hypothalmic satiety mechanism was (concerned only in preventing a surplus energy intake and hence, to prevent the accumulation of fat by long-term regulation of the intake of food. 38 No explanation of how this was carried out was proposed. Kennedy (1956) _accedes ”that other adjustments are carried out through different mechanisms. It has been suggested (Mayer, 33 5,1. , 1951; l’assmore, 1958) (that a certain mininnm level of energy expenditure is necessary for the control mechanism to function effectively to maintain energy equilib- rium in the adult animal. Since glucose and fat are involved in feed intake theories, it should be mentioned that Mellinkoff, 33 2.1." (1956) found that a reciprocal relationship between serum amino acid concentration and subjective estimation of appetite existed in the human. Intravenous infusion of casein hydrolysate and glucose decreased subjective hunger but casein hydrolysate ministration alone pranpted a decrease ‘ in both blood glucose level and appetite. Criticism of these proposals concerning regulation of feed intake has been presented. In addition, these theories do not explain several observations such as the reduction of feed intake dam to water deprivation (Lepkorvsky, _e__t 51. , 1957) , testosterone injections (Kochakian and webster, 1958) or benzedrine (Pelner, 1915) and amphetamine canpounds (Cass, 1959) given orally to humans. maximum. mocsmm Four continuous dd libitum feeding trials were conducted in the fall-winter seasons of 1957-58 and l958~59 with growing Holstein heifers fed only alfalfa silage or hay cut concurrently from the same field. Various forage alterations to be described subsequently were made in an attempt to elucidate the reasons for observed differences in dry matter intake of dairy heifers fed solely alfalfa hay or silage. In all. trials, the animals were housed in the Beebersheimer Barn at the Michigan State University Experiment Station and were not removed from their stanchions during this time except for liveweight measurements. The rations were offered in two portions, at approxi- mately 7:00 AJI. and 5:00 P.1d, in sufficient quantity to allow approximately 10$ weighback prior to the afternoon feeding. All. forage offered and orts were weighed to the nearest 0.1 lb. on a Hansen ' milk scale. A sodium chloride-cobalt-iOdine salt mixture was offered free choice on alternate We. Liveweight measurements were made at the beginning of each experiment, at monthly intervals thereafter, and at the termination of each trial. These observations represent a 3-day average of readings made on a dial Toledo platfom scale graduated in 2 lb. increments. The average of the initial and final liveweights for each experimental period were used in calculation of dry matter consumption per 100 1b. liveweight. Response criteria for all. experiments were average daily gain, average daily dry matter intake and the average daily dry matter intake per loo lb. liveweight. These data were subjected to the analysis 39 9.. we» ‘ :r “ . to of variance . (Snedecor, 1956) and further tested in the event of significant differences using Hartley's sequential'method outlined by Snedecor (1956), to obtain individual differences among means. Trial 1. Animal response to alfalfa silages or hay fed g libitum Twenty- four heifers averaging 671+ 1b . liveweight were divided into three canparahle groups and offered only alfalfa hay (Group 1) , wilted alfalfa silage (Group 2) or direct-cut alfalfa silage (Cheap 5) free choice to establish dry matter intake differences among the forages. The trial was started October 5, 1957 and continued for h weekly periods. Alternate sections of a uniform field of alfalfa in approximately one-fourth bloan were cut during the period June lit-18 for the two silages and hay. One lot of alfalfa was wilted to approximately 75$ moisture prior to ensiling on June 18. “Another lot was direct-cut with . a lacerator and ensiled on June 11+. No preservative was used in either silage. Bay was field-curedwith no rain danage. The silages were stored in stack silos constructed as outlined by Purdue workers (Hill, _e_t 3d,, 1957).. Stacks-were made on a concrete slab using a flight elevator and shaped and packed by two men. Stack dimensions were approximately 1% ft. width, 8 ft. height (before settling) and he ft. length. Both were covered with 6 mil polyethy- lene plastic 6, the edges of which were weighted with logs and soil to effect a seal. After settling, the slack plastic was ranoved from silo 2 (direct-cut) but this was not done with 3116 1 (wilted). Holes 1” " 6 Supplied by The Visking Ccmpany, Terre Haute, Indiana. hl which developed in the plastic were patched with pressure tape. Rats made numerous holes in both plastic covers during the winter months. Both silages were szed at weekly intervals during. the feeding trial for dry'matter and/or proximate analyses using standard A.O.A.C. methods (1955) and pH determinations using fluid expressed frail the 3.11. silage. Composite weighback samples by treatments were taken weekly for dry matter determinations necessary for the calculation of dry matter intake. Bay was sampled less frequently and canposited for proximate analysis. Trial 2. Animal response to adding acid, Silo-Joy or ground hay to , . forages. . Following the preliminary trial (Trial 1) in which dry matter intakes of heifers fed the silages were lower than hay-fed animals, an additional experiment was planned in an attempt to determine the reason( s) for this observation. Tested in this trial were (the possibilities that changing the flavor or increasing the dry matter content of silage would improve dry matter consumption, and that lowering the pH of by to approximately that of silage would reduce dry nutter intake. Animals in each group remained on the same forage consumed in Trial 1, but each group was subdivided to give canparable average dry matter intakes per 1.00 lb. liveweiglt and half assigned to the following treatments: Group 1A, bar with 200 ml. of 2.8 N. hydrochloric acid added per 1.0 lb. hay; Group 2A, wilted silage mixed with 30 m1. 329‘. “t Ag; he of a 7.6$ (w/v) suspension of Silo-Joy 7; Group 5A, direct-icut silage with 1.1 lb. ground alfalfa hay (frcn the same lot fed Groups 1 and 1A) added per 10 lb. silage. All additions were made at the time of feeding and well mixed before placing before the animals. The forages described for Trial 1 were used during the present trial. Forages and arts were sampled during each weekly period for dry matter and/or proximate analysis. Due to rapid surface spoilage of the silages, the wilted silage fed to, Groups 2 and 2A was depleted in 2 weeks and the direct-cut silage was exhausted at the end of 5 weeks. Trial 5. Animal response to adding water to silage when fed Since water content of the forage ensiled in Trial 1 resulted in different types of silage fermentation and differences in dry matter consumption by daily heifers, an additional study was planned to determine the effect of water addition on dry matter intake when added to a given silage at the time or feeding. Twenty-one heifers averaging 775 lb. liveweight were divided into three equal groups as to numbers and average liveweight and offered free choice only wilted alfalfa silage (Group 1), the suns silage with water added at the time of feeding to increase theimoisture content by 5; (Group 2) and 10$ (Group 3). The trial was started November ll, 1958 and continued for 8 weekly periods. 7 Anifeed-Dribase Silo-Joy Flavorstat, containing NaCl, tricalcium phosphate, cinnamon, vanillin and other spice extracts, metmrl salicylate, butylated hydrmqr-toluene, arabic, citric acid, chlorophyll. Supplied by the Flavor Corporation of Inscrica, Chicago, Illinois . 1+3 Alternate sections of a uniform field of alfalfa in approximately one-fourth blocm were cut on June 5 and field cured for hay. Rain during the curing period amounted to 0.75 in. The renaining forage was cut on June 6, 7 and 9, allowed to wilt to approximately 70$ moisture, field-chopped and blown into a new concrete-stave silo. No preservative was added to the silage. Silage was sampled weekly for dry matter determinations and the mount: of water required to bring the moisture contentslto the desired treatment levels was adjusted for each weekly period. No runoff was observed at any time during the trial frcm any of the silages when water was added at feeding time. Weightbacks were can- posited by treatments daily and subsmnpled for daily dry matter _ determinations. These values were used in the calculation of dairy dry matter intakes of individual animals. Since the same forage was. used in all treatments and only water the variable, proximate composition of the silage was not of interest. The silage remained of excellent quality throughout the trial . ’ Trial h. Animal response to adding acetic acid to hay Results of the previous trials danonstrated that p11 and water 293; 53 were not responsible for the reduced dry matter intakes of cattle fed alfalfa silage . With the possibility existing that a specific chemical entity in silage might be responsible for the appetite- depressing effect, Trial h was designed to test acetic acid, one of the volatile fatty acids present in silage, as a possible. appetite-depressing factor; . M Sixteen heifers averaging 716 lb. liveweight were divided into two ‘ equal groups as to numbers and average liveweight. and offered free choice only alfalfa hay sprinkled with 1800 ml. water per 10 1b. hay prior to feeding or the same hay sprinkled with 18% ml. glacial acetic acid diluted to 1800 ml. with water. The latter gave an acetic acid con- centration of approximately 5% of the dry matter which is in the range of that reported to be in grass silage (Barnett, 195R). Bay was shredded by hand prior to feeding in a metal pan and. the liquids applied with a sprinkling can as the hay was mixed. The alfalfa hay was the lot describ’ed'for Trial 5. The trial was started February 16, 1959 and continued for 28 days. The hay was sampled twice during the h-week period for. dry matter determinations prior to application of the fluid. Weighbacks, for both treatments were canposited and subsampled twice during the same period for similar analysis. These values were used in the calculation of dry matter intakes. RESULTS Trial 1. Animal response to alfalfa silages or hay fed 3g libitum Composition of the forages during Trial 1 (Table 1) indicates a deteri- oration in quality of the wilted silage following opening of the stack as reflected by the increase in pH as the trial progressed. This was undoubtedly due to the exposure of the entire silage surface to air after the stack silos were opened. The wilted silage also decreased markedly in dry matter content during the feeding trial, indicating that microbial activity was taking place. The consistently high pH of the direct-cut silage indicates that this was a poor-quality product . Input estimates of forage and output weights of spoilage and silage fed were made to partition losses of dry matter. Dry matter losses frail seepage, however, were compounded with fermentation losses since no facilities for collection of effluent were available. These data, having no bearing on the objectives of the trial, are sumarized in Appendix Table 1. Results of this preliminary experiment (Table 2) to establish dry matter intake differences among heifers fed the three experimental forages confirmed the findings of several investigators (Bender and Tucker, 1957; Sykes, _e_t 3.3;. , 1955, Keener, gt 3;}, 1958; Lassiter, _e_t al., 1958; McCullough and Neville, 1959; Thomas, £12. 51., 1959) cited previously, viz.., dairy heifers consume less dry matter from silage fed free choice than fran hay made from the same crop .; 7 Hay-fed heifers (Group 1) consumed 2.33 lb. dry matter/loo lb. live- weight/day while intakes of the wilted (Group 2) and direct-cubv.( Group 5) silage groups were 2.01 and 1.60 1b/100 lb. liveweight daily, respectively. #5333 Table 1. Chemical composition of alfalfa ferages utilized in Trial 1 Dry Crude Ether Crude Nitrogen- Ash pH Forage .matter protein extract fiber free extract 5 - - - --- -(¢.-.~of dry matter) ------ fresh 16.6 19.6 2.2 hl.9 27.5 8.9 ‘Hay 8h.2 15.6 1.5 58A 59.0 5.8 6.10 Wilted silage fed Periodl 51.1 18.8 5.2 5h.8 56A; 6.8 n.58 Period 2 25.5; ---- --- ---- ---- Jwgm h.66 Period5 21s?" 17-3 B-h 38.5 53-5 7-7 5-55 Period h 21.7 ---- --- ---- ---- --- 5.20 Average 2500 1800 303 3606 sites 702 how wilted silage orts Period 1 51.2 Period 2 50.1 Period 5 2h.7 Periodli 21+.5 Average 27.6 Direct-cut silage fed (lacerated) 'Periodl 18.2 17.1 5.8 58.1 52.8 8.2 5.28 Period 2 18.1 ---- --- ---- ---- --- 5.h0 Period5 17.8 15.2 1+.o no.0 52.8 7.9 5.56 Period h 17.h ---- --- ---- ---- --- 5.50 Average 17.9 16.2 5.9 59.0 52.8 8.0 5.5% Direct—cut silage orts Period 1 21.1 Period 2 20.8 Period 5 19.h Period h 18.7 Average 20.0 ____.....- ,4- - ...—‘- w '1!" .g‘r Both Groups 1 and 2 consumed significantly (P< 0.01 and P 4 0.05, respectively) more dry matter per 1.00 lb. liveweight than Group 5, but the difference between the former groups was not statistically significant. Table 2. Dry matter consumption and average daily gains in Trial 1 Number ‘ Average Average Average Av. daily Group animals initial daily daily 114 intake/ liveweight gain dry matter 100 lb. intake liveweight (1b.) (1b.) (1b.) (1b.) 1- Kay 8 672 1.69 15.8 2.55 2- wilted silage 8 676 1.29 15.8 2.01 5- Direct-cut silage 8 676 0.09 10.1} 1.60 Std. error of a mean 0.269 0.106 A breakdown of the dry matter intake data by weekly periods (Table 5) revealed a gradual; increase in dry matter intake by the hay-fed heifers as the trial progressed. Conversely, the wilted silage group reached maximum intakes early in the trial, a phenanenon which is difficult to explain since all heifers were fed hay prior to the initiation of the trial and would be expected to reduce intake following such a drastic change in the ration. Dry matter percentage of the wilted silage (Table 1) decreased markedly, however, as the trial progressed and is probably the result of loss of dry (matter by fermentation since no rainfall could reach the covered mass. Alteration of the silage by fermentation could be responsible for the intake decline as the trial progressed. .“ Average daily; .dry matter intakes of individual animals (Appendix Table 2) varied greatly within treatments . Heifer 158 in Group 1, although having the greatest dry matter intake in relation to liveweight in the group, was off feed during the third weekly period, consuming only 56.8. lb. dry matter during the week while her average weekly dry matter intake for the other periods was 79.6 lb. Anifll 608 in Group 2 had the lowest dry matter intake per 100 1b. liveweight of the group. Daring the first week of the trial she consumed 111.5 lb. dry matter but became ill dung the second week of the trial and consumption dropped to 72.1 lb. dry matter. Heifer 609 in Group 5 with the lowest dry matter consumption per 100 1b. liveweight, was discovered eating hay from the adJacent pen at the end of the second weekly period. She was moved to a different stanchion to prevent this, resulting in a marked increase in dry matter intake from silage. Weekly dry matter intakes fir this animal were 68.0, 55.8, 95.2, and 97.0 lb. These problems did not occur in subsequent trials. Table 5 . Average daily dry matter intake per heifer by weekly periods in Trial 1 Group Period 1 2 5 ’4 (1b.) (1b.) (1b.) (1b.) 1" H” Ill-.0 1600 1602 1701 2" Wflted 811888 15 so 13 a 5 13 0‘3 13 06 5- Direct-cut silage 9.6 10.1 11.5 10.6 *9 Average liveweight gains (Table 2) for Groups 1 through 5 were 1. 69, l. 29 and 0. 09 1b. /day, respectively. Gains of Groups 1 and 2 were ‘ .7 significantly. (P 4 0.01) greater than those of Group 5, but the difference between the former groups was not statistically significant. Gains of all groups, however, reflect differences in dry matter intake, and it appears that the consumption of animals fed direct-cut silage (Group 5) was Just sufficient to furnish maintenance energy requirements. Crude protein intake of all groups was greater than the amount listed by Morrison (1950) for animals in this liveweight range. liveweight gains of individual animals are listed in Appendix Table 2. Trial ’2. Animal response to adding acid, Silo-Joy or ground hay to forages Chmnical composition of alfalfa forages utilized in Trial 2 is presented in Table 1i». The addition of hydrochloric acid to the hey did not lower the pH to that of the wilted silage, but approached that of the direct-cut silage. The addition of hay to the direct-cut silage, however, did increase the dry matter content to that of the wilted silage. Dry matter intakes (Table 5) of heifers in Trial 2 indicate that pl! 293 _sg was not responsible for and Silo-Joy did not correct the reduced dry matter intake of silage-fed animals. It should be noted, however, that the mount of acid added per unit of- hay to the ration of Group 1A was not sufficient to reduce the pH to that of the wilted silage, but approached that of the direct-cut silage. Further, only one level of Silo-Joy was used. 8 8 The maximum level reconnended by the manufacturer for addition to forage at time of) ensiling, viz., 1 lb. over tap of load of silage, interpreted to mean 2 tons of fresh forage. Table h. Chemical composition of alfalfa forages utilized in Trial 2 1- . .I'. . .x': . Dry' Crude Ether Crude Nitrogen- Porage * ~" latter protein extract fiber free Ash pH extract 5 ----- (5 of dry'matter)- - - - ---- Hsyécid* Period 1 5.68 Period 2 5.61 Period 5 5.56 Average 5.62 wilted silage fed . . Period 2 22.2 15.8 5.1 58.8 55.h 8.8 h.88 Average 25.h 17.5 5.h 57.8 55.2 8.2 h.92 Wilted silage orts Period 1 51.h Period 2 25.7 Average 28.6 Direct-cut silage fed (lacerated) . Period 1 16.6 15.5 h.2 59.1' 55.5 8.0 5.02 Period 2 19.2 16 6 5.2 57.7 5h.h 8.1 5.11 Period 5 18.5 ---- --- ---- ---- -e- ---- Average 18.1 16.0 5.7 58.h 55.8 8.0 5.06 Direct-cut silage orts Period 1 17.9 Period 2 17.9 Period 5 20.2 Average 18.7 Direct-cut silage + ground hay . Period 2 2h.9 17.0 2.8 55.6 57.0 7.6 Period 5 25.6 ---- --- ---- ---- -e- Average 25.7 17.1 5.2 56.2 56.0 7.5 Direct-cut silage + alfalfe.hay orts Period 1 25.0 Period 2 2h.1 Period 3 23 9;? E * "“Proximate analyses of alfalfa hay listed in Table 1. 7,91 ' Table 5 . Dry matter consumption and average daily gains in Trial 2 * . Group Number Daily 11: intake/ Av. daily Av. daily Av. daily 114 animals 100 1b. liveweight gain dry matter intake /100 lb. during Trial 1 intake liveweight (1b.) (1b.) (1b.) (1b.) .1 h 2A2 1.20 17.0 2.20 1A h 2.55 1.52 16.8 2.12 Av. 1.26 2.51 2 1+ 2.01 1.56 12.2 1.79 2A h 2.01 1.26 15.8 1.79 Av. 1.51 1.79 5 1+ 1.60 0.0!. 9.1+ 1.50 5A h 1.59 0.85 11+.2 1.96 , Av. ‘ Ooh-h 1.73 Std. error 0.212 0.151 ' of a mean 0.150 0.095 "i w . 1 and 1A, hay and hay plus acid; 2 and 2A, wilted silage and wilted silage plus Silo-Joy; 5 and 5A, direct-cut silage and direct-cut silage plus ground hay. 332 Although lowering the pH of hay appeared to have increased, rather than decreased as postulated, dry matter intake per 100 1b. liveweight , the difference between groups was not statistically significant. Average dry matter intakes per 100 1b. liveweight of Groups 2 and 2A were identical at 1.779 1b./1001b. liveweight. Hence the level of Silo-Joy used was ineffective in improving intake. Adding hay, however, to the direct-cut silage increased dry matter intake from 1.50 to 1.96 1b./100 1b. liveweight (siglificant at P {0.05). It should be noted that increasing the dry matter content of the direct-cut silage to that of wilted silage by adding ground hay gave approximately the sane dry matter intake. However, the dry matter of the two rations was not utilized to the same extent as evidenced by the difference in average daily gains . Average daily dry matter intakes per 100 lb . liveweight by forages were 2.51, 1.79, and 1.75 lb. for Groups 1 through 5, respectively. In this trial, as in Trial 1, the hay-fed group consumed significantly (P (0.01) more dry matter per unit weight than the group fed direct-cut silage, and unlike Trial 1, also consumed more dry matter per unit weight than animals fed wilted silage (P < 0.01). The intake difference between Groups 2 and 5 was not statistically significant. This change in intake by animals fed wilted silage can be regarded as another indication of deterioration in quality of the wilted silage during Trials 1 and 2. Inspection of the dry matter intake data by weekly periods (Table 6) reveals no notable changes in dry matter consumption throughout the trial. Although the wilted- silage group declined with time in Trial‘fl, these animals had apparently reached a rather constant low level of intake in Trial 2. Individual dry matter intake data are recorded in Appendix Table 5 . 53 Table 6. Average daily dry matter intake per heifer by weekly periods in Trial 2 .Period (1b.) (1b.) (1b.) 1 - Kw 18.5 16.1 16.5 2 - wilted silage 12.0 12.5 ---- 2A- Wilted silage + Silo-Joy 15$ 111.2 --.-- 5 - Direct-cut silage 9.1 10.5 8.7 5A- Direct-cut silage + ground hay 15.1+ 1h.9 12.0 The addition of acid to hay and. Silo-Joy to wilted silage had no significant effect on average daily gain. The addition of ground hay, however, significantly (P(0.01) increased average daily gain from 0.01; to 0.85 lb. Inspection of average daily gains by forages, reveals that the group fed wilted silage had greater average daily gains than the hay- fed group (1.51 vs. 1.26 lb. 7day) even though thedry matter intake of the former was significantly lower than the hay-fed animals. This difference in average daily gain, however, was not statistically signif- icant. Average daily gain of Group 5 was 0.1.2. 1b. and was significantly (P(0.01) lower than the other two groups. Liveweight gains of individual animals are listed in Appendix Table 5. Trial 5. Animal response to adding water to silage when fed Since water was added to alfalfa silage to give the treatments used in this trial, only dry matter analyses are of interest. The dry matter content of the silage and of the silages as fed are smarised by weekly periods in Table 7. ' at Table 7. Dry matter content of silage fed during Trial 5 by weekly periods * Period 1 2 5 ll» (.5... , 6 7 8 Av. ($) ($) ($) ($0 ($) (i) (i) (i) . (i)~ l 2902 3105 3100 3102 29.0 2900 2805 5107 “#5001 2 2h.5 26.2 25.7 25.9 2h.o 2h.0 25.5 26.1. 25.0 5 19.5 21.14- 20.9 21.1 19.1 19.1 18.5 21.6 20.2 l, alfalfa silage; 2, 5% water added; 5, 10% water added Increasing the moisture content of wilted alfalfa silage at the time of feeding by 5 and 10$ had no significant effect on the dry matter intake per 100 lb. liveweight in Trial 5 (Table 8). Average moisture content of the basal forage averaged.69.9$. This was increased to 75.0 and 79.8% for the experimental treatments. Respective dry matter intakes per 100 1b. liveweight were 2.0h, 2.11;, and 2.09 lb. ~. Average daily dry matter intakes by weekly periods are presented in Table 9. An interesting point is the decreased intake by the control group (Group 1) during the 5-7 week period when the dry matter content of the silage fed decreased. Individual animal intake data are tabulated in Appendix Table 1+. Average daily gain of Groups 1 through 5 were 1.80, 2.52, and 1.87 1b., respectively. we to the extreme variation in weight gains within groups, differences among treatments were not statistically significant. These individual variations in weight gains are shown in Appendix Table h. The general effect of an all-silage ration on animals of different liveweights can be noted from this table. The smaller animals generally exhibited lower average daily gains than the larger heifers. This is in agreement with the results of Thanas, gt _e_l. (1959). Although daily dry matter intakes of the smaller heifersweis lower than that of the larger ones, they were canparable on the basis of dry matter intake per 100 1b. liveweight. . Table 8. Dry matter commption and average daily gains in Trial 5 Group * Number Av. initial Av. daily Av. daily Av. daily animals liveweight gain dry matter In intake/ intake 100 lb . live- weight . (1b.) (1b.) (1b.) (1b.) 1 7 775 1.80 16.2 2.0h 2 7 772 ' 2.52 17.5 2.11. 5, 7 775 1.87 16.6 2.09 Std. error ' of a mean 0.280 0.101, * v 1, alfalfa silage; 2, 5% water added; 5, 10¢ water added Table 9. Average daily dry matter intake per heifer by weekly periods in Trial 5 Grmp PeriOd 1 2 5 1+ 5 6 7 8 (1b.) (1b.) (1b.) (1b.) (1b.) (1b.) (1b.) (1b.) 1 15.2 16.9 17.7 17.8 16.5 15.0 11.9 15.6 2 15.5 17.6 19.2 18.8 18.h ' 17.0 15.9 17.6 5 15.9 171 18.6 17.5 16.1 15.5 15.0 16.8 m in con- trol silage - ' (p) 29.2 51.5 51.0 51.2 29.0 29.0 29.0 - 51.7 *- 1, alfalfa silage; 2, 5% water added; 5, 10% water added Trial 1+. Animal response to adding acetic acid to hay. The dry matter contents: of the alfalfa hay fed and refusals are shown in Table 10. The addition of water or dilute acetic acid to the hay at feeding resulted in a lower dry matter content of the refused hay. Table 10. Dry matter content of hay and orts in Trial ll- Forage Percent dry matter Alfalfa hay fed 82.9 85 .5 Average , 85 . l Alfalfa hay orts ‘ 52 .8 52 . 1+ Average 52.6 Adding acetic acid to alfalfa hay in amounts constituting5$ of the dry matter of the ration had no significant effect on the dry matter intakes (Table 11) . Dry matter intakes for the control and treatment groups were 2.10 and 2.55 lb./100 1b. liveweight, respectively. 5% Table ll. Dry matter intakes and average daily gains in Trial 1+ Group* umber Av. initial Av. daily Av. daily Av. daily animals liveweight gain dry matter m intake/ intake 100 lbs 1‘1”" weight (1b.) (1b.) (1b.) (1b.) 1 8 716 1.98 16.7 2.h0 2 8 716 2.15 16.6 2.55 Std. error ' of a mean 0.182 0.161 *- 1, 1800 ml. water added per 10 lb. hay; 2, 18h ml. acetic acid dilute tolBOOml. addedperlo 1b. hay Average daily dry matter intakes by weekly periods are shown in Table 12. These varied only slightly during the four weekly periods, emphasizing the fact that fluctuations in quality in the hay trial were not of the magnitude of those in the previous trials with silages. Individual. intake data are summarized in Appendix Table 5. Table 12 . Average daily dry matter intake per heifer by weekly periods in Trial 1|- Group * Period 1 2 5 h (1b.) Matt") ri-ailb.) (1b.) 1 16.6 ' 16.7 17.0 16.6 2 16.0 16.l+ 17.1 16.8 l, 1800 ml. water added per 10 1b. hw; 2, 181+ m1. acetic acid diluted to 1800 ml. added per 10, lb. hay Average daily gains in liveweight were 1.98 and 2.15 lb./day for the control and experimental groups, respectively. Although this difference between groups was not statistically significant , as‘Lightly greater gain would. be expected due to the addition of energy in the form of acetic acid if the forage dry matter intake were unaffected by this addition. Live- weight gains of individual animals (Appendix Table 5) are in contrast to V those of the previous trial. The smaller heifers fed hay, unlike those fed silage in Trial 5, made average daily gains canparable to the larger animals. Such was not the case when the animals were fed only silage. DISCUSSION _ Rheults of these trials indicate that dairy heifers voluntarily consume more drymatter fran alfalfa hay'than wilted or direct-cut j .- silage, andmore dry-matter from wilted than direct-cut silage. These observations are in agrounent with numerous reports cited previously using dairy heifers and also with lactating cows (reviewed by Eillman, 1959) . g The first hypothesis tested in these experiments was that pH per _sg was responsible for the depression in dry matter intake since it had been demonstrated that different acids such as lactic (story, 333 3.1., 1961) and acetic (Ueiske and Flechsig, 1889; Liebscher, 1952) depressed forage intake of ruminants. Results of Trial 2, however, indicate that pH £1; E is not responsible for the appetite depression. Evidence supporting this conclusion was also obtained in the comparison of dry matter intakes of heifers fed wilted and direct-cut silage. The latter, although having the highest pH, was eaten in smaller quantities ‘ by the experimental. animals. HiJJJlan (1959) arrived at the same conclusion using a different approach. In this study, the experimental silage was fed with and without added sodium hydroxide to increase the pH to that of hay. The dry matter intake difference between groups was not significant. Although it may be reasoned fran physiological considerations that increasing the hydrogen ion concentration in the reticulo-rumen to a certain high level would result in rumen stasis, anorexia and general acidosis, it appears that the quantity of hydrogen ions in silage is not great enough to reduce drymatter intake. 59 60 The influence of smell. and taste of feeds on nnninsnt dry matter intake has received slight attention. Nevertheless, camnerci‘al flavor cmpounds currently marketed are claimed to improve feed intake of ‘ rmninants (Tribble, 1961) . In Trial 2, Silo-Joy, a commercial flavor preparation, was added to _a given lot of silage at the time of feeding to circumvent possible effects on the fermentation process, and hence, to determine only theeffect of the smell and/or flavor of this canpound . . on dry matter intake. At the level used in this experiment, Silo-Joy had no effect on dry matter intakes of heifers fed wilted alfalfa silage. This is not in' agreement with results reported by Tribble (1961) , who found that adding Silo-Joy to forage at the time of ensiling resulted in increased acceptability of the resulting silage. In view of the results of the present experiment, it is not possible to ascribe any (beneficial effect of Silo-Joy to the smell and taste of silage. The effect ”of this product on the silage fermentation process merits further investigation. Although the possibility exists that smell and flavor differences between alfalfa hay and silage, for example, could be responsible for intake differences, no evidence is available in the literature bearing on these points. Unfortunately, most flavor components tested experimentally have been common cdmnercial flavors which were investigated in preference trials. More information is needed on the specific flavor components in silages and a systmatic" testing of the effect of these compounds on dry matter intake of a given forage, not in preference trials. 61 Considering the additives tested in Trial 2, only ground hay significantly increased dry matter intake. The hay was mixed with direct- cut alfalfa silage at the time of feeding to increase the dry matter con- tent to approximately that of the wilted alfalfa silage used in the same trial, and resulted. in dry matter intakes approaching that obtained fran 'the wilted silage. In effect, this was a supplementary feeding of hay and would be expected to increase dry matter intake of silage fed animals (Hillman, 1959; Waugh, _e_t g” 1955). The increase resulting fran this addition was due to (the hay and apparently caused no change in the acceptability of the silage drytmatter. A more direct approach to the effect of water per 53 on silage dry matter intake was made in the following trial. . The addition of 5 or 10$ water to wilted alfalfa silage at the time of feeding had no effect on the dry matter intakes of dairy heifers . This does not confirm the suggestion of Duckworth and Shirlaw (1958) that wet matter intake controlled appetite. Their conclusion was based on the high correlation between daily dry matter percentage of fresh grass and the dry matter intake on different due. Results of the present trial also fail to confirm experimental results of similar British studies (Dodsworth and Campbell, 1952, 1955; Dodsworth, 1951;) . By increasing silage moisture, content 55 these. workers depressed dry matter intakes of sheep. Rather than attributing this to a species difference, a more likely explanation for these different findings would be the overnight soaking of the silage in the British studies, resulting in a slightly fruity silage odor. water in the present study was added Just prior to feeding. 62 Further evidence that water El: _e_e has little effect on dry matter intake has been presented by Thanas, 9:9 5;. (1961b) who found that drying silage resulted in no increase in consumption and Hillman (1960) who found that soaking hay in water prior to feeding did net reduce dry matter intake. A In addition, there is no definite physiological evidence that water can constitute more than a tmporary "fill" since ruminants have been observed to void tremendous amounts of water via the kidney (Thompson, _e_t _a_l_., 1919). Hence, it appears that water does not act to reduce dry matter intake by merely being present in the silage as fed. Rather, its effect appears to be brought about by altering the silage fermentation process. Reviews of the silage fermentation changes cited previously (watson, 1938; Bender and Bosshardt, 1959; Huffman, 1939; Barnett, 195M Langston, gt _al. , 1958) document experiment-s demonstrating that the moisture content of ensiled forage has a profound effect on the chemical nature of the resulting silage. It is unfortunate, however, that the different experiments are not in agreement concerning the effect of wilting on specific chemical entities. Nevertheless, the data of Nash (1959) indicate that wilting forage results in a reduced percentage of acetic acid in silage in canparisons of direct-cut and. wilted silage. In view of the intake differences in comparison of directs-cut and wilted silage, the hypothesis was made that acetic acid..was a specific inhibitor of dry matter intake and this was tested in the final trial. This metabolite, when added to alfalfa hay to bring the acetic acid content to approximately that of legume silage (Barnett, 195k) , had no effect on dry matter intake of dairy heifers. This finding 63 confirms results of scbmidt and schultz (1958) with lactating cows and Bentley, gt 3.3:. (19510 with growing lmnbs. Results of an interesting experiment have been recently published (Dowden and Jacobson, 1960) following the termination of the present study. These investigators infused into the Jugular veins of dairy cows various short chain fatty acids or their salts and glucose during 8-hr. periods, and measured the effect on dry matter intakes. Glucose, lactic and butyric acids had no effect on feed consumption. High levels of acetic and propionic acids (approximately 12$ of the digestible energy maintenance requirement), however, significantly reduced dry matter intake. A lower level of acetic acid (as of the digestible energy maintenance requirement) had no effect on feed intake. Even though the high levelsof these acids are greatly in :excess of the calculated amounts the average animal would consume; in average silage, these investigators postulate that chamoreceptors affecting feed intake are sensitive to acetic and prOpionic acids. More studies using pm'siological levels of these metabolites are required. Most studies, including the present one, do not offer convincing evidence that acetic acid exerts a specific effect in depressing dry matter intake of silage-fed ruminants. It is well documented, however, that satiety and feeding centers are present in the hypothalamus _of ruminants (Ian-spawn; wyrwicke and Dobrzecka, 1960) . Sensory inputs to these centers, unfortunately, are unknown. The experiment of Dowden and Jacobson (1960) indicates that blood glucose level has no effect on feed intake. From the experiments of Blaster _e_t _a_l_. (1961) , it appears that the authors feel 6% that the physiological mechanisms controlling hunger are. responsiveto - the presence of dry matter in the gastrointestinal tract. _ Their results, using hays of different qualities, indicate that mechanical factors of fill control feed intake. The presence of other mechanismsmay be inferred from North Carolina data (chrthur, 1956) . In this experiment, daily hay intake was reduced from 1.3 lb. /100 lb. liveweight to 0.8 lb. /100 lb. liveweight, and ad libi____t___m concentrate intake during this change remained essentially unchanged, increasing from 35.0 to 55.7 lb. /day. If only fill were operative, an increase in g libitum grain consumption would have been expected when the hay intake was lowered due to decreased fill from the amounts of hay fed. Based on current evidence, the hypothesis of Blaxter, _e_t _a_l_. (1961) also fails to explain the differences between dry. matter intakes of. ruminants fed hay and silage made fran the same cutting. Thanas, gt _a_l_. (1961a)found no difference in retention time of dry matter in the rumen in animals fed hay and silage. Additional studies of this type are needed. Investigation of metabolites other than the volatile acids formed during silage fermentation could possibe reveal chemical entities which depress the Impothalamic areas regulating feed intake. It has been shown (Remark, 1961) that tyramine and serotonin are formed during silage fermentation and small amounts of these compounds exert strong physiological effects in the animal body. MacPherson “‘1ng??? _( l959) found a large increase in gamma- aminobutyric acid when fresh forage was allowed to wilt and was then preserved as silage. The powerful effect of this canpound on central nervous system excitability has been reviewed 65 by Baxter and Roberts (1960) and Albers (1960) . It is possible that such compounds resulting fran silage fermentation could lower dry matter intake. current work, however, including the studies herein, have not yet elucidated the reason(s) . for these hay-silage intake differences. SUMMARY Pour experiments with dairy heifers were carried out in an attempt to elucidate the reasons for observed dry matter intake differences of. heifers fed solely alfalfa m or silage. In the first} trial, intake differences were established by offering animals either all hay, wilted silage averaging 25$ dry matter or high-moisture silage averaging 17 .9$ dry matter in a lI-week trial. All forages were harvested fran alternate areas of the same field of alfalfa in one-fourth bloom. Average daily dry matter intake per 100 lb . liveweight and average daily gain of heifers fed hay and wilted silage were significantly greater than animals fed direct-cut silage. Tested in the second trial were the possibilities that changing the flavor or increasing the dry matter content of silage would improve dry matter consumption, and that lowering the pH of hay to approximately that of silage would reduce dry matter intake. Lowering the pH of hay to approximately that of silage and adding Silo-Joy to wilted silage at feeding time had no significant effect on dry matter intakes or average daily gain in Trial 2. Adding groundhw to direct-cut silage, however, increased dry matter intake to approximately that obtained from wilted silage, but average daily gains were still low. Trial 3 was planned to determine the effect of water addition on dry matter intake when added to a given silage at the time of feeding Increasing the moisture content of wilted silage by 5 or 10$ at feeding time had no siglificant effect on dry matter intake or average daily gain. In a fourth trial, the possibility that acetic acid was a specific 67' depressant of hypothalamic feeding centers was tested by adding acetic ‘ - acid to alfalfa hey at the time of feeding. This addition had no effect on dry matter intake or gains of heifers. Possible reasons for the reduced 'dry matter intake from silage in canparison with hay made from the sane cutting are discussed. Worm Abgsrowicz, F. 19118.01ted by Makela (1956). Adolph, E. r. 19%. Urges to eat and drink in rats. Am. J. Physical 1513110. Albers, R. W. 1960. Gamma-aminobutyric acid. In The Neuro'chemi'stg of Nucleotides and Amino Acids. R. O.‘ Brady and D. B. Tower, ed. John Wiley and Sons, Inc. New York, p. 116. Ananda 13% K. 1961. Nervous regulation of food intake. Physiol. Rev. 77. Anand, B. K. and J. R. Brobeck. 1951a. Mothalamic control cf food intake in rats and cats. Yale J. Biol. Med. 23:125. Anand, 3’ K" and J" R" Brobeek. 1951b- Localization of a "feeding" center" in the hypothalamus of the rat. Proc. Soc. Exp. Biol. Med. 11:523- Andersen, P. 3., J. T. Reid, M. J. Anderson and J. W. Stroud. 1959. Influence of level of intake upon the apparent digestibility of forages and mixed diets by‘ ruminants. J. Animal Sci. _]_.__8:.1299 Anliker, J. and J. Mayer. 1956. An operant conditioning technique for studying feeding fasting patterns in normal and obese mice. Am. J. Appl. Physiol. §_:667. Anon. 1955." Webster's New Collegiate Dictionary. G. and c. Merriam Company. Mammoth; Anon. 1959. Emissary of second silage conference. Beltsville, “83311 9.10. p. 230 Association of Official Agricultural Chuists. 1955. Official and Tentative Methods of _A_n_a%uis of the Association of Official flicultural Chmists. th‘ed. Washington» Bailey, G. I», c. c. Balch and J. C. nird'ech. 1955. The digestibility and feeding value of a lucerne/timothy award ensiled in four ways. J. Brit. Grassland soc. _lg: 27. Banter, K. and I. Vitai. 1956. Szecskazas hatasa a szarvasmarhak zoldtakarmsny fogyasztasara. (Influence of chopping on the green feed consumption of cattle). Rept. rec. Animal mm, Bung. Univ. Agric. sci. No. 5, p. 257. (Nutrition Abs. Rev. 28: 635. 1958) 69 Belch, C.‘ C. 1950. hetors'affecting the utilization of food by dairy cows. I. The rate of passage of food through the digestive tract. Brit. J. Nutrition h: .561. Belch, C. C. 1958. Observations on the act of eating in cattle. Brit. J. Nutrition12 5.50. Balch, C. C., J. C. Murdoch and J. Turner. 1955. 'The effect of chopping and lacerating before ensiling on the digestibility of silage by cows and steers. J. Brit. Grassland Soc._]_._g:526.. Baltzer, A. C., B. J. Killha'n, C. v. Duncan and C. F. Bufman. 19h1. A cobalt deficiency disease“ observed in' some Michigan dairy cattle. MichiganAgr. Expt. Sta. Quart._Bu11. 25:68.. Barnett, A. J. G. 1951}. Silage Fermentation. Academic Press, Inc. New York. Barter, C. F. and D. Roberts. 1960. Gma—aninobutyric acid and cerebral metabolism. In The Neurochemistry of Nucleotides and Amino Acids. R. 0. Brady, and *D. B. Tower, ed. John Wiley and Sons, Inc. New York. p. 127. Beidler, L. M. 1957'. Facts and theory on the mechanism of taste ‘and odor perception. Chemistry of Natural Food Flavors. A‘ symposium sponsored by National Acadaw of Sciencesa-National Res. Council for Quartermaster Food and Container Inst. for the Armed Forces and Pioneering Res. Div., Q.M. Res. and Engineering Center. P- 7. Bender, c. s. l9h2. Feeding grass silage. New Jersey Agr. Expt. Sta. Bull. 695. Bender, C. B. and D. K. Bosshardt. 1959. Grass silage: A critical review of the literature. J. Dairy Sci. 22:657. Bender, C. B. and H. H. Tucker. 1957. Timothy silage as a dairy feed. New Jersey Agr. Expt. Sta. Ciro. 57h. Bendar, Co 30,30 He TUCker, V. Ce meger, Xe 0. Pt“ and Ac Se Fox. 1956. Molasses hay silage. J. Dairy Sci. _2: 157. Bentley, 0. G., T. V. Hershberger, L. B. Kunkle and D. S. Bell. 1951+. The nutritive value of acetate, propionate and lactate for lambs. (Abs.) J. Animal Sci. -:_L2: 976. 70 Bentley, 0. G., R. R. Johnson, G'. 3. Royal, F. Deatherage, L. E. Kunkle, W. J. Tyznik and D. S. Bell. 1956. Studies on the feeding value of acetic, propionic and lactic acids with paving-fattening la'abs. 01.10 m... We 815... Re.- Balls 77km Bernstein, L. M. and M. I. Grossman. 1956. An experimental test 'of"the glucostatic theory of regulation of food intake. J. Clin. Invest. 55:627. Blaxter, K. L. 1950. Energy feeding standards for dairy cattle. Nutrition Abstr. Rev. _29_: l. Blaxter, K. L. and N. McC. Grahm. 1956. The effect of the grinding ' and cubing process on the utilization of the energy of dried grass. Jo Agra 8010 sz're Blaxter, K.. In, N. Mcc. Graham and F. v. Vainman. 1956. Same observa- tions on the digestibility of food by sheep and on related problem. Brit. J. Nutr. _l_0__:69. mater, Ks In, F. "a VW ma. Re So “flame 19610 The regul‘tion of food intake by sheep. Animal Prod. 5. 51. Brobeck, J. R. 19h8. Food intake as a mechanism of temperature regulation. Yale J. Biol. Med. 20: 5&5. Burroughs, 11., P. Gerlaugh, E. A. Silver and A. E. Scha'Lk. 191+6. The amount of feeds and nutrients in the lumen of cattle throughout a all—hour period as affected by plane of feeding and character of ration. J. Animal Sci. 5. 558. Camburn, 0. M., H. B. Ellenberger, J. A. Nevlander and C. H. Jones. 1957. Dry vs. succulent roughage in the dairy ration. Vermont Agni. Expt. Sta. Bull. h12. Cannon, V. B. and A. L. Washburn. 1912. An explanation of hunger. Am. J. Physiol. amid. Carlson, A. J. 1916. The Control of Hunger in Health and Disease. The Univ. of Chicago Press. Chicago. Cass, L. J. 1959. Evaluation of appetite suppressants. Ann. Int. Med. 51:1295. Castle, B. J .7 1956. The rate of passage of foodstuffs through the alimentary tract of the goat. I. Studies on adult animals fed on hay and concentrates. Brit. J. Nutr. 19:15. 11 Chance, 0‘. M. , C. F. Huffman and C. V.‘ Duncan. .1955. Antibiotics in rumen digestion and synthesis. 1. The effect of aureainCin on ' r'umen digestion and the passage of nutrients fru the men during specific intervals after feeding. J. Dairy Sci. 56 255. Cipollcani, M. A. , B. H. Schneider, H. L. Lucas, and H. M. Pavlech. 1951. . Significance of the differences in digestibility of feeds by cattle and Sheep. Jo m 8310 1.9.3337. Colovos, N. F., n. A. Keener and H. A. Davis. 1957. Errors in‘dr'ying silage and feces for protein and energy determinations. Inproved procedures. J. Dairy Sci. _hg: 175. . Converse, H. r. 1955. Cited by Sykes, at al. (1955). Crmpton, E. U. 1957. Interrelations between digestible nutrient and energy content, voluntary dry matter intake and the overall. feeding value of forages. J. Animal Sci. 16:516. Cram, 3. 1955. Cited by Makela (1956) . De Man, J. C. 1952'. Influence of curshing on the pH of grass silage. Nature 1.65:286. Dodswort’h, T. L. 1951'». Further studies on the fattening value of grass silage and on the effect of the dry-matter percentage of the diet on dry-matter intake in rtnninants. J. Agr. Sci. 55:585. Dodsworth, T. L. and V. H. M. Cmpbell. 1952. Effect of the percentage of dry matter in the diet on the dry-matter intake in ruminants. Nature 34?: 1128. Dodsvorth, T. L. and v. H. M. Campbell. 1955. Report on a further experiment to compare the fattening values for beef cattle, of silage made from grass cut at different stages of growth, together with the results of some supplementary experiments . Jo Agr- 8010 £31.66. Daugherty, R. v., C. S. Klavano, v. M. Dickson and P. A. Klavano. . 1956. Blood sugar levels in cattle and sheep fed various amounts of glucose. Cornell Vet. £397. Dovden, D. R. and D. R. Jacobson. 1960. Inhibition of appetite in dairy cattle by certain intemediate metabolites. Nature _2_L_§_8:1h8. Duckworth, J. B. , and D. V. Shirlaw. 1958. A study of factors affecting feed intake and the eating behavior of cattle. Animal ihhavior _6zlh7. T? Ely, R. 3.; K.'M. Dunn and C. F. Huffman. 19h8. Cobalt toxicity in calves resulting from high oral administration. J. Animal Sci. 1: 259. new, Re So, Lo Do W, Go Fa Hum, To BC MB, Jo Po Mrs‘bt and C. A. Lassiter. 1961. Calparative feeding value of lactic acid and groin for dairy cattle. J. Animal Sci. _2_0_:l59. Basig, H. w., 3.1:. Hatfield and B.' C. Johnson. 1959. Volatile fatty acid rations for growing lambs. J. Nutrition 62:155. Everett, Jr. J.'P., L. D. Brown, C. A. Lassiter, D. R. Jacobson and J. V. Rust. 1958 Auremycin as a protein-sparing agent and its influence on minimum starter protein level satisfactory for normal growth of dairy calves. J. Dairy Sci. L1: 1107. suing, P. v. and L. H. wright. 1918. A'study. of the. pluraical changes inthed’mesidnes which take place in cattle during digestion. J. Agr. Res. 55:659. Findlay, J.‘ n. 1958. Physiological reactions of cattle to climatic stress. Proc. nutrition Soc. 31:186. Fissmer, F. E. 1991. Beitrage zur frage der sattigung bei der milchkuh. (The question of satiety in milk cows.)' Tierer. Futter mittilk. 5. 1 (Nutrition Abstr. Rev. _1: 269 191.7) Foreman, C. F., R. 8. Allen, A. R. Porter and P. G. Haneyer. 1958. Comparison of alfalfa fed as soilage or silage as the only forage for lactating dairy cows. J.‘ Dairy Sci. 31:1750. Fousberg, A. and S. Larsson. 1951;. On the hypothalamic organi- .sat'ion of the nervous mechanism regulating food intake. Part II. Studies of isotope distribution and chemical composition in the hypothalamic region of hungry and fed rats. A313. maiolo scmdm 323mo 1.15. pa llJ-o i Frandsen, J. H. 1958. Dairy Handbook and Motiogg. Nittanv Printing and Publishing quany, State College, Pennsylvania. Do 3870 . Fred, B. B. and U. H. Peterson. 192%. aniling partially dried alfalfa. Wisconsin.Agr. mt. 81:... Bull. 362. ' Fryer, Jo Fe, No Be more, Ho-Ho ”1111”. Ind. Co M. Younso l955‘o A study of the interrelationship of the energy-yielding nutrients, blood glucose levels and subjective appetite in man. J. Lab. Clino “ed-o 3423681}. 73 Fryer,‘J. H., N.’S. Moore, H. H. William and C. M. Young. 1955b. Satiety values of isocaloric diets for reducing with special reference to the glucastatic theory of appetite control. J. Am. Dietetic Assoc. 5_: 1868 Goetsch, G. D. and v. R. Pritchard. 1958. Effects of oral administra- ' tion of short-chain fatty acids on certain blood and urine ' constituents of fasted, phlorhizin-treated ewes. Am.J. Vet. Res. 12:657. Goldstein, s. 1950 Cited by Makela (1956). Gordon, C. H., C. G. Melin, H. G. Viseman, H. M. Irvin and J. R. McCaJmont. 1958. Chemical quality, nutrient preservation and feeding value of silage stored in bunker silos. J. Dairy Sci. 31:1758. Gordon, 0. H., E. A. Kane, J. C. Derbyshire, V. C. Jacobson and C. G. Melin. 1959a. Nutrient losses, quality and feeding values of wilted and direct-cut orchard grass stored in bunker and tower silos. J. Dairy Sci. 1+2: 1705. Gordon, 0. H. , H. G. Hiseman, J. c. Derbyshire and V. C. Jacobson. 1959'!» Effect on silage of chipping and bruising the forage. J. Dairy Sci. 1:2: 159+. Gordon, J. G. 1957.Pa1atability in relation to physiological needs. Advance. Sci. _5: 296. Gordon, J. G. 1958a. The effect of time of feeding upon nomination. Jo Ago SCio 21.381. Gordon, J. G. ° 1958b. The relationship between fineness of grinding food and rumination. J. Agr. Sci. 51:78. Grossman, M. I. 1958. Regulation of food intake. Am. J. Dig. Dis. 5:659. Grosaman, M. I. and I. F. Stein, Jr. 19h8. Vagotomy and the hunger- producing action of insulin in man. J. App. Pm'siol. 1:265. Hancock, J. 1955. Grazing behaviour in cattle. Animal Breeding A1330 21:1o Harshbarger, K. E. 1919. Observations on the time required for dairy cows to eat grain, silage and hay. (Abs.) J. Dairy Sci. 53:716. Henderson, Jr. , B. H., and C. 1.. Norton. 1950. Grass silage for dairy cattle. Rhode Island Agr. Bxpt. Sta. Bull. 511. 7t Hervey, G. R. 1959‘. The effects of lesions in the hypothalsnnls in parabiotic rats. J. Physiol. _5: 556. Hesselbarth, K. 1951:. Untersuchugen uber fresslust, futt‘eral‘lfnahi- ' ” mevelmogen und futterverwertung bei milchkuhem. (Appetite capacity and utilization of feed by dairy cows.) Arch. Tierer 3: °1&5. (Nutrition Abstr. Rev. 25: 555. 1955). Hetherington, A. w. and S. V. Ransom. 1959. Experimental hypothalamico- hypophyseal obesity in the rat. Proc. Soc. Expt. Biol. 51:1:65. Hetherington, A. w. and s'. w. Ransom; 191:0. 'Hypothalamic lesions and adiposity in the rat. Anat. Rec. 18:119. Hetherington, A. H. and S. U. Ransom. 191:2. Thespontaneo'us activity ' and food intake of rats with hypothalamic lesions. Am. J. Physiol. 122:609 Hill, D. L., C. H. Noller, B. V. Growl and N. S. Lundquist. 1957. _A plastic silo. Purdue Univ. Expt. Sta. Mimeo DH-65. Pullman, D. 1959. Appetite studies in daiq cattl . Grass silgg vs. m. Ph.D. Thesis, Michigan State Univ. East Lansing. Hoelzel, F. 1957. Dr. A. J. Carlson and the concept of hunger. Am. J. min. Nutrition 5. 659. Hollifield, G.,U.Parson and K. R. Crispell. 1955. Studies of food drive and satiety in mice with gold thioglucose-inducedobesity and the hereditary obesity-diabetes syndrane. Metabblism fig: 557 . Hoover, V. H., N. H. Gotwalt and E. M. Kesler. 1959. Influence of roughage quality on growth of young holstoin calves. Pennsylvania Progress Rept. 202. Houssoy, B. A. 1955. Human msiolog. 2nd ed. McGraw-Hill Book Canpany, Inc. New York. 'p. 552. Huffman, C. F., C. N. Duncan, G. 8. Robinson and L. w. lamb. 1955. Phosphorus requirments of dairy cattle when alfalfa furnishes the principal source of protein. Michigan Agr. Expt. Sta. Tech. Bull. 15h. Huffman, C. F. 1959. Roughage quality and quantity in the dairy rations: A review. J. Dairy Sci. _2_2__:_889. airman, c. r. 1959a. Nutritional evaluation of silage. Proc. Michigan State University Silage Conf. , East Lansing. p. 85. 75 Huffman, C. F. 1959b. Summer feeding of dairy cattle: A review. J. Dairy Sci. 3:11-95. mm, c. F., s. r. Dexter, c. w. Duncan and c. A. Lassiter. 1957. Grain— equivalent of imature alfalfa for milk production when fed as soilage and. as silage. J. Dairy Sci. £03261}. Hutcheson, T. B. , T. K. Wolfe and M. S. Kipps. l9h8. The Production of Field Crops. 5rd ed. McGraw Hill Book 00., Inc. New York. p. 155. Jasper, D. E. 1955a. Acute and. prolonged insulin hypoglycemia in cows. Am. J. Vet. Res. _J_._1_t:l8h. Jasper, D. E. 1955b. Prolonged insulin hypoglycemia in sheep. 53.5. Vet. Reao E3209. Jones, M. 1952. Characteristics of grasses and legumes in relation to their requirements for silage making. Proc. 6th Intern. Grassland Cong. @1127. Kare, M. R. 1959. Some practical aspects of the sense of taste in danestic animals. Proc. Cornell Nutrition Conf. p. 101. Keener, Ho Ao, Fo E. Allen, No Fo COlovoa, Ao C. M and. H. As Evie. Value of adding corn silage and limited quantities of hear to a grass silage, limited grain ration for dairy heifers. J. Dairy Sci. 1&1: 1429. Keener, Ho Ao, No Fe COlovoa, Ko 8o M030“) Go Mo W, . . r G. P. Percival and J. R. Prescott. 1919. The relative feeding value of a forage preserved by ensiling, mow curing and field curing. New Hampshire Expt. Sta. Ciro. 77. Kefford, N. P. 1958. Lignification of plants in relation to ruminant nutrition. J. Australian Inst. Agr. Sci. @5297. Kennedy, 0. C. 1955 . The role of depot fat in the hypothalamic control of food intake in the rat. Proc. Roy. Soc. (London) B. Kennedy, G. C. 1956. The developnent with age of mothalamic , restraint upon the appetite of the rat. J. Mocrmlogy-lé:9. Keyes, E. A. and E. P. Snith. 1955. The feeding value of alfalfa for dairy cows when harvested and stored by four different methods. Montana Agr. Expt. Sta. Bull. 515. 76 Kochakian, C. D. and J. Webster. 1958. Effect of testosterone pro- pionate on the appetite, body weight and. composition of the normal rat. hidocrinology 65:757. Kruger, L. and W. Muller. 1955. Uber mtteraufnahne und verzehrleistungen bei milchkuhen. 1. Kine theoretische betrachtung sun problaa der sattigung. (Peed intake and consumption in milk cows. 1. Theoretical consideration of the problan of satiety). Zuchtungskunde £317.. (Nutrition Abstr. Rev. 56:229. 1956). Kruger, L. and. G. Schulze. 1956. Uber futlerauhnahme und verzehrleistungen bei milchkuhen. 5. Die sattigungsbewertung der futtemittel. (Feed intake. and consumption in milk cows. 5 . The satiety value of feedingstuffs.) Zuchtungskunde _2_§:h58. (Nutrition Abstr. Rev. g1:569.,1957) Kruger, L. and G. Schulze. 1958. Die futteraufnahne fahigkeit von kuhen und der sattigungswert von futtemitteln. (The feed capacity of cows and the satiety value of feedingstuffs.) Tierzucht. Zuchtungsbiol. 12:55. (Nutrition Abstr. Rev. 29:680. 1959.) Kuhn, J. 1875. Cited by Makela (1956). Lsmbourne, L. J. 1957. Measurement of feed intake of grazing sheep. 1. Rate of passage of inert reference materials through the ruminant digestive tract. J. Agr. Sci. fizzy}. Langston, C. H., H. Irvin, G. H. Gordon, C. Home, H. G. Uisman, ' C. G. Melin, L. A. Moore and J. R. McCalmont. 1958. Microbiology and. cmatry 0: @833 8118ng UoBoDvo TCCho Bull. 1187o Larsson, S. 1951;. On the hypothalamic organisation of the nervous mechanism regulating food intake. Part 1. mperphagia from stimulation of the hypothalamus and medulla in sheep and goats. Acta Physiol. Scand. 52: Supp. 1.15. p. 1. ' Laesiter, C. A. 1955. Antibiotics as growth stimulants for dairy cattle: A review. J. Dairy Sci. 1533:1102. Lassiter, C. A., C. F. W, S. T. Dexter and C. W. Duncan.l958. Corn versus oat silages as a roughage for dairy cattle. J. Dairy Sci. 5131282. Lehmann, 1". 191a. Cited by Makela (1956). 77 Lepkovsky, S. 191:8. The physiological basis of voluntary food intake (appetite). Adv. Food Res. _1_:105. Lepkovsky, S. 1955. The action of various deleterious cwounds on voluntary food intake. Ann. NJ. Acad. Sci. 62:152. Iepkovsky, 8., R. Lyman, D. Planing, M. Nagumo and M. M. Dimick. 1957. Gastrointestinal regulation of water and its effect on food intake and rate of digestion. Am. J. Physiol. 1883527. Liebsoher, w. 1952. Cited by Schoch (1957). MacKay, E. M. , J. N. Galloway and R. H. Barnes. 1910. Meralimentation in normal animals produced by protamine insulin. J. Nutrition _2_0_:59. MacPherson, H. T. and J. S. Slater. 1959. Gama-amino-n-butyric, aspartic, glutamic and pyrrolidonecarboxylic acid: their determination and occurrence in grass during conservation. Biochem. J. 11:65h. Mahala, A. 1956. Studies on the question of bulk in the nutrition of farm animals with special reference to cattle. Acta. Agral., Fennica 85:1. Manning, H., G. I. Alexander, H. M. Krueger and R. Bogart. 1959. The effect of intraveneous glucose injections on appetite in adult ewes. Am.J.Vet. Res. _29_:2h2. Martin, U. G., H. A. Ramsey, G. Matrone, and G. H. Wise. 1959. Responses of young calves to a diet containing salts of volatile fatty acids. J. Dairy Sci. ’4__~2_:1577. Martz, r. A. , C. H. Noller, D. L. Hill and M. U. Carter. 1959. Intake and value for milk production of oat silages ensiled 'at three stages of maturity and preserved with sodium metabisulfite. J. Dairy Sci. 32:1955. Mather, R. E. 1959. Can dairy cattle be bred for increased forage fignmmtion and efficiency of utilization? J. Dairy Sci. :878. Matrone, G., H. A. Ramsey and G. H. Wise. 1959. Effect of volatile fatty acids, sodium and potassium bicarbonate in purified diets for ruminants. Proc. Soc. mt. Biol. Med. 129:8. 78 Meyer, J. 1955.. The physiologic basis of obesity and leanness. Nutrition Abstr. Rev. 25:597 and 871. War, J. 1957a. Hunger and. thechypothalamus. Clinical Res. Proc. A 5:125. Mayer, J. 1957b. Some advances in the study of the physiologic basis of obesity. Metabolism 6:155. ' Meyer, J. 1958. Physiological and. nutritional. aspects of obesity. Borden's Rev. Nutrition Res. 12:55. Meyer, J. and S. D. Morrison. 1958. Functional recovery after lesions in the lateral hypothalamus of rats. J. Physiol. 135ml. Meyer, J., J. J. Vitale and M. V. Bates. 1951.. Mechanism of the regulation of food intake. Nature .l_61:562. Maynard, L. A. and J. K. Loosli. 1956. Animal Nutrition. 5rd ed. McGraw Hill Book Coi.., Inc. New York. p. . 14mm, w. C. I 1956. An economic analysis of feed utilization for milk production in North Carolina. Unpublished Ph.D. thesis, North Carolina State College. p. 89. McCullough, M. E. 1956. A study of techniques for measuring differences in forage qgality using dairy cows. Georgia Agr. Expt. Sta. m1. NoSo I I McCullough, u. s. 1959. Conditions influencing forage acceptability and rate of intake. J. Dairy Sci. £571. McCullough, M. E. and H. E. Neville, Jr. 1959. Some factors affecting weight gains of dairy heifers fed all-roughage rations. J. Dairy Sci. £23698. Mead, S. V. and H. Goes. 1956. Sane results of eight years of investi- gations concerning the role of roughage in the diet of ruminants. (Abs.) J. Dairy Sci. _l_.9:’+65. Mellinkoff, S. M. , M. Frankland, D. Boyle and M. Greipel. 1956. Relationship between sertm amino acid concentration and fluctuations in appetite. J. App1._Ehyaiol. _8_:555. Meyer, J. H. ,'R. L. Gaskill, G. S. S'toewsand and N. C. Heir. 1959a. . Influence of pelleting on the utilization of alfalfa. J. Animal Sci. 18:556. 79 Meyer, J. H., v. C. Weir, J. B. Dobie and J. L. Hull. 1959):. Influence of the method of preparation on the feeding value of alfalfa hay. J. Animal Sci. 18: 976. Mikhin, A. 14., v. u. rokin and A. A. Tupikova. 1936. Cited by Bender and Bosshardt.(l959) . Miller, N. E. , C. J. Bailey and J. A. F. Stevenson. 1950. Decreased "hunger" but increased food intake resulting from hypothalamic lesions. Science _1_1_2:256. Miner, R. w. 1955. The Regulation of W . Ann. N.Y.. Acad. Sci. 65:1. Monroe, C. F., J. H. Hilton, R. E. Hodgson, U. A. King and N. E. Krauss. 19%. The loss of nutrients in hay and meadow crop silage during storage. J. Dairy Sci. 22:259. Moore, L. a. 1958. Problems and recent improvements in the preparation and. use of grass silage. U.S.D.A. Publ. A.R.S. hit-25. Moore, 1.. A., J. w. Themes, w. c.“ Jacobson, C. o. Melin and. J. 13. Shepard; l9h8. Ccmparative antirachitic value of field-cured hay, barn-dried hay “grad wilted grass silage for growing dairy calves. J. Dairy Sci. 51:; . Morrison, 1". B. 1950. Feeds and Feeding. 21st ed. Morrison Publ. Co. Ithaca, N. Y. Morrison, S. D. 1959. Obesity and the control of food intake in ~: experimental animals. Proc. Nutrition Soc. l§zlhl. Morrison, 8. B., R. J. Barrnett, and J. Meyer. 1958. Localization of lesions in the lateral hypothalamus of rats with induced adipsia and aphagia. In. J. Physiol. 1922250. Murdoch, J. G., C. C. Balch, M. C. Holdsworth and M. Wood. 1955. The effect of chopping, lacerating and wilting of herbage on the cheaical cmposition of silage. J. Brit. .Grassland Soc. 12:181. Murray, J. A. 1926. The food. capacity of cattle. J. Agr. Sci. _l_6_:57h. Nash, M. J. 1959. Partial wilting of grass crops for silage- 2. Experi- mentalsilages. J. Brit. Grassland Soc. _l_._l_L:107. . remark, H. 1961. Amines in silage. Nature 123859. 80 Newlander, J. A. and W. H. Riddell. 1957. High-moisture versus wilted gass silage for raising dairy calves. Vermont Ag. Expt. Sta. Bull. 602. Nicholson, J. N. G. and R. C. Parent. 1957. Various canbinations of grass silage and hay for dairy cattle. Can. J. Animal Sci. 51:61:. Paloheimo, L. and A. Makela. 1959. Further studies on the retention time of food in the digestive tractof cows. Acta. Agral. . Fennica 932:1. Passmore, R. 1958. A note on the relation of appetite to exercise. Lancet, January 1+. p. 29. Passmore, R. and F. J. Ritchie. 1957. The specific dynmnic action of food and the satiety mechanism. Brit. J. Nutrition 11:79. Pekas, J. C., G. E. Canbs, J. M. Vandepopuliere and H. D. Wallace. 1959. Ibrpoglycemic camounds as appetite .stimulants for baby pigs. J. Animal Sci. 18:1282. Palmer, L. 19:5. The treatment 0f obesity by appetite control: The '- use of autonomic substances and their synergists. Ann. Internal. Med. 22:201. Pfafmann, c. 1952. Cited by Beidler (1957). Phillipson, A. T. 191:8. A method of measuring the flow of digests fruit the stomach of the sheep. J. Physiol. 191:21. Piana, C. 1952. Tempo di passaggio degli alimenti nele-apparato - dizerente di ovini privati del rumine. - (Time of passage of food through the digestive tract of sheep from which the rumen hedg- been removed.) Zootec. Vet. 3M5. Piatkowski, B. 1958. Vergleichenda verdsulichkeitsstudien an ausgewachsenen wiederkauern der verschiedenen arten. (Cunparative studies of digestibility in adult ruminants of different species.) Arch. Tiarernahrung Tierzucht 8:595. (Nutrition Abstr. Rev. §:669. 1959-) Piskunov, N. I. 1958. Vlijnie. silosa na organism molodnJaka krupnogo rogatogo skota. (Influence of silage on young cattle.) Zivotnovodstvo 5:51. (Nutrition Abstr. Rev. 32:516. 1959) ‘ PoiJarvi, I. 1919. Cited by Makela (1956). 81 Porter, G. H., R. E. Johnson, H. D. Eaton, F. I. Elliott and L.A. Moore. 1955 . Relative value for milk production of field-cured and field- beled, artificially dried-chopped, artificially dried-gound and artificially dried-pelleted alfalfa when fed as the sole source of ;.ronghage to dairy cattle. J. Dairy Sci. 56:11“). Porter, G. H. and E. M. Healer. 1951+. The value of gass silage in . the diet of the young dairy calf. J. Animal Sci. 15:1010. Pott, a. 1901:. Cited by Makela (1956). Pratt, A. D. , R. G. Washburn and C. P. Rogers. 1958. Canparative palatabilities of silages. Ohio Ag. Expt. Sta. Res. Bull. 81%. Ragsdala, A. C., H. J. mm, D. M. Worstell and S. Brody. 1950. mvironmental physiology with special reference to domestic animals. 9. Milk production and feed and water consumption responses of Brahman, Jersey and Hglstein cows to changes in tmperature, 50° to 105° F. and 50 toC.8° F. Missouri Ag. Expt. Sta. .Be’s’. Bull. 14-60. Ratcliff, L. 1959. Why feed calves good hay? Hoardv'vs Dairyman lou(1):22. Raymond, W. F., C. E.‘ Harris and C. D. Kemp. 1955. Studies in the digestibility of herbage. VI. The effect of level of herbage intake on the digestibility of herbage by sheep. J. Brit. GrasslandSoc. _l_.9_:19. Reed, 0. s. and. J. R. Fitch. 1917. Alfalfa silage- Kansas Agr. axpt. Sta. Bull. 217. Reid, J. T., W. K. Kennedy, K. L. Turk, S. T. Slack, G. W. Trimberger andsR. P. Murphy. 1959. ‘ffimposium on forage evaluation: I. What is forage quality fran the animal standpoint? ‘Agron. J. 2:215. Rim, A. A. 1958. Factors affecting roughage consumptime the dairy cow. M. S. Thesis. Rutger's Univ. , New Brunswick. Rogers, C. F. and D. S. Bell. 1955. Acceptahility of high-drymatter silages. Ohio Ag. Expt. Sta. Res. Ciro. 20. Ronning, H., J. E. Meyer, and G. '1‘. Clark. 1959. Pelleted alfalfa hay for milk production. J. Dairy Sci. 3331575. Savage, E. S. and C. B. Bender. 1959. Grass Silage. Cornell Ext. 30.11.1409. w _ , I " - ' . . 82 Schmidt, G. H. and L. H. Schultz. 1958. Effect of feeding sodium pro- pionate on milk and. fat production, roughage consumption, blood sugar and. blood ketones of dairy cows. J. Dairy Sci. 31:169. Schoch, W. 1957 . The influence of silage on the metabolism of animals and the quality of animal products. Making and Nee of 811 e. Organization for European Econanic Cooperation (formerly CEEC Publ. Project 507. Paris. '1). 121. Schubert, A. H., B. R. Churchill and J. G. Wells, Jr. 1910. Effects of feeding various lots of legume gass silage to dairy cattle. Michigan Ag. Expt. Sta. Quart. Bull..g_2_:258. Sears, P. D., r. s. Sill and R. P. Newbold. 19:2. The apparent digestibility of smples of pasture silage. New Zealand J. Sci. Tech. (A) _a_hz9l. Share, 1., E. Martyniuk and M. I. Grossman. 1952. Effect of prolonged intragastric feeding on oral food intake in dogs. An. J. Physiol. _§2:229 Shepherd, J. B., C. H. Gordon, H. G. Wiseman, C. G. Malia, L. E. Campbell and G. D. Roane. 1955. Cmari-sons of silages stored in gas—tight silos and in conventional silos. J. Dairy Sci. 5_6_: 1190. Sherringtbn,.C. s. 1900. Cited by Brobeck (1957). Snedecor, G. 'W. 1956. Statistical Methods. 5th'ed. Iowa State College Press. Amos. ' Stallcup, O. T., D. V. Bostain, and. K. P. Bierworth. 1959. Time required for dairy cows to eat concentrates and silage. Arkansas Agr. m. 8ta.Bull. 609. Stallcup, ,0. T., J. L. Cason, and B. J. Walker. 1956. Influence of ' the lignin content of hby-on the passage of nutrients through the rumen. Arkansas Ag. Expt. Sta. Bull. 572. Stone, J. B., G. W. Trimberger, C. R. Henderson, J. T. Reid, K. L. Turk and us. Loosli. 1959. We intake and efficiency of feed utilization in dairy cattle. Proc. Cornell Nutrition Conf. p. 51. Strang, J. M. and H. B.McClugage. 1951. Cited by Brobeck (1957). 33 Straninger, J. L. and J. R. Brobeck. 1953. A mechanism of regulation of food intake. Yale J. Biol. Med. Q58}. Strcminger, J. L. , J. R. Brobeck and R. L. Cort. 1953., Regulation of food intake in normal rats and in rats with hypothalamic hyper- phagia. Yale J. Biol. Med. g_6_:55. Stunkard, A. J. and H. G. wolff. 1956. Studies on the physiology of hunger. I. The effect of intravenous administration of glucose on gastric hunger contractions in man. J. Clin. Nutrition 22:95!» Stunkard, A. J. and H. G. wolff. 1958. Pathogenesis in human obesity. Function and disorder of a mechanism of satiety . Psychosomat. Med. _2_9 :17. Stunkard, A.‘J., T. B. VanItallie and B. B. Beis. 1955. The mechanism of satiety: effect of glucagon on gastric hunger, contractions in man. Proc. Soc. Exp. Biol. Med. §2=258. sypboda. r. 1937. Cited by Mahala (i956) . Sykes, J. F., H. T. Converse and L. A. Moore. 1955. Canparison of alfalfa hay and alfalfa silage as roughage for growing dairy heifers in a limited milk and grain feeding system. J. Dairy Sci. 58:12h6. Thanas, J. H., J. R. Ingalls, M. Yang and B. S. Reddy. 1961a. Effect of g libitum or equalized feeding of alfalfa hay or silage on rumen content and its characteristics. Paper 121. Am. Dairy Sci. Assoc. Univ. Wisc., Madison. Thmas, J. H., L. A. Moore, M. Ckamoto, and J. P. Sykes. 1961b. A study of factors affecting rate of intake of heifers fed silage. J. Dairy Sci. 3311471. Thomas, J. H., J. F. Sykes and L. A. Moore. 1957. A canparison of alfalfa hay and wilted alfalfa silage as roughage for growing dairy calves. (Abs.) J. Dairy Sci. 3193626. Thomas, J. H., J. 1". Sykes, and L. A. Moore. 1959. Cmparison of alfalfa hay and alfalfa silage alone and with supplements of grain, hay or corn silage for growing dairy calves. J. Dairy Sci. 32:651. 81+ Thanpson, H. J. , D. M. Worstell and S. Brody. 1911-9. Environmental physiology with special reference to danestic animals. V. Influence of temperature, 50° to 105° F., on water consumption in dairy cattle. :Missouri Ag. Expt. Sta. Res. Bull. 166. Tribble, 1'. a. 1961. Taste Stage Feeding.(Brochure) . Flavor Corp. of America. Tribe, D. E. 191L9. The importance of the sense of smell to the gazing sheep. J. Ag. Sci. 22:509. Tuckerman, B. 1891. Cited by Beidler (1957) . VanItallie, T. B. , R. Beaudoin,=and J. Mar. 1955. Arteriovenous glucose differences, metabolic hypoglycemia and food intake in man. J. Clin. Nutrition _l_:208. Watson, C. J., W. M. Davidson, J. W. Kennedy, C. H. Robinson, and G. W. Muir. 19’48. Digestibility studies with ruminants. 12. The comparative digestive powers of sheep and steers. Sci. Ag. £83357. ‘ ' Watson, 3. J. 1958. Silage and _Crpp Preservation. MacMillan and Co. London. Watson, S. J. 1957 . Nature and preparation of the geen crop and silage preservation. Makiggand Feedingfiof Silage. Organization for European Economic Cooperation (formerly no) Publ. Project 307. Paris. p. 59. Waugh, R. H., H. S. Poston, R. D. Mochrie, W. R. Murley, and H. L. Lucas. 1955. Additions of hay to corn silage to maximize feed intake and milk production. J. Dairy Sci. 283.688 Weiske, H. and E. Flechsig. 1889. Cited by Schoch (1957). Woodward, T. B. and J. B. Shepherd. 19112. A statistical study of the influence of moisture and acidity on palatability and fermenta- tion losses of ensiled hay crops. J. Dairy Sci. 35:517. Wyrwicke, W. and C. Dobrzecka. 1960. Relationship between feeding and satiation centers of the hypothalamus. Science 12:805. APPENDIX 85 86 Appendix Table 1. Dry matter losses in stack silos during Trials 1 and 2 (31112;) «gig-gut) Dry matter ensiled (1b.) 20.776 13.256 Dry matter fed out (1b.) , 7.293 ' 6.937 Dry matter losses ($ of input): Spoiled no.1. ' " 31.2 Unaccounta‘ble 22.5 16.5 Total 6h.9 117.7 Appendix Table 2. Dry matter consumption and average daily gains in Trial 1 37 Group Animal Av. initial Av. daily Av. daily Av. daily nmber liveweight gain dry matter In intake/ ‘ intake 100 lb. liveweight (1b.) (1b.) (1b.) (1b.) 1 607 865 1.53 15.0 1.68 1 125 85h 0.59 16.8 1.911 1 126 802 1.97 19.0 2.28 1 131 697 2.25 17.6 2.110 1 13h 657 2.56 17.6 2.52 1 137 581+ 2.16- 15.1 2.10. 1 11.3 50h 1.81. 15.1 2.83 1 138 1:09 0.53 10.6 2.5h 2 608 851 - 0.31 11.8 1.39 2 121 785 1.88 16.6 2.01: 2 129 771 1.72 16.2 2.03 2 132 6110 2.50 111.7 2.16 2 136 613 - 0.28 11.0 1.81 2 139 1173 1.1.1. 11.1 2.21 2 1115 1167 1.53 10.9 2.22 3 609 991 - 0.81, 11.2 1.1h 3 128 821 0.03 11.8 1.10. 3 123 783 0.91 10.8 1.35 3 12h 70h 0.1a 11.3 1.59 3 l35 626 1.19 12.2 1.89 3 1112 527 - 0.62 9.0 1.7!: 3 1111 1190 0.19 8.8 1.78 3 1116 1165 - 0.1.1. . 8.1; 1.83 Appendix Table 3. Dry matter consumption and average daily gdminbnl2 Av. daily In intake/ NOR. unnum s O o o a U o SSREEgfifi 88E§S O O U I O O O 0 0 o I 0 9 0 a 0 O 35¥$BSG8 O owoooooo HyHoyHyH HHHHH. 4H®¢quo mwwmmmmw H aeaaaaus Contact; 5 (1b.) 0 0 O O O O a O I a o o a o I HpmHHHHH HHPHMHHH mm» fi8383$§$ 8&8i8833 £83 Appendix Table 11. Dry matter consumption and average daily gains in‘Trial 3 39 Group Animal Av. initial Av. daily Av. daily Av. daily number liveweight gain. dry matter m intake/ intake 100 1b. liveweight (1b.) (1b.) (1b.) (1b.) 1 135 :.1056 1.38 18.1: 1.68 1 1311 1030 2.18 19.6 1.77 1 lhl 953 2.93 20.8 2.00 1 138 726 1.91 111.1 _. 1.81 l 159 665 1.66 16.1. 2.32 1 157 -660 1.57 15.6 2.21 2 123 1061 3.611 23.5 2.01 2 1&6 979 2.61 19.2 1.82 2 130 93h 2.91 21.5 2.13 2 1119 811 1.80 17.2 1.99 2 161 ‘ “7599 1.50 12.9 2.19 _2 165 367 1.32, 9.5 2.38 3 1113 - 1015 1.89 19.5 1.82 3 ' 11:2 973 2.11 21.0 2.02 3 139 95!: 2.30 17.0 1.72 3 1&5 9116 2.96 21.1 2.0h 3 158 670 1.38 16.2 2.28 3 163 1173 1.07 11.6 2.31 3 166 380 1.111 10.0 2.0 -...‘T'. ~3- 90 Appendix Table 5. Dry matter consumption and average daily gains in Trial h Group Animal Av. initial Av. daily Av. daily Av. daily number liveweight. gain dry nutter _ m intake/ intake , 100 1b. ' _ liveweight (1b.) (1b.) (1b.) (1b.) 1 1511 1201 1.68 20.9 1.71 1 158 890 0.96 19.2 2.12 l 153 . 877 2.68 17.7 1.9% l l59 855 1.95 19.2 2.25 1 166 » 538 2.011 15.5 2.71. l 165 511 2.16 15.2 2.78 l 167 4192 1.6h 15.1 2.511 1 170 589 2.1.3 13.1 3.10 2 1115 1158 2.21 21.5 1.79 2 11.9 973 1.82 19.9 1.99 2 158 8111 1.25 18.0 2.16 2 169 1188 2.61 15.3 2.92 2 168 1138 2.25 11.7 2.19 2 171 576 2 .lll- 12.5 5 .05 II.- ‘I l‘l‘l‘". . V?” ”'HW— . .7 . I... a, :0 & h,~ My; 1 ‘. u 0' 'C 9.1. .o .4 at-.. true: 34..