[JARS ' I ’- III I. ‘-“";,;’I J \ r I 2'41”“: pt- ’1‘!!!" OVERDUE FINES: 25¢ per day per item RETURNING LIBRARY MATERIALS: ——_________- Place in book return to remove charge from circulation records ABSTRACT .A COMBARISON OF SOME.ASPECTS OF THE NUTRITION OF THE ‘WHITE-TAILED DEER AND THE DOMESTIC COW by HA5, fl Henry L: Short 4% FM ,76, /7é 2. Henry L. Short This dissertation reports a first study of rumen fermenta- tion in the Cervidae and compares certain aSpects of deer nutrition with those of a domestic steer. White-tailed deer (Odocoileus virginianus) and a Holstein- Friesian steer were fed a pelleted alfalfa hay-corn concentrate, terminal portions of the reproductive growth of a big-tooth aspen (Pmulus grandidentata) and leaf sprays of white cedar (M occidentalis). Samples of rumen liquor of both animals on the three diets were analyzed in the laboratory to compare (1) the composition and concentration of volatile fatty acids in the rumen material and (2) to qualitatively and quantitatively differentiate the volatile fatty acids and gases of fermentation. For the deer there were 10.88-13.96 milli moles of volatile fatty acid present per 100 ml of rumen liquor on the alfalfa diet, 5.78 milli moles of volatile fatty acid on the aspen diet and 7.68- 8.21 milli moles of volatile fatty acid on the white cedar diet. The level of volatile fatty acids on the alfalfa diet was similar to that determined for the steer but the volatile fatty acid levels on the aspen and white cedar diets were greater than comparable measurements for the steer. The in 11332 fementations of deer rumen liquor produced volatile fatty acid concentrations which on the alfalfa diet were similar to those produced by steer rumen liquor but Henry L. Short which on the aspen and white cedar diets were significantly greater than those produced by steer rumen liquor. Fermentations of deer rumen material produced concentra- tions of gases on the alfalfa diet that were similar to those pro- duced by steer rumen material but on the aspen and white cedar diets deer rumen material produced significantly greater concentrations of gaseous products. In fermentations of deer rumen material the gases formed a greater percentage of the total fermentation products and these fermentation products had a consistently higher calculated oxidation-reduction value than did the products from fermentations of steer rumen liquor. These data suggest that a somewhat more rapid rate of fermentation occurred for in mg incubations of deer rumen material and that a greater synthesis of microbial tissue may have occurred in these incubations. Deer rumen material consistently contained a higher percentage of solid material which may have accounted for some of the increased products of fermentation on the aspen and white cedar diets. The results of the inflzitgg cellulose digestions of solka floc and aspen and white cedar fibers tend to support the hypothesis of a rapid rate of rumen fermentation‘by deer. For the deer the range of cellulose digestion of all fibers was similar, about 6-28%. For the steer solka floc digestion on the alfalfa diet was higher, fiber Henry L. Short digestion on the aspen diet was similar to, and fiber digestion on the white cedar diet was somewhat less than comparable measurements for deer. Appreciable fiber digestion in the rumen requires a long incubation period. However, the presumed rapid fermentation rate within the deer rumen, necessitating a rapid turnover rate of rumen contents may indicate that relatively low fiber digestion is normal for deer. White-tailed deer have a rather high basal metabolic rate and possess a relatively small rumen containing only modest amounts of volatile fatty acids at any one time. Rates of absorption of volatile fatty acids from the rumen and total production of volatile fatty acids in a 21+ hour period have yet to be measured. It seems possible, however, that 2h hour volatile fatty acid production in the rumen may account for up to one-half of the required daily main- tenance energ of deer. It is further suggested that the utilization of microbial tissue may furnish a sizeable portion of the remaining maintenance energy requirement. It is demonstrated that the addition of high energy, easily fermented food stuffs to browse or forage species increases dry matter intake and favorably affects the physio- logical condition of the animal. It is suggested that food items should be evaluated on the ease of fermentation or the rapidity with which they become available to deer as well as their chemical composition. The apparent discrepancies between survival of deer under natural conditions and the results of controlled feeding ‘I Illllllluri Henry L. Short experiments may reflect the inadequacy of present knowledge of deer food habits as deer may select and utilize plant tissue which can be readily made available to them through rumen fermentation. Major differences in the micro-organisms present in the rumen of deer and the steer on the white cedar diet are suggested by the effect of white cedar oils on carbohydrate fermentation. It is hoped that future research studies with deer will further utilize tools that have become conventional in the study of domestic animals as it is felt that these techniques offer great potential to the future management of wild animals. AWISONGFSWJEASMSGFTHENUTRITIONOFTHE WHITE-’EAJIED DEER AND THE WTIC can by w 1 ADA” Henry 1.. Short ATWIS Submitted to Michigan State University in partial mlfillment of the requirements for the degree of mo}! OF PHIIIBOPEY Department of Fisheries and Wildlife WI 4621744,”?«e’ F 24, /752 ACICI‘IWImGM-ITS This dissertation is a tribute to the aid, advice, and confidence of2many persons. I am first and foremost indebted to many members of my family and especially my sister and‘brother-in-law, Dr. and Mrs. Nicholas H. Beecher. ‘Hithout the personal sacrifices of these persons, I would certainly never have had the Opportunity to write this thesis. This research has been a cooperative venture between the Department of Fisheries and Wildlife and the Dairy Department at Michigan State university and the Game Division,.Michigan Department of Conservation. Drs. George.A. Petrides and.Leslie'W. Gysel of the Fisheries and Wildlife Department offered advice and counsel and critically read the manuscript. Dr. Roy S. Emery of the Dairy Department provided the services of a steer equipped with a rumen fistula and kindly loaned laboratory space and equipment. .Mrs. Dorothy Carpenter and several graduate students in the Dairy Department offered advice on several occasions. I am especially indebted to Drs. Ralph.A. MacMullan and L. Dale Fay of the Game Division who arranged for and provided deer, equipment, feed materials, tranSportation and financial assistance. Dr. C. T. Black provided space and facilities at the Rose Lake ii 'Wildlife Research Station and many colleagues at the Rose Lake Station offered assistance in handling and caring for deer. Drs. Rollin H. Baker and John E. Cantlon reviewed the manuscript and generally made my stay at Michigan State University a more pleasant adventure. Drs. R. L. Saleury, formerly of the Department of.Agricultural Chemistry, and Duane E. Ullrey, Depart- ment of Animal Husbandry, offered suggestions and expressed interest throughout the study} Mrs. Helen.Albin of the Fisheries andflWildlife Department kindly kept me informed of proper procedures for graduate students. Finally Miss Cathleen I.Peeke cheerfully offered clerical and typing assistance on many occasions. iii TABLE OF CONTENTS ACKNWIEDGFMENTS............. LISTOFTABLES.............. LISTOFFIGURES............. INTRODUCTION............... LITERATUREREVJIH............ Recent Pertinent Research with Deer. Studies of the Chemical Composition of Deer Foods. The Digestibility by Deer of Browse and Forage Species FoodHabitStudieS.................o Nutritional Requirements Of Deer o o o o o o o o 0 Deer Blood, Vitamin Synthesis and :_i_n_ METHODS................. Description of Feeding Trials. . . . Samples of’Rumen Material. . . . . . Experimental Techniques. . . . . . . RESULTS................. Volatile Fatty.Acids of Fermentation Gases of Fermentation. . . . . . . . Deer Fed on Alfalfa Concentrate Deer Fed on Aspen . . . . . . . iv vitro Studies 11 vi viii \0\o-1\n\nw 13 1h 21 27 3o 31 DeerFedonWhiteCedar. . . . . . . . . . . . . . Steer Fed on Alfalfa Concentrate. . . . . . . . . . SteerFedonAspen. . . .. . . . . . . . . . . . . SteerFed onWhite Cedar. . . . . . . . . . . . . . Redox Measurements from in 15:329. Fermentations. . . Per Cent Solids in Rumen Material . . . . . . . . . Fermentation Balances of in KEEP. Studies. . . . . . . . Rates of in v__i_1_;_1_‘_g Cellulose Digestion. . . . . . . . . . Cellulose Digestion by Steer Rumen Material . . . . Cellulose Digestion by Deer Rumen Material. . . . . Discussion of Cellulose Digestion . . . . . . . . . Energetics in the White-tailed Deer. . . . . . . . . . . Rumen-Body Weight Relationships . . . . . . . . . . Fermentation Products as a Source of Emergy to Deer Rates of Turnover of Rumen Contents in the Deer . . Feeding Trials, Food Intake and Fermentation Rates. Effect of White Cedar on Carbohydrate Digestion. . . . . Discussion of White Cedar Oils and in vitro Fermentations.................. DISCUSSION.......................... Predicting the Digestibility of Food Stuffs. . . . . . . ResearchandManagement................. SUMMARY........................... me CITE O O O O O O O O O O O O O O O O O O O O O O 0 Page Table 10 LIST OF TABLES Page Volatile Fatty Acid Production by Deer Fed OnThI‘GEDietSo0000000000000... 21+ Volatile Fatty Acid Production by a Steer Fed onThreeDiets................. 25 Comparison of Volatile Fatty Acid Production of in vitro Fementations of Three Deer Diets, DeerVersusCow................ 26 Qualitative and Quantitative Analysis of Gases from in vit____r9_ Fementations of Rumen Material ofDeerFeTonThreeDiets..o......e. 31+ Fermentation End Products of Deer Fed on ThreeDiets....o.o........... 3S Qualitative and Quantitative Analysis of Gases from in vitro Fementations of Rumen Material Of aSteer Fed on Three Diets o o o c 9 o o o 0 1+2 Fermentation End Products of a Steer Fed onThreeDiets......o.......... ’43 Fermentation Balance of Gas and Volatile Fatty Acid Products of in vitro Incubations ofDeerRumenquuor..o........... 1‘7 Fermentation Balance of Gas and Volatile Fatty Acid Products of _i_n_ vitro Incubations ofSteerRumenLiquor............. 1‘8 Rates of Cellulose Digestion (Solka Floc and Plant Fibers) of Rumen Material of Deer Fed onThreeDiets................. 55 Rates of Cellulose Digestion (Solka Floc and. Plant Fibers) of Rumen Material of a Steer FedonThreeDietS............... 56 O O I O O I I I 0 o I 0 , . O 0 0 o I v , 9 O o o o c O O O O l I O O O I O o o n I O O O O O I O O I- ‘ I O I C O a Q I O I O O \i \l _.~I Table 13 11+ 15 Page Comparison of the Ranges and the Averages of Cellulose Digestion of Solka Floc and Plant Fibers, Cow versus Deer, Each Fed on ThI‘GGDietSoooo00000000000000 57 Comparative Measurements of Several Rumen- Body Weight Relationships of Domestic Animals and the White-tailed Deer . . . . . . . 6O Basal Metabolism of Deer Compared to that Of Goat, Sheep and Cattle o o o o o o o o e o ’. 7’4- _I_n_ vitro Fementations to Determine Effects of White Cedar upon Carbohydrate Disappearance . 75 vii Figure LIST OF FIGURES .Average Dry Matter Intake of 13 Individual Feeds and.Subsequent Change in.Body Weight Projectedto9ODays. o o o .000 o o oo 0 Effects of Combination Diets and Concentrates upon Dry Matter Intake and subsequent Changes inBodyWeight................ Rates of Disappearance of Soluble Carbo- hydrates from Several ig_vitro Fermentations. viii Page 72 81 INTRODUCTION The present study was a first attempt to study rumen fermentation in the Cervidae. A second objective was the compari- son of certain aspects of the nutrition of the white-tailed deer and the domestic cow. Feeding experiments with a steer and several deer were conducted with three test diets. After a three week adjustment period rumen material was removed from the test-fed animals and analyzed in the laboratory. Several 1.3 _v_i_t_12 fermentations of the rumen material compared the quantity and identity of the various products of fermentation. A second series of _ip_ 11.139 fennentations demonstrated differences in cellulose digestion between the two Species of ruminants. An anatomical study of the deer rumen was undertaken to explain basic differences in the _ip_ vitro fermentations. LITERATUREREVIEH A large literature about deer nutrition and physiolog is rapidly accumulating. Research published to 1955 has been by Walter P. Taylor (1956). The present chapter may be considered a supplement updating and evaluating studies that have been published Since 1955. Studies 93: the Chemical Cmsition 92 Deer Foods Taylor (1956) lists extensive references to the proximal analyses of deer foods. Such determinations of the chemical compo- sition of foods has shown that a major variation in the chemical composition of deer-foods occurs from the growing to the non-growing seasons and that the nutritive value of forages differs with soil conditions. ‘ Hagen (1953) contrasted "good” and "poor" browses on crude protein levels. Bissell andStrong (1955) and Dasmann (1956) utilized crude protein levels as indices of the'forage values of browse species. The New Hampshire workers (Anonymous, 1956) have noted that many browse species only contain about 5% crude protein during the winter season. Such a low level of dietary N suggests that the environment supplies only subsistence energy to the white- tailed deer herd during this season. Gastler (1951) analyzed the chanical composition of deer foods, but could not determine why some plants were palatable and others non-palatable to deer. How- ever, the palatable plants tended to have higher calcium, crude fat, nitrogen free extract and total sugar levels than did the non-palatable species. Smith .e_t all. (1956) believed that inadequate crude protein, phosphorus and cobalt in the browse species of the North Carolina coastal plains was responsible for the unthrifty appearance of the local deer herd. _Th_e_ Digestibility by Deer 9_f_ Browse and Forage Species ' Digestibility coefficients (per cent differences in the chemical composition of feeds and feces) of deer foods have been performed on several occasions. Maynard gt §_l_. (1935) compared the digestibility of alfalfa and an alfalfa-grain mixture, by goats and deer. Generally the digestibility of these foods by deer was somewhat lower. Bissell and Weir (1957) noted little difference in the way sheep and Columbia black-tailed deer (Odocoileus hemionus columbianus) utilized alfalfa, chemise or live oak. Both ruminants utilized alfalfa and chemise distinctly better than they did live oak. Forbes et al. (191:1) compared the digestibility of some foods by deer with published results fran cattle, sheep and goats. Generally similar values were obtained for the four ruminants though deer had somewhat lower capacities to digest crude fiber. For deer the digestibility of a food stuff was inversely dependent on its crude fiber level. AS the per cent crude fiber in hardwood species generally increases during the winter dormancy season most hard- wood browses must have a decreased nutritive value during this critical period. Forbes states that winter browse should be re- garded as supplying critically needed maintenance energy .rather than constituting a highly nutritious ration. Digestion of the protein of browse species varies (Bissell 93 91,, 1955) and Silver and Colovos (1957) found that the digestibility of protein generally was low, but that digesti- bility of the ether extract fraction and. carbohydrates of several browse species was high. Smith (1952 and 1959) performed standard digestive trials with browse species and the wastern mule deer. He states that none of the experimental diets of sagebrush, Juniper and oak seemed to be adequate when compared to recommended allowances for domestic sheep. Smith feels that neither chemical content nor digestibility coefficients are adequate measures of the value of a browse plant to deer. Smith gt 2;. (1956) also used the lignin marker technique to determine the digeStibility of browse plants. They believed the technique of little value to the study of browse speciesand their digestion by mule deer, as results from the lignin ratio method little paralleled those obtained by the more conventional technique. M M Studies Many food habit studies of deer have been made. Very frequently the stomach contents of either road-killed or hunter- collected deer have been analyzed to determine either the plant species eatencor the frequency that a particular browse species has been eaten (Lovaas, 1958). This type of survey complemented by browse surveys that estimate the kinds and amount of food substances available in the environment allow the determination of food prefer- ences (Wilkins, 1957). Changes in food preferences have been correlated with changes in habitat or environment, such as those caused by fire (Biswell, 1961). Food habit studies have also been undertaken to measure the competition between wild and domestic Species as best illustrated in the study of the deer- cattle competition on the King Ranch in Texas (Davis, 1952). Nutritional Requirements 9;: Reg; There is a growing literature about the nutritional requirements and the physiology of deer. Cowan and Wood (1955) and Cowan gt 3., (1957) described the growth curves of young black- tailed deer. By studying animal performance under different feeding regimes these workers described the caloric requirements and the necessary food intake for young and adult deer. Bissell st 31. (1955) calculated the probable caloric requirement for maintenance of the black-tailed deer using the formulae of Brody (1916). These l‘ workers extrapolated extensively from Brody's values on the assumption that metabolism in the rumen of the deer paralleled that in the bovine. Silver 33; 21.1.- (1959) measured the basal metabolism of the white-tailed deer in February and June. Be- cause of the Similarity in the measured values between the two seasons, they Speculated on physiological mechanisms that must have been Operative to compensate for the environmental condi- tions of winter. French 33; 51. (1955a,b; 1956), French _e_t_ g. (1960). Lens 2:2 91. (1959), Magruder 2:6. s1. (1957) and McEwen _e_t_ _a_1_. (1957) report the results of a nutritional study of the white-tailed deer. Growth performances indicated a daily re- quirement of 3600 gross Cal for a deer weighing 50-60 lbs, 6300 gross Cal for a 100 lb deer and 9900 gross Cal for a 150 1b deer. The optimum protein level for growth was 13-16% and calcium and phOSphorus demands were in excess of 0.09% and 0.25% reSpectively. Antler development was positively correlated with the plane of nutrition, and was greatest when calcium and phOSphorus levels were high. Maintenance requirements (caloric and mineral) of adult deer were shown to be considerably less, when expreSsed per unit weight, than those of growing animals. Generally, after reach- ing sexual maturity, decreased food consumption and weight loss occurred every winter regardless of diet. Consumption of food was poorest and weight loss greatest during the rutting season and again in late winter. Protein and mineral requirements decreased during the winter months. These workers suggested that cyclic changes in pelage, antler develOpment, food intake and weight are related to day length. The implication is that under natural conditions the decreased requirements and consumption of foods may be a genetic and physiological adjustment to the normal winter stress period. 2935 §_l_o__od_, Vitamin Synthesis and; _13 vitro Studies Several analyses have been made of deer blood. Haugen and Hove (1960) found no carotenoids in the blood of a limited sample of white-tails from Alabama. These authors also found normal vitamin A levels and. subnormal levels of vitamin E present compared to similar measurements of domestic ruminants. Browman and Sears (1955) summarized several normal blood values of the mule deer and Hilber and Robinson (1958) determined that plasma sodium, chloride, calcium and magnesium levels of the white-tailed deer are not different from those of domestic ruminants. Total plasma cholesterol values were lower than those for either caribou or domestic sheep and goats. Teeri 93 §_l_. (1958) described the blood picture of malnutrition in male white-tailed deer fawns. Teeri 9_t_ 91. (1955) studied the rumen synthesis of several vitamins in the white-tailed deer. Nicotinic acid and riboflavin were little synthesized in the deer but synthesis of thiamine and vitamin 1312 was greater than that experienced with cattle. Little research has been concerned with rumen function in deer, and this organ's importance in supplying energy and nutrients. However, in the last three decades many studies of rumen.physiology in domestic animals have‘been published. much of this work has been summarized in two recent synoptic volumes, .Annison and Lewis (1959) and.Barnett and.Beid (1961). ESpecially important in these studies has been the development of the artifi- cial rumen as a research tool. This igggitgg technique is an attempt within the laboratory to duplicate many rumen conditions. This procedure is useful‘both for studying reactions within the rumen and the digestion of different food substances. METHODS Description 93 _F_‘_c_:_e§_i_ng Trials For the _i_n_ 15332 studies deer and steer rumen materials were analyzed in the laboratory from December 1960 through August 1961. The deer were housed in pens at the Rose Lake Wildlife Experiment Station about eight miles east of East Lansing. Feeding and care of the experimental deer was either done by the author or by Michigan Conservation Department personnel. For the first feeding experiment a white-tailed deer outfitted with a permanent rumen fistula (Short, undated) was utilized. After her accidental death, deer were sacrificed to obtain the rumen material. A 700 lb Holstein-Friesian steer outfitted with a per- manent rumen fistula was used for comparative purposes. This animal was provided by the Dairy Department, Michigan State University, and was housed in the experimental dairy barn. The experimental diets utilized in the feeding experiment consisted of (1) a pelleted mixture of alfalfa and corn, (2) terminal shoots of big tooth aspen (ngy._lus Mdentata) and (3). leaf sprays of white cedar (M occidentalis). Brief descriptions of each of the feeding trials follow. I“! .A‘J 10 A pelleted mixture of alfalfa and corn was fed to compare the fermentation products from a concentrate ration. A ton of this feed contained the following: 1000 lbs sun-cured alfalfa meal, 200 lbs dehydrated alfalfa meal, 780 lbs corn, 20 lbs salt and 0.5 lbs of a premixed trace mineral supplement. The deer (estimated weight 120 lbs) was fed three lbs of pellets per day. The steer (estimated weight 700 lbs) was fed eight lbs of pellets each morning and afternoon. It is believed that these feeding levels represented similar planes of nutrition. Both animals ate this feed readily and appeared in good condition. Big tooth aspen is one of the most plentiful vegetation Species in northern Michigan and throughout many other white-tailed deer ranges. In these areas deer Sometimes cause heavy depredations to the vegetative reproduction of aspen. Reproductive shoots of big tooth aspen were obtained fran a recently clear cut area near Houghton Lake, Missaukee Co. The terminal 2h inches of this material was cut and bound into fagots, each fagot weighing about ten lbs. Deer were fed by Opening a fagot and placing the aspen twigs in a barrel. Thus the deer was able to browse freely upon the aspen. The fistulated deer ate little of this browse, lost much body weight and eventually died during this feeding trial. A three-wear old buck, weighing possibly lhO lbs, 11 was then placed on the aspen diet. He ate the terminal two or three inches of each shoot but still lost 20% of his weight in a one month period. Only rumen material from this deer was utilized in the _i_n_ v_i_._t_r;9_ fermentations reported below. The fistulated steer was fed aspen for about five weeks. The terminal ten inches of the aspen Shoots were ground in a hammer mill. These were offered straight or tapped with diluted molasses. Because the steer refused to eat aspen in any form the milled aspen was force fed through the fistula. It seems very likely that the aspen fed to the steer contained a higher crude fiber content than did the very terminal portions selected at will by the deer. It is possible that some of the differences recorded below in the _1_I_1_ !i_t_r_g_ fermentations reflect this slight difference in diet. This type of feeding error can best be corrected by pelleting the ground browse and feeding the processed material. Considerable compaction occurred within the rumen of the steer. on this diet. Coincident with this condition was a slowed rate of fecal deposition and the appearance of feces as hard pellets. At the termination of the feeding experiment the total rtmen contents were removed, weighed, and a sample of this material oven dried. There was very nearly 16 lbs of dry matter within the rumen, though the average daily food intake was only about 3.1 lbs. Unfortunately no estimate of the per cent dry matter of the aspen twigs was cal- culated. However, Davenport (undated) found that 16 hardwood browse 12 species contained 16-63% dry matter during a comparable season. Using these ranges (#5 and 63% dry matter x 3.1 lbs food intake), values of 1.1+ to 1.95 lbs dry matter intake per day are calculated. Theoretically total dry matter within the rumen divided by daily dry matter food intake gives a ratio indicating the length of time required for material to pass through the rumen. These measurements suggest a turnover period between eight and 11 days for the steer. This very slow rumen fermentation is contrasted by the observation of Belch (1956) that a one and one-half day period may be required for a meal of hay to pass from the rumen. White cedar is considered a valuable and stable element in the diet of deer in many areas of the Great Lakes region. Deer in northern climes often yard in such sheltered terrain as conifer- ous swamps when heavy snow restricts movement. White cedar is often a major vegetation type in these yard locations and is one plant Species that offers sufficient protein and energy in its leaf sprays to maintain deer. The white cedar utilized in these feeding trials was cut in the Dead Stream Swamp, Missaukee county. Two deer were fed on white cedar from May 12 until June 27. There seemed to be differences between the deer regarding their appetite for cedar. One animal in the latter stages of pregnancy ate an estimated two lbs of bark and leafy material daily and midway through the ltO-day feeding period gave birth to two fawns both of which were of subnormal weight. During this feeding period the doe's 13 weight diminished from 126 to 67 lbs. The second deer fed on white cedar was not pregnant and during the 1+7-day feeding period lost about 20% of her weight-“from 150 to 116 lbs although she consumed about three to four lbs of white cedar in a 2h-hour period. The fistulated steer was fed leaf Sprays of white cedar cut from cedar branches. This feeding trial took place from May 1h until June 10 and during this 27 day period the steer lost weight and near the end of the feeding experiment appeared in poor condition. On occasion the steer voluntarily ate small quantities of white cedar though the usual situation involved force feeding through the fistula. Usually food intake for the steer averaged onlythreetofourlbsperdayaswhite cedarwasonlyslowly fermented within the rumen, causing compaction and the formation of fecal pellets. The rumen contents of the steer had the familiar and strong odor of cedar oil. Sgples g: m Material ’ During the early feeding trials a tame white-tailed deer was outfitted with a rumen fistula (Short, undated). After her accidental death in April 1961, feeding trials were conducted with non-domesticated deer that were born in captivity. At pre- scribed periods these deer were collected utilizing the "dart gun" method developed by Crockford (1957). With this technique one-half to one ml (ten-20 mg) of Sucostrin (succinylcholine chloride) was lit injected intramuscularly. A deer was immobilized and died about five minutes after injection. A sacrificed deer was quickly removed to the laboratory where the stomach was exposed, ligated and removed. Blood and all detritus was washed off with warm water, the rumen was punctured and the rumen material strained through a single layer of cheese cloth into clean 500 or 1000 ml plastic bottles. In all instances that rumen material was obtained for laboratory analysis the collection bottles were filled to capacity with rumen liquor to maintain as anacrobic conditions as possible and the filled, capped bottles were immersed in warm water to prevent fluctuations in temperature. Often the rumen liquor was in the laboratory less than one hour after its removal from the deer. Rumen liquor from the steer was collected through the fistula and rapidly transported to the laboratory where it was treated similarly to deer rumen liquor. Experimental Techniques Containers of rumen liquor brought into the laboratory were immediately placed in a water bath at 39°C. A small sample of rumen liquor was removed for acidity determination, using a Beckman Model G pH meter calibrated with a standard pH=7 buffer. A second small sample was removed and examined under the microsc0pe to check the microbial pOpulation present. For the determination of volatile fatty acids in the rumen liquor a third sample of 200 ml 15 was drawn off and centrifuged for about five minutes at inter- mediate Speeds in a Model V International Centrifuge. A 50 ml aliquot of this treated sample was removed and fixed with one m1 of 50% sulfuric acid which killed the rumen micro-organisms present and prevented the further elaboration of fermentation products. This acidified sample was placed in a cooler and was subsequently analyzed for volatile fatty acids of fermentation. Samples of rumen liquors treated in this manner represent the 0 hour level of fermentation products mentioned below. Fermentations of rumen liquor were carried out at 39°C in a 250 m1 Erlenmeyer flask. The Erlenmeyer flask was connected to a gas buret which allowed measurement of gas production. Gas was collected through the displacement. of fluid, slightly acidified so that carbonate would not be precipitated. Fifty m1 of 0.1M phOSphate buffer was added to each Erlenmeyer flask to maintain the Hydrogen ion equilibrium of the system. Control fermentations consisted of 150 ml of strained rumen liquor and 50 ml of phOSphate buffer. These incubations measured the fermentation products formed from the particulate matter carried over in the rumen liquor. Substrate fermentations consisted of 50 ml of buffer, 150 ml of strained rumen fluid and one gm of the feed material (ground to two mm in a Wiley mill). These incubations measured the effect of adding the food material 16 to rumen liquor. The Erlenmeyer flask, buffer solution and feed substrate (when present) were autoclaved for five minutes to wet the substrate prior to the addition of the rumen liquor. The duration of the in vit___rp_ fermentations varied with the rate of gas production as about 15 ml of gas was required for identification. Often sufficient gas was produced in three hours although some fermentations of bovine rumen liquor did not produce sufficient gas in six hours. The gases of fermentation were analyzed for carbon dioxide (cog), methane (cap) and hydrogen (H2). These are the principal gases of fermentation. Carbon dioxide was analyzed by passing a measured sample of gas through a 50% potassium hydroxide solution, which removed the carbon dioxide as carbonate, and noting the difference in amount of gas present. Samples of remaining gas following the passage through the potassium hydroxide solution, were analyzed in a Cenco Vapor Phase Analyzer in combination with a Minneapolis- Honeywell recording unit. A cubic centimeter of gas was injected into the gas phase analyzer and the resulting change in potential was recorded on a moving graph. Different gaseous components were represented as deflections in the base line at different times during the gas analysis and the concentration of gas present in the sample was represented by the magnitude of the base line deflection. The presence and quantitative analysis of methane and 17 hydrogen were determined by injecting known concentrations of these gases into the vapor phase analyzer. Three replicates of both the unknown gases from fermentations and the gases of known concentrations were used in the analysis. Since the unknown gases previously had the carbon dioxide removed the values of hydrogen and methane were corrected to represent percentage of the total gases of fermentation. ‘ At the conclusion of these in m fermentations samples of the incubated liquor were analyzed for acidity (pH) and a so ml aliquot was centrifuged at intermediate speeds, in a calibrated . tube, to determine the percentage of solid material present. The remaining contents of the Erlenmeyer flask were centrifuged and 50 ml of the supernatant was removed and fixed with one :1 of 50% sulfuric acid. These acidified smples of the control and substrate fermentations as well as that of the 0 hour sample were analyzed by column chromatography to determine the volatile fatty acids present. The column chromatographic technique utilized was essentially the method of Wiseman and Irvin (1957). This system utilized a preparation of celite (an analytical filter), distilled acetone, petroleum ether and an indicator dye that was _forced under air pressure into a glass column. A two ml portion of the acidified sample of rumen liquor was forced into the columns and the individual volatile fatty acids were eluted by varying the concentrations of 18 the acetone-petroleum ether solvents. The unknown volatile fatty acids were identified by comparing their passage with those from a standard solution. Volatile fatty acid concentrations were corrected for acid washed out of the chromatographic system by the acetone-ether solvents and the concentration of the individual volatile fatty acids was determined by titrating with a base of known normality. Total volatile fatty acid production of control and substrate fermentations were corrected for the 25% dilution caused by the addition of buffer. Volatile fatty acid concentrations are eXpressed below as mM/lOO ml of rumen contents and as mg of the individual acids. A second series of _i_n_ 313:2 analyses comparing cellulose digestion by deer with that by the steer utilized the techniques of Salsbury _e_t_ EL, (1956) and Salsbury 93 e}.- (1958). Small plastic bags about six inches long were constructed fran one and three- quarter inch Visking ce110phane tubing. The inoculnm of solka floc (a purified wood cellulose) or ground plant fibers (aspen or white cedar) were added to these ceuophane bags so that cellulose would constitute about one per cent of their contents. The ”artificial saliva" mineral solution of Salsbury _e_t_ g._1_. (1956) was utilized. Where possible three replications of each cellulose digestion were made at O, 3, 6, 9,012 and 21+ hours of incubation. Rumen material to be tested and the artificial saliva solution were carbonated by bubbling with carbon dioxide and 19 placed in a 39°C water bath. To each in vitro system 20 ml of the carbonated rumen material was added to the cellulose in the cell0phane bag and 80 ml of carbonated mineral solution was added to a 100 ml wide mouth bottle. The cellOphane bag and its contents of rumen liquor and cellulose were then immersed into the mineral solution, tightly capped and incubated for the desired time period 0 at 39 C. A fermentation was halted at the prescribed time by re- moving the in vitro system from the water bath. The bag was slit and its contents mixed into the mineral solution and frozen. Determination of cellulose digestion involved boiling the contents of the in vi__1_:_r_‘_9_ Jars with concentrated acid. Cellulose digestion was calculated by difference between dry weight of the ample before and after firing in a muffle furnace. As the length of the incubation period of a ample increases the mount of cellu- lose present declines (formed into volatile fatty acids, gases, microbial matter, etc.). The difference in cellulose present at the different hours of incubation compared with that at the 0 hour allows the expression of per cent cellulose digestion. Measurements of rumen capacities were determined for several road-killed deer. These deer were weighed and the stanach ligated and removed. Heights of the rumen contents and the dry weight of rumen contents (after drying for #8 hours at about 85°C) were calculated. The volume of the rumen was determined by measuring the annount of water that could be put into the rumen without causing permanent distention or tearing of the organ. 20 The rates of carbohydrate digestion by deer and the steer on the white cedar diet were measured by the phenol-sulfuric acid method of Dubois gt_ 2.1.- (1956). Control and substrate incubations of rumen material were smpled at hourly or two-hourly intervals and a five ml aliquot was removed. One ml of this aliquot was diluted with water to give carbohydrate concentrations in the range of 10-100 micrograms. These smples treated with phenol and sulfuric acid gave a sensitive, stable, orange-yellow color. The Optical density of the treated smples was read at l+90 millimicrons on a Beckman Spectrophotometer and compared with known values. Because of the small number of replications in the experimental trials it was not possible to analyze the results statistically. Consequently the range of experimental values are listed below and differences are discussed only if the ranges of experimental values do not overlap. These preliminary data must be supplemented with many additional replications to establish normal values of fermentation rates or products for the white- tailed deer. RESUIIL‘S VOIATHE FATTY ACIDS (IF FERMENTATION The fermentation of carbohydrate by rumen micro-organisms can be described as: Total carbohydrate utilized = volatile fatty acid forma- tion + gas formation 4- bacterial protein, fat and polysaccharide formation Much of the utilized carbohydrate results in the formation of volatile fatty acids and gases and these products were analyzed to canpare the fermentations of the three test diets by the steer and the deer. No measurements were made of the synthesis of carbohydrate into microbial protein, fats or polysaccharides. Volatile fatty acid data for the several fermentations of deer and steer rumen liquor are listed in Tables 1 and 2. Table 3 offers a canparison between the deer and the steer of volatile fatty acid concentrations on the three diets. The total concentration of acetic, propionic and butyric acids in deer and steer rumen material on the alfalfa concentrate feed was similar, 10.88-13.96 nut/loo ml for the deer and 11.11-13.10 21 22 mM/lOO ml for the steer. For deer rumen material the butyrate levels were less but propionate levels were greater than comparable values for the steer. The wide range of acetate values masked any difference that might be present with this acid. The high-energy, high-protein alfalfa concentrate diet consistently provided volatile fatty acid values greater than those experienced for the aSpen or white cedar diets. The volatile fatty acid concentration of deer rumen material on the aSpen diet was 5.78 hid/100 ml, a value that was ill-53% of the acid concentration on the alfalfa concentrate. The volatile fatty acid concentration of steer rumen material on the aspen diet was 3.534.56 mM/lOO ml, a value only equal to 264193 of that measured on the alfalfa concentrate. Similar levels of propionate occurred in the rumen material of both Species but greater concentrations of butyrate and acetate were present in deer rumen liquor. Rumen material from the steer fed white cedar contained a volatile fatty acid concentration similar to that observed on the aspen diet, 3.h8-l+.56 mM/lOO ml. Rumen material from deer fed white cedar tested 7.68-8.21 Hid/100 ml. This volatile fatty acid concentration was 55-75% of the level determined for deer rumen liquor on the alfalfa concentrate and was greater than that of steer rumen liquor on both the aspen and white cedar diets and /‘I 23 deer rumen liquor on the aspen diet. Similar butyrate levels were present in the rumen liquor of both species but greater propionate and acetate concentrations were present in deer rumen material. The 0 hour volatile fatty acid concentrations subtracted fran acid concentrations in the control incubation indicates acid production from the fermentation of solids in the strained rumen material. The subtraction of the 0 hour levels from the acid concentration in the substrate fermentation indicates the effect of added food substrate on volatile fatty acid production. Generally increased volatile fatty acid production by substrate fermentations indicates that more easily fermented products are present in the added substrate than in the solids carried over in the control. It is interesting to note, from Table 2, that on the aspen and white cedar diets a major proportion of the total acid production of the steer was acetate. According to Annison and Lewis (1959:60) the proportion of acetate decreases with the ease that a food stuff is fermented in the rumen. Presumably big tooth aspen and white cedar were more easily femented by the deer than by the steer as the prOportion of acetate was lower for the deer. The acidity (pH) of the fermentations is listed in Tables ll and 5. The pH of deer rumen material was slightly lower than that of the steer on the alfalfa pellet diet, was at a similarly pu..rb oil nl-I¢.q4 ...a 111i I-u.:|i k..- uauliud IriJiinJl Q ‘ OtL!) 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Honpooo V nomad 36:. 3:3 soon 0 V 2.65” N:.N Schumann Vm mm.mma mw.H Hoapooo V amino 3.? soon 0 w." mu.m:m Om.m opmapmssm inofi RA Hospooo V 3.38 can? as aoao: as: we aoaoz as: compasses one .53 Ha coax soapopnofioa 5 soaposooaa are, Boa ahead «case. no sea aoosm c .3 soaposoosm Ase/V 33 seems «defies woos o is 8Q someone as, depoa . N 0.3.9.: I. 0-! 551.61. Inky! ‘I 26 Table 3. Comparison of Volatile Fatty Acid Production of _Ig Vitro Fermentations of Three Deer Diets, Deer Versus Cow Alfalfa A5pen White Cedar Bu Pr Ac Bu Pr Ac Bu Pr Ac 0 Hour L* M S M S M S M M Substrate S“ M s M M s M s 5 Control S S S M M S M M S * I. = Range of acid production of deer rumen liquor less than - that of the steer. U) I! Range of acid production of deer rumen liquor similar to that of the steer. ' M = Range of acid production of deer rumen liquor more than that of the steer. 27 high level on the aspen diet and was distinctly lower than that of the steer on the white cedar. Anniaon and Lewis (1959:60) state that variations in pH encourages the proliferation of different micro-organisms which produce the different volatile fatty acids. The decreased rate of fermentation of steer rumen material on the aspen and white cedar diets was accompanied by a decreased daily food intake (described in the feeding trials above), an increased ruminal pH and an increased percentage of acetate present in the VFA fraction. GASES OF FERMENTATION Gases are formed as an end product of carbohydrate fermentation , both _ig 11.19 and in 17.1.3320. The collection and analyzation of gases produced from the _in 3.1-31:2 fermentations of deer and steer rumen materials was discussed in the Methods Section. Only carbon dioxide, hydrogen and. methane were identified in the present study although as discussed by Anniaon and Lewis (1959:152) oxygen, nitrogen, hydrogen sulfide and carbon monoxide are also sometimes present in discernible mounts. Carbon dioxide is nearly a universal end product of rumen microbial fermentation but the reactions giving rise to methane are more specialized and less well understood. The rumen and artificial 28 rumen are actively reducing systems possessing a variety of hydrogenasea and an abundance of carbon dioxide. Under such con- ditions methane arises through the reduction of carbon dioxide by a.hydrogen donor. Hydrogen and possibly formate and acetate act as such reducing agents within the rumen (Anniaon and.Lewis, 1959:153). ‘As methane production depends on the reduction of carbon dioxide there is a positive correlation between the levels of the two gases. The presence of hydrogen within the rumen or in vitro system.is presumably as a transient, very active intermediary. The conditions under which this gas is formed as an end product of fermentation are not well understood. In the present comparison of the rumen micrdbial fermenta- tion of a domestic and wild ruminant some insight can be gained by the application of fermentation balances. The work of‘Wolin (1960) allows the calculation of theoretical fermentation balances. Such calculations allow a prediction of carbon dioxide and methane pro- duction from the molar distribution of volatile fatty acids present. Helin's calculations are based on the solving of two simultaneous equations. The first equation demands an equivalence between the moles of compounds produced containing two carbon atoms and the moles of compounds produced containing a single carbon atom. The second equation equilibrates the oxidation level of the fermentation products and the oxidation level of the substrate. 29 The 0 hour volatile fatty acid levels of the several _i_r_1_ 11.212. incubations and the volatile fatty acid values obtained when the 0 hour levels were subtracted from the control and substrate fermentations are listed as per cent molar distributions in Tables 5 and 7. In Table l, a negative value for the mount of acetate formed on one control fermentation on the white cedar diet was recorded. In Table 2 negative values of at least one volatile fatty acid were shown fOr one control and one substrate fermenta- tion on the aspen diet and both control and one substrate incubation on the white cedar diet. No fermentation balances could be calculated for these anomalous situations, using Volin's’ formulae. The milli moles of carbon dioxide and methane per 100 ml of rumen liquor are recorded in Tables 1+ and. 6. The diet and fer- mentation as well as the acidity (pH), the per cent solids, the miration of the fermentation, the total gas produced and the hourly gas production per unit of solids are recorded in Tables 1+ and 6. The molar distribution of the acids of fermentation varies with the acidity of the system, the type of fermentation and the feeding regime. The interaction of the end products of a fermentation is as yet inadequately understood though Wolin'a balances predict the relationship between carbon dioxide and methane from the relative distribution of the acids of fermentation. For exmple , empirical observations show that a rise in the acetate present causes a rise I‘ 1“ 30 in the methane level and. a decrease in acetate accmpanied by an increase in propionate lowers the methane level. Increased butyrate levels are accompanied with increased levels of carbon flande o MEI Leg _o_n_ Alfalfa Concentrate TwO fermentations were conducted with rumen materials from the deer fed alfalfa concentrate, however, on only one instance was data about gas production collected. The rumen material of this fermentation contained a very high per cent of solids, a low pH and produced a large quantity of acid. The molar distribution of acids of the substrate fermentation compared with the 0 hour fermentation showed slightly decreased concentrations of acetate and prOpionate and an increase in butyrate. Holin's fermentation balance predicted a rise in carbon dioxide and no appreciable change in methane as compared with the 0 hour predicted values. Data in Table h show that 25.16 mM of carbon dioxide and b.27 all of methane were produced giving a wide carbon dioxide- methane ratio of about 6. Compared to other fermentations sumarized in Table h, where frequently a carbon dioxide-methane ratio of 2 to It exists, this was a high production of methane and an exceptionally high production of carbon dioxide. It is possible that a wide carbon dioxide-methane ratio exists in this instance because carbon dioxide was produced in abundance but insufficient hydrogen donors 31 were present to accomplish the reduction to methane. The presence of free hydrogen in this fermentation suggests that something, possibly the rather low pH, did not allow the utilization of this very active intermediary. The control fermentation contained an abundance of solids in the rumen material, produced rather large volatile fatty acid levels and had a final pH only slightly higher than did the unincu- bated rumen material. Table ’4 shows that free hydrogen (possibly again related to the low pH of this fermentation) was detected, and Table 5 shows a sharp decrease in propionate and an increase in buWrate occurred. Wolin's equations predict a slightly increased methane production compared to the substrate fermentation and a slightly decreased carbon dioxide-methane ratio. From Table h, 16.33 m of carbon dioxide and LS7 nM of methane (slightly greater than the methane produced in the substrate fermentation) were pro- duced. The ratio 3.58 was less than that of the substrate (as predicted by the fermentation balance) and of the same order of magnitude as that produced by fermentations of deer rumen material on other diets . Deer {ed on Asgen The acidity of the rumen material was lower and the acid production decreased on the aspen diet compared with the other feeding trials. The per cent solids in the aspen substrate fermenta- 32 tion was less than that experienced for the alfalfa concentrate but similar to that measured on one white cedar trial. In the aspen substrate fermentation the concentrations of acetate and propionate were slightly lower and that of butyrate slightly increased compared to the 0 hour levels. Under these conditions Holin's equations pre- dict slightly increased carbon dioxide and methane levels with a narrow ratio and this situation was realized as 1+.79 mM of carbon dioxide and 2.03 mM of methane were produced, giving a ratio of 2.37. About 70% of the gas production in this fermentation occurred in the first 30 minutes and it is indicated below that cellulose digestion occurred slowly. These data suggest that the small amount of soluble and easily fermented carbohydrates within the substrate were quickly utilized and then the more refractive materials were slowly fermented. In the control fermentation the percentage of solids present was lower, pH was higher and. the total acids produced lower than on any other fermentation with deer rumen material. Acetate and prOpionate production was decreased and butyrate production increased compared to the 0 hour level, producing an increased concentration of carbon dioxide and an increased ratio. Actually only 1.17 mM of carbon dioxide and only 0.07 mM of methane was produced giving a very wide ratio of 17.60. Also present in this fermentation was 0.20 mM of hydrogen. Presumably the solids within the rumen liquor were nearly refractive to microbial action resulting 33 in little volatile fatty acid formation and a limited gas production of unusual composition. It is interesting to speculate upon the effect of the rather abnormally high pH on both the production of carbon dioxide and its reduction to methane in the presence of hydrogen. 239;: £29 93 White Cedar Fermentations of rumen material from two deer fed on white cedar were conducted. Rumen material from the first deer had a somewhat higher pH, though not satisfactorily measured -- a sanewhat higher percentage of solids and as determined fran total gas and volatile fatty acid production a fermentation rate that was greater than the second deer. For rumen material frun the first deer the acid concentration of the substrate incubation showed decreased acetate and increased butyrate as canpared with the 0 hour acid distribution suggesting a rather wide gas ratio. However, only a ratio of 2.1h was determined. The heavy solids in the control fermentation produced acids in a rather similar propor- tion to that found in the substrate incubation and Volin's equations predict a similar carbon dioxide to methane ratio. However, 1.70 m of carbon dioxide and 0.h9 nM of methane were produced, giving a ratio of 3A2. Possibly the discrepancies between the calculated and predicted gas ratio represent an error in the differentiation of volatile fatty acids produced in these fermentations . 3h 64 0.00 r. 0 00.0 00..." 00.0 0 04.0 38.008 V m 00.0 0.8 e . u. 00.0H 00.0 0a..." 0 00.0 H8080 V .5 0.0: m .0500: $0 003 00.0 0 00.0 3803:... 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Wolin's formulae predict a wide ratio under these circumstances and this was authenticated as a very low production of carbon dioxide, 3.33 mM, was accompanied by a low production of methane, 1.08 mM. Steer Fed 9_n_ Alfalfa Concentrate On only one fermentation of steer rumen material from the alfalfa concentrate diet were gases differentiated and measured” Volatile fatty acid production of both the substrate and control fermentations were slightly less for the steer than for the deer. Both the substrate and the control fermentations produced decreased acetate and increased prOpionate and butyrate levels and increased carbon 0100000000000 ratios compared to the 0 hour level. The total gas production of these fermentations was less than that of corresponding fermentations of deer rumen material and the carbon dioxide-methane ratio was less than that of the deer substrate fermentation but greater than the deer control incubation. As with deer rumen material a rather low rumen pH was encountered and hydrogen was present in the gaseous products of the substrate fermentation. Steer Fed 92 A5pen The difficulties encountered in the aSpen feeding trial 37 have already been related. Rumen material, on this diet, when strained through a single layer of cheese cloth appeared as a brown, bland smelling, very watery sample which contained a very low percentage of solids (from Tables 6 and 7, only 1.5-1.7553). This water-like sample produced insufficient gas for analysis in either control fermentation. For both control and one substrate fermentation at least one of the volatile fatty acids occurred in diminished concentration compared to the 0 hour level so that Wolin's equations could be applied only to one substrate fermenta- tion. The pH of the rumen material was high, greater than 7 for both control incubations and near 7 for both 0 hour fermentations. The molar distribution of acids for the one substrate fermentation showed a slight increase in acetate to a very high level and a rise in butyrate coupled with a decrease in prOpionate, suggested a narrow carbon dioxide-methane ratio. However, rather wide ratios were observed. Presumably the difference is related to a small production of carbon dioxide and rumen conditions which did not favor the subsequent reduction to methane. Etnpirically Wolin's equations, based only on final molar distribution of volatile fatty acids lack provisions for anomalous rates of fermentation and re- sulting extraordinary conditions within the rumen of the animal. Steer fed 93 White Cedar White cedar was treated differently by the two species of ruminants. Acid and gas production as measures of fermentation I" I. 38 activity have shown that deer utilize white cedar fairly readily. A comparison of Tables 1 and 2 shows that acid production by control and substrate fermentations as well as the total concentra- tion of volatile fatty acids within samples of rumen material tended to be greater for the deer. A later section elaborates on large differences in the rates of glucose disappearance from rumen material of deer and the steer. The levels of individual. volatile fatty acids present at the end of the experimental fermentation were sanetimes less than those present at the 0 hour and thus it was not possible to use Holin ' 3 equations for one substrate fermentation or both control ' incubations. It is interesting to note that at the end of one control fermentation the volatile fatty acid level present was less than at the 0 hour. This small difference may either indicate the degree of replicability of the column chromatographic technique or that sme volatile fatty acids originally present may have been metabolized by the microbial papulation with the subsequent production of gas. For the one substrate fermentation where it was possible to apply Wolin‘s equations the acetate and butyrate levels were depressed and the propionate greatly increased and an increased gas ratio, compared to the 0 hour value, was predicted. Actually a very wide ratio of 8.61; was produced. The control fermentation which con- tained. less volatile fatty acid than present at the 0 hour produced small. amounts of carbon dioxide and a wide ratio of about 7.6. 39 M Measurements £39m _I_n_ 11.330 Fementations The application of Wolin's fermentation balances, points up an interesting difference between the _i_n_ M fermentations of deer and steer rumen material. One of Uolin's simultaneous equa- tions involves the equilibration of the oxidation level of the products of fermentation with the oxidation level of the substrate. The redox (oxidation-reduction) values calculated from the milli moles of fermentation products, are greater for the deer than for the steer (Tables 8 and 9). The meaning of redox levels to the rumen or to an E 3.1532. system is not entirely understood but Barnett and Reid (1961:13) suggest that the value may serve as a criterion of micro-biological activity. Thus the high redox level associated with the fermentations of deer rumen material may indicate a high fermentation rate presumably coupled with a large production of microbial tissue. 20:. 2.0.1:. sell-Is .19. Rmen Material. A second basic difference between the fermentations of deer and steer rumen material was the percentage of solids. A comparison of Table ’4 and Table 6 indicates that in nearly every instance the solids in the rumen material fran the deer were at least twice as great as those from the steer. Bovine rumen liquor often had a semi-liquid consistency while deer rumen liquor usually contained numerous particulate matter that made microscOpic observation difficult. Rumen liquor 1+0 seemed to vary in the case with which centrifugation precipitated suspended materials. For example, one sample of deer rumen material fran the white cedar diet was not precipitated even after extensive centrifugation. In Tables h and 5 these per cent solids are simply listed as "heavy" to indicate that they seemed more extensive than that for the second deer fed white cedar. The addition of one ml of 50% sulfuric acid, which killed the organisms present in the rumen liquor and changed the pH of the material, aided in the precipitation of suspended particles. The addition of acid to all samples, before centrifugation, might increase the precision of expressing fermentation products on the basis of solids present in the rumen material. The process of rumination reduces the size of food particles and rumen micro-organisms affect their action upon the surface of these particles. To determine the relationship be- tween the solid suspensions in lumen liquor and the rates of micro- bial fermentation total gas production and total acid production have been expressed as ml gas/unit solid/hour in Tables 3+ and 6 and as 0M acid/unit solid/hour in Tables 5 and 7. For all the control fermentations of deer rumen material gas production, per unit solid per hour averaged 0.8 ml and ranged between 0.6 and 1.1 ml. For the substrate fermentations the average hourly gas production per unit of solids was 1.1 ml and ranged be- tween 0.9 and 1.6 ml. For the control fermentations the hourly acid pro 0.0. fer. tio due 0.C ave per PI‘C ave the prc hr of 01‘ Vol fec‘ 1+1 production per unit of solids averaged 0.05 mM and ranged between 0.03 and 0.06 nM. Comparable measurements for the substrate fermentations were 0.05 and 0.05 to 0.06 nM. For all the control fermentations of steer rumen material the gas production per unit solid per hour averaged 1.1 m1 and ranged between 0.1» and 2.5 ml. The data for the substrate incuba- tions averaged 1.1; m1 and ranged from 0.8 to 3.20 ml. Acid pro- duction from control fermentations of steer rumen material averaged 0.08 nM and ranged 0.03 to 0.21 nM and from substrate incubation averaged 0.09 nM and ranged frcm 0.03 to 0.23 nM per unit solid per hour. Rumen material from the steer produced fermentation products which when expressed per unit solid per hour consistently averaged greater than did comparable data from the deer. However, the wide range of such values fran steer rumen material overlapped production values of deer rumen material so that these differences probably were not significant. Interestingly the larger averages of fermentation products by steer rumen liquor are provided by one or two very productive incubations -- the first fermentation with alfalfa pellets and the first fermentation with white cedar. A possible explanation of the wide variations in gas and volatile fatty acid production by _ig v__i_t_r_‘_9_ fermentations of steer rumen material may be found in the feeding trials. 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Annison and Lewis (1959:1h9) point out that intermittent feeding tends to maintain the stability of rumen conditions while the presentation of food once or twice daily accentuates changes in the concentration of rumen metabolites. Thus sampling of steer rumen material at irregular periods following the ingestion of food might account for the wide variations in the elaboration of products of fermentation. FERMEINTATION BAIANCES 0F _ILN_ VITRO STUDIES The milligrams of volatile fatty acids and gases produced from the in vitro fermentations are listed in Table 8 for the deer and Table 9 for the steer. These listings allow the comparison of the total fermentation products of the several _in _v_i_1_:_r_'_q fermenta- tions, the ratio of gases to total fermentation products and measure the effect of adding different substrates to control fermentations. The total gas and volatile fatty acid products for the deer and steer on the alfalfa concentrate diet were of the same order of magnitude for comparable incubations. However, the total products of fementation from all the in _vi_t_r_9_ incubations of deer rumen material on the aSpen and white cedar diets were greater than comparable values from steer rumen liquor. For both species, the total. fementation products on the alfalfa pellets were greater 1&5 than the fermentation products formed on the aspen or white cedar diets. The increase in milligrams of fermentation products in the substrate incubations was similar for both the deer and steer on the alfalfa concentrate and aspen fermentations. Rumen material from the steer fed white cedar gave negative total fermentation products on both control incubation but the increase in fermentation products on the substrate incubations was greater than that experi- enced with incubations of deer rumen material. Presumably the total production of volatile fatty acids and gases of fermentation show that the alfalfa concentrate was utilized with similar efficiency by'both ruminants but that the deer utilized aSpen and.white cedar more successfully. A comparison of Tables 8 and 9 shows that gases form a higher percentage of the total fermentation products for the deer than they do for the steer. The percentage of gas in a fermentation is dependent on the amount of acetate or'bacterial protoplasm formed in relation to the lactic or propionic acid production. It is tempting to view the increased gas production with fermentations of deer rumen material as reflecting an increased rate of microbial synthesis. This greater gas production for fermentations of deer rumen material also accounts for much of the increased redox.value of deer rumen material which is believed indicative of microbial synthesis. 1+6 The redox values of the substrate incubations of both animals is greater than that of the control fermentations. This higher redox level reflects the oxidized state of carbon as carbon dioxide and the higher molecular weight of this gas is reSponsible for a portion of the increased ratio of gases to total products of fermentation in the substrate incubation. A comparison of Tables 5 and 7 shows that more milli moles of methane were formed by the fermentation of rumen material from the deer than from the steer and this is reflected in lower carbon dioxide-methane ratios for deer rumen material. Presumably these data reflect an active fermentation with a large proliferation of carbon dioxide and a large subsequent reduction of this gas to methane. A brief resume of these i_n _vi’grg fermentations lists four outstanding but interrelated points that should be stressed. First, fermentations of deer rumen material generally formed more milli moles of gas and volatile fatty acids than did fermentations with steer rumen material. Secondly the fermentation products of the incubations with deer rumen liquor had a higher calculated redox level. Thirdly the concentration of gas was a greater percentage of the products of fermentation of deer rumen liquor than it was of incubations of. steer rumen liquor. Finally deer rumen material con- tained a higher per cent of solid material which may account for some of the increased products of fermentaticm. However, in summary, it l I. -1 rklyia...ll,- {In}- t- n . 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This study was undertaken in deference to the much quoted observa- tion, "the digestion of dietary cellulose is the major function of the rumen" (Anniaon and Lewis, 1959:19). The techniques utilized in these experiments are described in the Methods Section. The artificial saliva mineral solution suggested by Salsbury _e_t gl_. (1956) was assumed as applicable to deer as to bovine fermentations. This mineral solution is one of a series (others are listed by Barnett and Reid, 1961:1tl-h2) that has been found applicable for in £13.32 fermentations of sheep and cow rumen liquors. The semi- permeable membrane type of artificial rumen utilized in this in 11.1139. study has been shown to give results similar to those of other applicable apparati (El-Shazly, 33 9.1.: , 1960). The innoculum used in these fermentations consisted of solka floc (a purified wood cellulose) and the ground plant fibers of the test diets. The rates of cellulose digestion are listed in Table 10 for deer and in Table 11 for the steer. Deer rumen material for 50 the aspen and white cedar experiments was obtained at the same time and. from the same animal as was that utilized in the in vitro incubations to determine the products of fermentation (Tables 1 and h). For both experiments with deer rumen material from the white cedar diet the average and range of cellulose digestion is determined from only two replicates at each time interval. The limited contents of these rumen precluded the possibility of larger replications. Most other determinations of cellulose digestion in Tables 10 and ll consist of three replications. Cellulose is considered to be readily degraded by mixed cultures of rumen organisms although incubation for long periods of time (from 20 to 60 hours or more) is often required. In these experiments incubations were carried only to 21+ hours as many studies, for example Salsbury gt gl_. (1958) have shown very appreciable 214 hour digestions. Cellulose d_._igestions by §_’_c_e_e_r_'_ M material Steer rumen material from the alfalfa concentrate digested solka floc at a slow rate that averaged only about 8% at 12 hours. hiring the second 12 hour period the rate of digestion increased so that by 2h hours 1+O%-60% digestion had occurred. These are the greatest values recorded in any of the cellulose digestion experiments 51 with either species. The slow initial digestion of solka floc has also been reported by Salsbury _e_t _a_l_. (1958) who suggests that this early lag in digestion may be related to an initial resistance of solka floc to micrdbial attack. The total digestion was not low as Barnett and Reid (1961:1h5) report data that demonstrate that a high content of grain in the diet reduces cellulose digestion. The alfalfa concentrate consisted of about three parts hay to two parts grain. Steer rumen material from the aspen diet digested solka floc slowly so that at 12 hours digestion was only 2-5 per cent and at 21+ hours only 7-26 per cent. The digestion of aspen fibers began noticeably faster than did solka floc digestion and the 6, 9 and 12 hour average values were greater than for solka floc digestion on either the aSpen or alfalfa pellet diets. The 2h hour values were 26-28%, not significantly different from those of solka floc on the aspen diet, but significantly less than solka floc on the alfalfa pellet diet. The rate of digestion of aspen fiber, if plotted graphically, appears to be roughly linear as opposed to the more sigmoid shaped curves experienced with solka floc digestion on the aspen and.alfa1fa diets. These data suggest that the cellulolytic components of aspen may'be more quickly attacked by the rumen microbial pOpulation. Rather anomalous cellulose digestion occurred when the steer was fed.white cedar as solka floc digestion averaged 2-h% 52 at three hours and only 5% at 21+ hours. The 2h hour values were the lowest determined for any fermentation by either ruminant as solka floc in these experiments seemed essentially refractive to microbial attack. The digestion of white cedar fiber was essentially complete at 3 hours and generally white cedar fiber digestion was greater than that of solka floc although the ranges were not differ- ent o Cellulose digestion by deer rumen material Solka floc‘digestion by deer rumen material from the alfalfa concentrate diet was similar to comparable measurements by steer rumen material for about 9 hours. However, at 12 and 2} hours differences were evident as solka floc digestion by deer rumen material was h-5% and l2-23% while solka floc digestion by steer rumen material was 8% and h0-60‘70. Deer solka floc digestion on the aspen diet was negligible in the first 12 hour period and the averages during this period were lower than comparable ones for the steer and those for the deer on the alfalfa diet. The average and the ranges of solka floc digestion at 21+ hours were similar for both the steer and deer and as was the case with the steer if the values of solka floc digestion for the alfalfa and. aspen diets are plotted graphically they suggest the first portion of a sigmoid curve. The digestion of aspen fibers by deer rumen material aver- aged, in every instance, greater than did the digestion of sollia 53 floc and as recorded for the steer, this curve of digestion appears more nearly linear than sigmoid. Cellulose digestion by deer rumen material on the white cedar diet differed markedly from that recorded for the steer as the average digestion of solka floc was in every instance greater for the deer. The initial rate of solka floc digestion was not slow, as it was on the alfalfa or aspen diets for deer, or on all three diets for the steer. At 3 hours solka floc digestion was 8-10% and at 2h hours 948%. The digestion of white cedar fiber by deer rumen material produced two rather different fermentations -- in one the total digestion was essentially canpleted at the end of 3 hours while the second fermentation showed no appreciable digestion within the first 12 hours. The final 2h hour levels of both the slow and rapid fermentation had a range of values greater than that of the steer on white cedar fiber. Discussion of cellulose digestion A portion of the determination of cellulose digestion involved boiling the sample with concentrated nitric and acetic acids . The residue is termed cellulose though there is no inference that the solka floc or aspen and white cedar fibers are identical so that this chemical treatment allows the discussion of microbial digestion of three different crude fibers by the two species of ruminants. For the deer, the range of solka floc digestion on all diets and cellulose digestion of aspen and white cedar fibers overlapped, 51+ indicating that there were no significant differences present. The results of 2% hour cellulose digestion, by steer rumen material, indicated that significant differences existed between solka floc digestion on different diets and between aspen and white cedar fibers. Steer rumen material from the alfalfa diet digested solka floc at the greatest rate experienced in any of the in v_i_t_r;c_> studies. Steer rumen material digested aspen fiber at a rate that was greater than that of solka floc or white cedar fiber or the rates at which deer rumen material digested solka floc on the aspen diet or white cedar fiber. The digestion of white cedar fiber by steer rumen material was so depressed that it was exceeded by two cellulose di- gestions by the deer -- white cedar and solka floc on the alfalfa diet. An explanation of the low white cedar fiber digestion by steer rumen material is presented in a later section. A ready comparison of the ranges and averages of cellulose digestion, deer versus steer, is provided in Table 12. There are a number of interesting points to be made from these data if the experimental procedures can be satisfactorily applied to the two species. The 21+ hour digestion of cellulose in many instances was less for the deer than for the steer although similar samples of deer rumen material produced greater total gas and volatile fatty acid levels in i3 y_i_t_r_g_ fermentations than did steer rumen material. Unfortunately these data do not indicate whether or not longer fermentations would have increased the total 5 5 moofivmcflanmpoo m Mo owshm>< .n mooapssflspopod m mo owsao><. .s aims-86 semi ma; -86 n36 R6 -86 n86 86 n86 36 -86 84 assoc than: aim-El. n86 88 aim nmod mead-mod. n86 8.38:6 n8;- 8.ma-8.m n8.» 82 sol-mom Ema-mo.m h86a mafia-86 hand 8.8-8.3 n83: 8.5%} n84” dams-mm; 9822 store than: 8.8-8.2 n6.8a Sim-86 penned main-Se. 95.2 5.3 98.2 Sin-86 95.9.. 8E 38 . 88 than: 688-88 all: 8. m- 6 2.4 $15-86 mmfi mil-786 34H 8. m- 6 81m soars. magma-:6 8.8 8. m- 6 86 86 86 v 86 86 mm. m- 6 Hmé 8.8 sfiom :0 ad a 8.8-8.8 5.8 88 -86 86 88 -mm.a and: mo.m -E...n seal” 86 n86 8E nfiom 8.mm-d-.am om.mm Sé -8.H 8.: .36 -mm6 ens mm; -mo.-n 9:4 34 £32" p.34 83 got .88 amass: omqmm 9m><. owssm mm><_ uwssm mw><_ oqum qm><. owdsm swam. opsapmpsm mhsom am mason NH mason m- mason m mhsom my use pawn and moopmoman omoasadoo Home Mom human mouse no not soon so donates: steam no Antonia p83 has 8E 383 838mg smog-Q8 no steam 6H tapas magma 0.0-HEB .. 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Comparison of the Ranges and the Averages of Cellulose Digestion of Solka Floc and Plant Fibers, Steer Versus Deer, Each Fed on Three Diets Hour of Incubation Diet and Substrate 3 6 9 12 2h Alfalfa Concentrate Solka Floc Average 8* S S M M Range S" S S S M Aspen Solka Floc Average M M M M 3 Range S M S S S Aspen Average S S S M M Range 3 s s M ' s White Cedar Solka Floc Average L L L L L Range S S S S S White Cedar Average S S S M L Range S S S M L L = Cellulose digestion of steer rumen liquor less than that of the deer. *S = Cellulose digestion of steer rumen liquor similar to that of - the deer. Cellulose digestion of steer rumen liquor more than that of the deer. M 58 cellulose digestion or minimized differences that occurred in replicate fermentations. It is inviting, however, to speculate upon these variations in cellulose digestion as representing an inter-Specific difference. Pertinent literature that support or detract from the hypothesis that deer digest cellulose less well than do bovine are meager. Forbes et_§l. (l9hl) compared digestibility data from deer with published results of digestibility trials with cattle, sheep and goats. The capacity of the four ruminants to digest feed stuffs in general, including crude fiber, was of the same order of efficiency. However, the most flagrant of the minor Specific differences present was that the white-tailed deer had a lower coefficient of digestibility for crude fiber. These authors showed that for deer the relative nutrient value of several browse Species was correlated with the crude fiber levels of the plant materials. Evidence suggesting a more rapid rate of fermentation in the rumen of deer’has'been presented in an earlier chapter and evidence included'below indicates that this high fermentation rate must be accompanied by a high turnover rate of rumen contents. It has been pointed out previously that cellulose digestion is a time consuming process and the generally slow rate of cellulose digestion by deer may indicate that crude fiber is not a readily available source of energy to deer. 59 ENERGE'I'ICS IN THE WHITE-TAHED DEER A comparison of several rumen body-weight measurements of the white-tailed deer and some domestic animals is listed in Table 13. Such a comparison is warranted as large differences in food habits occur between domestic and wild ruminants and large differences in basal metabolic rates occur between large and small animals. The data listed in Table 13 are summarized from several sources. The generalized body weights for cows and sheep are estimated and the volume of the rumen of these animals is described by Sisson and Grossman (1953). Many of the other descriptive ratios for the cow are average values determined from two groups of hay fed cows, reported by Thomas gt §_l_. (1961). Data of rumen volume in the goat may not be comparable and possibly should not be included in this Table as Tamate (1957) was studying the development of the digestive tract in post-weaning goats and his data only extend to 68 days of age. On many instances pertinent data for the sheep and the goat are not available in the literature. Data for the deer are from the present study. Rumen-Body Weight Relationships The cow has a very capacious stomach, loo-250 liters, depending on the size of the animal. The weight of the material ‘A A a . t \ ~ ” " n \. 4 N . K ../ \_. \ . .- .- . ~ 4\ . t . r- v . . v \ a -. r~ , . I \ i c / A .‘ - . _ \ z s . r l .. s . , a ._ O ‘ . x . I ‘ v . -r... .. o ,— ’ \' ‘ ‘ a . l l , ‘ '._u - c \ / ‘ * — ' l \, r . fl ‘« , g , Table 13. 6O Comparative Measurements of Several Rumen-Body Weight Relation- ships of Domestic.Animals and the'White-tailed Deer Cow Sheep Goat DeerS Body Weight (Kilograms) 600 1+5 3'2'7°5h h0.5-9O Rumen Volume (Liters) 1501 151 3h 2.240(2) Wt. Rumen Contents (Kilograms) 852 1-h,h Wt. Rumen Contents % Body”Wt.) 12.91-13.003 2.5-6.8 Dry Wt. Contents (% Rumen Ht.) 11.13-13.083 7.1-19.9 (fir) BOdy Wt.) loh3"lo683 003u-1039 Centrifuged Sediment 10.1193 5-25 Total Volatile Fatty Acids ' (um/m1.) 112.34.15.63 65.5-182.3 Notes: 1. Sisson, Septimus and J. D. Grossman. 1953. The anatomy of the domestic animals. ‘W. B. Saunders Co., Philadelphia. 972 pp. 2. ‘Weight of rumen contents from data of Hale, gt El.) reported by Barnett and Reid (1961:37). 3. Thomas, J. W., J. R. Ingalls, M. Yang and.B. S. Reddy. Effect of ad_1ibitum.or equalized feeding of alfalfa hay or silage on rumen contents and its characteristics. (Paper read‘before.Amer. Dairy Sci. Assoc. Univ. of wise., Madison, June 12-1h, 1961). h.‘ Tamate, H. 1957. The anatomical studies of the stomach of the goat. II. The post-natal changes in the capacities and the relative sizes of the four divisions of the stomach. Tohuku Journal of.Agric. Res., Vol. VIII, 2:65-77. 5. Data for deer summarized from several portions of the present study. 61 within the rumen is about 10-15% of the weight of the entire animal and the weight of the dry matter within the rumen is about 1.5% of the total body weight. The amount of centrifuged sediment (per cent solids of the strained rumen liquor) was very variable in my study (1.5 to 7%, Table 6) and averaged about 10% in the data of Thomas 23; _a_l_. (1961). Total volatile fattyacid pro- duction was 3h.8 to 131 uM/ml for the steer on the deer diets and about 110-115 uM/ml from the data of Table 13. The data for the deer although quite variable and com- prising only about 10 different animals demonstrates that the rumen volume is only about one-tenth the weight of the animal. A comparable ratio in the cow is about one-fourth. The weight of the rumen contents about 2.5-71. of the body weight is also considerably lower for the deer. The dry weight of the rumen contents ranged from 7.09 to 19.86% and averages 15.8% of the rumen weight. Even though the per cent solids in deer rumen liquor is greater the dry weight of the rumen contents is a smaller prOportion of the deer's body weight. The per cent solids in the rumen liquor and the con- centration of volatile fatty acids were greater for the deer than for the fistulated steer. Unfortunately, it is not possible to compare such data from the deer with those from similarly sized domestic nnninants as the goat or sheep. 62 Fermentation Products _a_.s; g._ m 2: Em pg 922! It is frequently assumed that the energy requirement of homiothemic animals is related to the three-fourths power of their weight (Crampton, 1956:129). So that the metabolism of small animals is greater than that of larger animals when expressed per unit of body weight. This relationship between three domestic ruminants and the white-tailed deer is verified in Table 1h, published by Silver 9.1; _a_l_. (1959). Generally the basal metabolic rate of the deer is very similar to that of the Sheep and considerably less than the much larger cow and steer. Explanations for the relative- ly lower basal metabolic rate of the smaller goat are not immediately obvious. In the ruminant web of the dietary carbohydrate is fermented to volatile fatty acids which are utilized via the citric acid cycle to supply energy to the animal. Annison and Lewis (1959:1hh), for instance, quote data showing that at least 600-1200 Cal of energy are absorbed from the sheep rumen every 21+ hours. It is possible at this time to examine how the alfalfa concentrate, aspen and white cedar diets provide maintenance energy to deer. From Table 1h, a deer weighing 51.2 Kg requires about 1323 Cal in a 2h hour period. Barnett and Reid (1961:15) review several papers that state that volatile fatty acids supply a large proportion of maintenance energy to the ruminant. For illustrative purposes let us assume that 1000 Cal of energy may be furnished to a 51.2 Kg deer in 9. 2h hour period by volatile fatty acids synthesized /“\ 63 in the rumen. From Table 13 the rumen contents of a white-tailed deer may be about 6% of the body weight or about three Kg for a 51.2 Kg animal. The total amount of volatile fatty acids in the rumen of a deer can be extrapolated from Table 1. For the alfalfa concentrate diet the total acids present in 100 m1 of rumen material averaged 0.8112 g (950.38 mg+ 731.20 mg). Assuming that the strained rumen liquor, from which the aliquot for acid analysis was removed, was characteristic of the total rumen contents, there may have been 25.3 g of volatile fatty acids in the rumen (0.8h2 g/100 ml at 3000 m1 of rumen material). In like manner the total volatile fatty acid concentration in the deer rumen on the aSpen diet was 11.6 g and on the white cedar diet was 15.8 g. Such estimates of the amounts of total acid in the men are of the. same order of magnitude but are slightly lower than some published values for other ruminants. Barnett and Reid (1961:153) list the amounts of acid in the rumen and reticulum of the sheep grazing on pasture as varying between 26.8 and 91.1} g.. They also quote data of Elsden that the total volatile fatty acid level in the rumen of the ox was 286-371 g and that 65.2 g of volatile fatty acid was found in the rumen of the red deer, Esau}; elaphus. The red deer is consider- ably larger than the white-tailed deer, often weighing 150 Kg and presumably this animal also has a more capacious rumen. Assuming an average molar percentage of 65% acetic, 20% propionic and 15% butyric for the volatile fatty acids in the rumen, l‘. 6% and using the values of Brody (19h5z35) of 3.h9 Cal/g for acetic, h.96 for pr0pionic and 5.95 for butyric acid, it can be calculated that an average gram.of rumen VFA contains about h.15 Cal of energy. The total acid content in the rumen on the alfalfa concentrate diet would provide about 105 Cal, on the aSpen diet h8.l Cal and about 65.6 Cal on the white cedar diet. For the alfalfa concentrate diet to furnish 1000 Cal to the deer in a 2h hour period the volatile fatty acid level sampled in the rumen would have to be produced and absorbed about 9.52 times. This turnover rate would be half again as large on the white cedar diet, 15.2% times, and over twice as large on the aSpen diet, 20.79 times. Data from Stewart gtflgl. (1958) Show that on 1h occasions an average of 795 g of volatile fatty acid was present in the rumen of a steer and the total acid production averaged 2927 g for four diets in a 2h hour period. Thus the level of volatile fatty acids in the rumen was produced and absorbed about four times daily. For one control fermentation on the alfalfa diet (Table 1) 308 mg of volatile fatty acid were produced per 100 m1 of rumen liquor in a 3 hour fermentation. Extrapolating to 2h hours for a rumen with three liters of contents suggests a total.volatile fatty acid production of about 75 g which would furnish approximately 300 Cal to the deer. Thus from these data a 2h hour production of volatile fatty acid might be three times the concentration present within the 65 rumen. However, this rate of volatile fatty acid production does not substantiate the prOposed rapid fermentation rate within the deer rumen. Possibly the amount of volatile fatty acid pro- duced by the 3 hour i_n. .v_i_t£<_)_ fermentation (Table 1) does not reflect the true rate of acid formation within the rumen of the deer. It does seem likely, however, that the estimate that volatile fatty acids might furnish 1000 Cal a day to the deer is far too generous. Stewart 53 _a_l_. (1958) cite that only 37-h6% of the maintenance energy requirement of the goat is furnished by the rumen volatile fatty acids. It seems probable that such a level might more realistically approximate the contribution of rumen volatile fatty acids to the daily maintenance energy of the white-tailed deer. Though these data are extrapolated, perhaps even beyond merit, they illustrate the basic relationship between fermentation rates as measured by _i_r_1_ £31222. fermentations and the furnishing of maintenance energy to the white-tailed deer. L—ates _<_>_f_ Turnover p_i_’ R_u_m§_n_ Contents _ig the D_£e_r_ Hungate _e_t_ 9.2:. (1959) have argued that as small ruminants have greater basal metabolic rates per unit of body weight than do larger animals their total fermentation products per unit of body weight must also be greater. One manner in which an increase in total fermentation products could result is through a retention of food within the rumen thus allowing a more complete digestion. Pre- 66 sumably a longer retention of food stuffs within the rumen would necessitate a relatively large rumen in comparison with body weight. However, from Table 13, the rumen volume-body weight ratio of the deer is considerably less than that of the cow. Presumably an increased retention of food within the rumen is not an adequate eacplanation of how the deer obtains its necessary energy. It is interesting to note that the figures in Table 13 suggest a relatively larger rumen volume-body weight relationship in the sheep although the measurements for Sheep are much too frag- mentary to support any further discussion of the point. The high energ requirements of the white-tailed deer which are fulfilled by fermentation products from a rumen of relatively small size necessitate a high turnover rate of readily fermented foods within the rumen. Hungate g}; 11;. (1959) found that the Sunni (Nesotragus sp.), the dwarf antelope of Africa, generally had a large food consumption, a diet consisting of readily fer- mented foods and a high rate of fermentation within the rumen. Although inadequately described for the Great Lakes region the diet of the white-tailed deer probably normally consists of easily fermented foodstuffs -- succulent plant growth and mast in season, and includes certain preferred high-energ; high-protein conifers during winter. In addition the white-tailed deer generally has a slightly higher dry matter content within the rumen than does 67 the cow and produces slightly more fermentation products per 100 ml of rumen material. The turnover rates of contents within the rumen can be estimated by two techniques. The passage of materials refractive to microbial attack can be observed (Belch, 1950) or the weight of total dry matter within the rumen can be divided by the weight of the daily dry matter intake (Thomas gt 9.1., 1961). Generally these types of measurements have not yet been undertaken for the white-tailed deer although some indication of food turnover rates within the rumen can be obtained by the analysis of feeding experi- ments . Feeding Trials, Food Intake and Fermentation Rates From 1936-l9h1 the Michigan Department of Conservation carried on an extensive deer feeding study at Casino. The studies analyzed below consisted of feeding groups of adult deer different browse species or different combinations of browse Species during the winter season (Davenport, 1939 and undated). The food intake was measured and is expressed below as pounds (1b) of dry matter (m4) intake per hundredweight (cwt) per day. The change in condition of the deer during the feeding trials is expressed as per cent change of the original body weight. As the feeding trials were conducted for varying periods of time, the change in body weight is projected to 90 days. Ninety days is a convenient denominator as it represents the length of the average yarding season in the deep snow belt of the Cusino area. 68 Figure 1 lists the dry weight intake per cwt per day of ten common browse Species and alfalfa, clover and timothy hay. 0n the abcissa is recorded the per cent weight change incurred on each diet by the test animals. As might be expected there is a positive correlation between dry matter food intake and weight loss and the regression equation predicts a 1.87 lb/cwt/day dry matter intake for maintenance. The slope of the regression line in Figure 1, which is significantly different from zero at the 5% level of probability, signifies that the condition of an animal on a parti- cular diet is related to the dry matter consumption of that diet. Dry matter intake on the different diets was not dependent on palata- bility, that is the relative selectivity for a particular browse Species when “this food item was offered with other foods. The dry matter intake of a browse species was not correlated with the gross calories present (as determined from proximal analyses by Crampton, 1956:56), the crude protein, crude fiber, or nitrogen-free extract levels of proximal analyses nor with the total carbohydrates present in the browse species. All proximal analyses are expressed on a dry weight basis and all statistical tests were conducted at the 5% level of probability. Generally there is a direct relationship between dry matter intake and retention time of ingested food within the rumen. For example, Thomas _e_t_ _a_l_. (1961) found that when heifers were fed at the rate of 2.0 lb/cwt/day the retention time of food within the rumen 69 ‘was less than one day, but when food intake was less than 0.5 lb/cwt/day the rumen retention time was more than two days. It can be surmised from.Figure 1 that the retention time within the rumen for white cedar, for example, is considerably less than that for trembling aspen. This difference exists despite the fact that proximal analyses of these two browse Species (as listed by Davenport-— undated) are nearly identical. .A serious prOblem.in the feeding trials summarized in Figure 1 was the apparent unwillingness of test animals to eat a sufficient quantity of food to maintain their condition throughout the test period. 'Hhen combinations of different browse species or when combinations of browse Species with grain or meal supplements were fed, the dry weight food intake generally increased as can be seen from Figure 2. Under these feeding regimes increased dry matter intake is not directly correlated with weight change. Throughout these feeding trials diets containing white cedar generally gave superior performances and this browse, which is readily selected'by deer, is fairly readily fermented in 3g; zi§32_studies and has a.high total digestible nutrient value of 71.2 (determined by the method of Crampton, 1956:57, from data of Davenport, undated). ‘When white cedar was supplemented.by basal rations of barley, rye or oats (each with relatively high crude protein and total digestible nutrient values, Crampton, 1956:22h) H . . a. . y . . , . o c . r a F q . . . . ., .r n. . c I a. . 4 I ’0‘ c n . _ . . x t . I a J a i I a \ I i ' . \ — . a . . OK A . x. v . \t. w v .. k , I.‘ .. 1 t, u . . r w , 1 o , . e . . i . p r . i a c , _ , . . r \. . 0 . ,. .. a . . . . Ox ‘ . u u t u . 4 I . u .\ a. . . . . 1 n . . , — A i. \ x . . s t i o . 1 . . a. . ,1 , a _ _ . .. . . . .. . . a . . u . r v . a a . i l t, . _ / L _ . ) . . . , .> v‘ a .. . . v 1 . r , k 0 w w , , . . c v a A . u n H \ , . v u A '\ s . , y _ , , . l . A w r L K c h v I u ‘ , a , . _ w m . . . v 1 a \i . . , . V a 9x .. a. . t r . . F p ”I . \ e - . t . O\ a. . c . . . ‘ . v . . n . Ox 0 ., _ .. V . v w u . . . . c . A \ O p _ . t x i . J r . — .J . 1 . . . a . . r . . v. x a . 70 actual weight gains were recorded during the hibernal stress period. It is interesting to note in Figure 2 that the addition of white cedar to diet "X" increased dry matter consumption by about 0.9 lb and decreased weight loss by about h5%. High protein cottonseed meal supplement to diet "X” increased dry matter consumption'by about 0.1+ lb and decreased weight loss by 50%. The addition of cottonseed meal to the alfalfa hay diet increased.dry matter consumption.by about oneehalf pound and decreased weight loss by 15-20%. Cottonseed meal supplement, when added to clover'hay, increased dry matter con- sumption by 0.3 lb although not noticeably affecting weight loss. The addition of corn to timothy hay increased dry matter consumption by 0.3 lb and this high energy carbohydrate decreased weight loss by about 25%. These data demonstrate that foods of high crude protein levels and high total digestible nutrient values are consumed at relatively high levels of dry matter intake. These readily fer- mented foods provide sufficiently high levels of volatile fatty acids and other products of fermentation, on a daily basis, to give adequate energy for maintenance. Important aSpects of the overall physiology of deer yet to be measured are the presumed high rates of turnover of rumen contents, the absorption of volatile fatty acids through the rumen wall, and the extent of synthesis and utilization of microbial tissue by deer. Table 1h. Basal Metabolism of Deer Compared to that of Goats, Sheep and Cattlel Cow Goat and fidoelp, Sheep Deer Steer weight (kg) 36.0. 15.0 51.2 500 Heat produced per 2h hrs (Cal) as measured 800 1,160 1,323 6,200 Per kg 22.2 25.8 26.1 12.h Per square m.body surface 73k 917 937 1,09h ‘WO’73 37.8 h6.5 h8.5 h2.9 l . Taken from Silver gt_gl. 1959. Basal.metabolism of white-tailed deer-- a pilot study. J. Wildl. 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Lfi.\ . e .- t’g‘h's ' -j’ . w 1 o>eoemod ,- u .. --“l-.‘~ua-- .o-m-‘dl AHV. uxwflwB >003 cfl momcmno ucoswomnsm pom mxmucfl HmuumE >u© com: moumuucwocoo 0cm muwflt coflumcflneoo Mo muummwm .N mmDon o.H 1 .lm.H _ i .go.m v. "Awoaumm+wv LmON smumo+ya. 1 w Asossmm+mvg i. 13 W a u M M! m 1m.m . u ’ Am>m+Nv. . ioofi Aeq 18a 1M3 iea exenul pooa subtem Ala 'sqq 71+ EFFECT OF WHITE CEDAR ON CARBOHYDRATE DIGESTION The following data establish an intriguing generaliza- tion -- namely that the steer and deer utilized white cedar differently. This has been suggested above in the study of the total production of gases and volatile fatty acids of fermentation, although these data have been partially masked by the expression of fermentation products on a per unit of solid per hour basis. The sharp reversal of the general trend of in E239 cellulose digestion with rumen liquor from animals fed white cedar is also indicative of an intersPecific difference present. For this study the rate of disappearance of soluble carbo- hydrates from _in m fermentations was measured as described in the experimental techniques section. Control fementations consisted of three parts rumen liquor and one part 0.1 M phosphate buffer. In addition, the presence of white cedar, glucose and diethyl ether extracts of white cedar was programmed as listed in Table 15. In Figure 3 the logarithmic values of the carbohydrate determinations are plotted .on an arithmetric scale against hours of fermentation. Half life, the time required for one-half of the soluble carbohydrate originally present in a sample to disappear, is a useful discussion point for these fermentations. The half—life values are estimated by interpolation and are noted by asterisks in Figure 3 .1 1‘ 75 .Hfim is 90 mm adobe been: .88 Lim 8a to 90 mm 38 SE: .83 m 0? To 93 ~38 32: soon :A om m6 9mm 938 BE: noon 4A mm 8H 38 33: soon :83 mo.m 90 mm 938 33: noopm emma in to no mm 38 33: 33m :3.» SH 90 9% .268 32: sebum mA mm 03 “been 33: sooem emfm was to 90 mm :8 ..om.m mfl to 9mm. sou sh mm 90 9mm zoo in mm 03 3on. 39:52 Moan sofism .330 .3de dog god and 88m as No.0 33 coyotes deflect: 88% opgdbnoohmo .39 mo 0.“: maggophdo cowvspgnH mo soapamomaoo ”Emu Hum .33 oopdaflem ofismoeoez oogomndman gadgphou com: .3600 09.23 mo PooMMm vacuum 0.... muoapovsoahoh 0.3.; .mm .3 bands 76 and are listed as hours (') and minutes (") in Table 15. Rumen material from a cow, fed on alfalfa hay, required four hours for one-half of the soluble carbohydrates to disappear from the control fermentation. A.somewhat longer period of time was required for one-half of the carbohydrates to disappear when one-half per cent of white cedar was present in the incubation. Rumen liquor with one-half per cent glucose present had a half life period of 3'30" but a similar fermentation, differing only by the addition of one-half per cent of white cedar, required an additional 20 minutes. The addition of white cedar to these fermentations clearly lengthened the half life period but it is not possible to determine whether the white cedar was a difficult to ferment carbohydrate or somehow inhibited.microbia1 action. The white cedar fed steer produced a rumen liquor whose control fermentation Sported a half life greater than six hours. Rumen material fermented with one-half per cent glucose had a 7'h6" half life and the addition of one-half per cent of white cedar increased this half life period by 97 minutes. ‘White cedar, washed with diethyl ether until the green color and aromatic odor were not perceivable, had essentially the same half life as did the untreated plant material. These half life durations recorded for the steer are very appreciable and indicate a‘very slow rate of fermentation and therefore a very slow turnover rate of rumen contents. Actually 77 compaction within the rumen of the steer was so great that less than four pounds of cedar sprays per day (a very low intake level for a 600-800 lb animal) could be force fed. The half life of the control fermentation of rumen material from a deer fed on white cedar was greater than.four hours. The greater amount of soluble carbohydrate present in the control fer- mentation of the deer compared to that in the steer reflects the greater per cent solids in deer rumen liquor. ‘When one-half per cent of white cedar was added to the control fermentation a similar half life occurred, Judging from.the similar lepes of the two curves in Figure 3. The addition of glucose to the controlled fermentation produced a half life of two hours, nearly one-fourth that recorded for the steer. The addition of one-half per cent white cedar to the glucose fermentation prolonged the half life by 67 minutes producing a value about one-third that of the steer. ‘For rumen material from the deer, as with that from the steer, the half life with the diethyl ether extracted.white cedar was not appreciably different from that of the untreated.plant material. Several items are of interest about these fermentations with deer rumen material. This rumen liquor is the same as that which.produced the slow cellulose digestion in Table 10, the wider carbon dioxidedmethane ratios and the decreased total gas and total volatile fatty acid productions of Tables 1 and h. The rates of 78 carbohydrate disappearance from deer rumen material recorded in Table 15 may therefore be rather conservative estimates. At the end of four hours there was no evident difference in the amount of unfermented carbohydrate present in the glucose, glucose and white cedar, or glucose and ether extracted white cedar fermentations of deer rumen material. Presumably the greater half life of the incubations containing white cedar indicate that the carbohydrates of these incubations were somewhat less readily fermented than were those containing only glucose. The ten hour incubations of steer rumen material had a soluble carbohydrate level in the glucose fermentation that was significantly less than that present in the white cedar or ether extracted white cedar incubations. The gently decreasing slope of carbohydrate presence apparently indicates that a "small" microbifl population fermented the glucose at a slow initial pace but that the rate of fermentation increased possibly as the microbial pOpu- lation itself increased. The slow linear slope of soluble carbo- hydrate disappearance in the presence of white cedar presumably indicated that some constituent of white cedar limited the microbial p0pu1ation or at least its fermentation ability to a constant low rate. Discussion of White Cedar Oils and In Vitro Fermentations Generally the rate of fermentation of glucose within the rumen is linked with the diet of the animal. Anniaon and Lewis 79 (1959:87) cite findings that glucose disappeared at a slow rate from the rumen of a sheep fed a poor quality hay but that glucose was readily fermented in the rumen of the same animal when the ‘ experiment was repeated some weeks after the food had been changed to one of high quality. This correlation in diet was attributed to the amount of readily fermented carbohydrate present in the diet, and the relative numbers of micro-organisms present to attack the carbohydrate. The significance of the present experiments with the deer and the steer are that the same plant material acts as a readily fermented carbohydrate for one animal and inhibits microbial fermentation by the second species so that it requires three to four times as long for the steer to utilize white cedar as it does deer. There is a small literature attesting to the fungicidal and bacteriocidal property of the volatile oils of white cedar. Maruzzella and Liguori (1958) evaluated the antifungal activity of the volatile oils from 92 different species of plants. Eighteen pathogenic and non-pathogenic organisms were grown on petri dishes and small filter paper discs were cut, saturated with the test oil and placed on the petri dishes. The presence and absence of zones of inhibition and the total extent of the inhibitory zones were noted. The sum of the zones of inhibition from the volatile oils of white cedar was 11+7 which rated white cedar 16th in activity. The nature of the activity was shown to be fungicidal although no tests were 80 conducted for terpenless oils and no investigations were conducted to determine the nature of the fungicidal action. Maruzzella and.Lichtenstein (1956) used.similar techniques to test the effects of 110 volatile oils on the growth of various pathogenic and non-pathogenic gramrpositive and gramrnegative bacteria. The volatile oils of white cedar ranked #2 in this arbitrary listing of antiébacterial activity but in this instance there were no attempts made to identify the effect of the oils as bactericidal or bacteriostatic. It is interesting to note in this study that different bacteria varied in their reaction to the oils of white cedar. It is not known what substances in white cedar are inhibitory to the rumen micro-organisms of the steer, but presumably they are contained in a fraction that is not completely extracted with washings of diethyl—ether. lMaruzzella and Liguori (1958) state that the mode of antifungal action of volatile oils is not known although quinones (found.in essential oils) seem to be highly inhibitory for'both malt amylase and catalase of some fungi. They further report that some volatile oils have been shown to affect the dehydrogenase activity of paramecia and helminths. Perhaps there is a volatile oil in white cedar that in some manner adversely affected an enzyme system.of the rumen micro-organisms in the steer but not those in the deer which are sufficiently different so that 81 0Q -.._.--._---....;i,-...__.__...J o a _ cofiumuswfiumm mo.musom 0H m m h m m o m N H o q A III. _, a wcw>om .7 J Houucoo xmm 300 * nlo.H + I *.>. I ’1!!! C: / L 038 a. 13.1... l.+./ It /I [1” ”lo, o 58 c ........ Hm I o - n -+/ I L +/. INN/IO + t L «WHHIlllllMflHHHHWIIJIIIIIIIIlllw/Wnoosao + mom 300 l kHVHw + umoou muwnz + omoosaw + ham 300 mcoflumucoEumm onufl> cw Houo>om Eoum moumup>£onumo mHQSHOm mo oocsuoommumwo no noumm .m mmDGHm /L n 1 m N H H F; H sierpfiqoqzea atqntos smerbozorw 601 motto cease + sum zoo . .34 + l .7 \O H {\ o H (D H m r-I O N .N N N 82 they are not adversely affected by this inhibitory action. 0f considerable philosophical interest is the implication that a wild Species of animal may become adapted to undomesticated forages so that in some land use programs they are better adapted to the environment than are domestic animals. DISCUSSION Predicting the Digestibility (_a_; Food Stuffs This brief section discusses other research with deer that can utilize conventional techniques employed in the study of domestic animals. Studies summarized in the literature survey suggested that the proximal analysis of food stuffs should be supplemented to adequately measure the values of forages. In an earlier chapter attempts to correlate dry matter intake with differ- ent proximal analyses were quite unsuccessful. Studies with cattle and sheep have shown that the digestibility of food stuffs can be correlated with their chemical composition. Barnett and Reid (1961:139) list regression equations for digestible organic matter with both the crude fiber level and the lignin content of forages. No such equations have as yet been formulated for deer because an insufficient number of digestive coefficients have been obtained. In the future prediction equations develOped from digestion coefficients may allow the evaluation of food to be made from the chemical composition of the plant material. A second estimation of a food stuff's value to deer may be determined from _i_n Egg fermentations. Barnett and Reid (1961:1h8) state that some in; vitro methods give total digestible 83 81+ nutrient values which are in good agreement with lg gigg.measure- ments. Concurrent _i_n_ m4}. v_it_r_o_ digestibility trials with grass hays have shown a significant relationship‘between the two techniques. Generally $3 31352 procedures have the advantage of allowing experi- mentation with many samples and boast highly replicable results. .A complication.with extensive ipintgg studies with deer involves the sampling of rumen material. Short (undated) has commented on the application of the rumen fistula in the white-tailed deer. The greatest difficulty with the rumen fistula involves handling the animal as the temperament of the most docile of deer is quite re- sistant to confinement, extensive handling and rumen probings. Many of the same sampling difficulties are encountered with the use of stomach tubes and this procedure has the additional disadvantage of only supplying a limited sample of rumen liquor. If the test animal can'be regarded as expendable then igggi§32_determinations can‘be easily undertaken by sacrificing the animal, excising the rumen and removing the contents. ‘With the sacrificed animal complete aut0psies can be undertaken to obtain additional physiological informa- tion. There is a considerable effort and expense in Obtaining rumen samples from deer for in; vit___r_9_ measurements but the quantity of information and the ease of programming of _i_n_ _v_i_t_r;o_ fermentations accentuates the value of this technique in routinely testing the nutritive quality of different forages. - —.wv- '— 85 Research and.Management In.many white-tailed deer habitats an important aspect of management is the regulation of deer numbers with the available energy. Generally information about available energy in the en- vironment is not too well understood in deer studies although the biologist now has certain rather definite ideas of the energy, protein and mineral requirements of deer. The next step is to Obtain for the biologist estimates of how the environment provides these requirements. The present study has shown that different food substances in the same season provide different amounts of fermentation products. It is also known that in the latitude of Michigan a plant species undergoes vast and complex changes in its chemical composition throughout the year. For example, the protein of the growing plant is concentrated at first in the primary aerial structure, then in the leaves and finally in the seed. The protein content of a plant, like the soluble carbohydrates in the plant tissue, diminishes with the advancing maturity of the plant. Often this maturity is directly associated with the period of dor- mancy -- in Michigan the winter stress period for deer. This prOblem of differing nutritional values of deer browse items throughout the year is worthy of further study and.the following brief paragraph is a prospectus for such research. p. . “ I I . K x . r “ ‘ ‘ ' l' ‘ A i.\. . r . 71 o . . ../ .— I . o A . ‘ I 86 Deer used in this proposed research program, which is a 12 month food.habits and nutrition study, are penned in a newly constructed enclosure of convenient size. .A portion of these deer is to be sacrificed each month. ‘When a deer which is feeding at ‘will in the enclosure is collected the rumen is excised and samples of the ingesta are examined. The browse species present and their per cent composition of the rumen contents is determined on a dry weight basis. Because the test deer are in a little utilized range plot the rumen contents are analyzed at monthly intervals with regard to the browse plants extant in the enclosure to deter- mine the preferential selection of browse items. Rmnen liquor from the sacrificed deer is incubated in several.ipgzitgg'fermentations to determine the fermentation products of 0 hour, control and of several substrate incubations. Different substrates utilized in these studies are important plant species in the enclosure which are dutifully prepared.for’study'by air drying and.milling. Coin- cident with the survey of prominent plant species in the enclosure is their collection and subsequent proximal analyses to determine essential chemical composition. Though laborious, lengthy and ex- pensive such a research program would demonstrate (1) major changes in food items selected.by deer throughout the year, (2) volatile fatty acid levels in the rumen at different seasons and (3) the inpzitro_production of volatile fatty acids on individual browse substrates and combinations of'browse substrates at different seasons. 87 The ip'gitgg_digestibility of a single browse substrate at different seasons could then be compared with seasonal changes in the chemical composition of this browse species. This study could also Observe the interesting relationship between preferred food species and their rate of fermentation within the rumen. Studies of how'browse species become metabolically avail- able to deer suggest two management schemes. One managerial approach concerns certain food Species that are preferred.by deer and produce comparatively high levels of fermentation products during the winter. Such browse species could be favored and.manipulated in the environ- ment to provide maximum.available energy to deer at this season. .A second management scheme involves individual food Species that are extremely abundant in the environment which could be manipulated with regard to their physiology. For example, Reid 92 _a_l_. (1959) point out that the time of harvest is of utmost importance in evaluating the usefulness of forage for domestic livestock. There is a phase in the growth of a forage species where the digestible dry matter, a very important determinant of forage intake and digestibility in ruminants, is highest. Browses undergo the same physiological changes as do forages and.presumably'browses also reach a peak digestible dry matter value prior to plant maturation. Theoretically where deer foods are in short supply and pulp cutting is undertaken to add available energy to the deer's environment, such cuttings should occur prior to plant growth maturation when the 88 digestible dry matter value is highest. Possibly to aid deer in times of short food supply aspen and other pulp should be cut in June or July and the withered leaves and branches left for the winter food shortage periods. Even the decline in digestible dry matter caused by six months weathering might leave the cut aSpen a more nutritious deer food than the woody twigs usually provided in winter. Such hypotheses about deer management have sufficient merit to Justify experimentation and it is hoped that the basic experiments and the subsequent discussion within this dissertation point out the usefulness of studying how food substances are made metabolically available to non-domestic animals. SUMMARY This dissertation reports a first study of rumen fermenta- tion in the Cervidae and compares certain aspects of deer nutrition with those of a domestic steer. White-tailed deer (Odocoileus virginianus) and a Holstein- Friesian steer were fed a pelleted alfalfa hay-corn concentrate, terminal portions of the reproductive growth of big-tooth aspen (Populus grandidentata) and leaf sprays of white cedar (Thgla occidentalis). Samples of rumen liquor of both animals on the three diets were analyzed in the laboratory to compare (1) the composition and concentration of volatile fatty acids in the rumen material and (2) to qualitatively and quantitatively differentiate the volatile fatty acids and gases of fermentation. For the deer there were 10.88-13.96 milli moles of volatile fatty acid present per 100 m1 of rumen liquor on the alfalfa diet, 5.78 milli moles of volatile fatty acid on the aSpen diet and 7.68- 8.21 milli moles of volatile fatty acid on the white cedar diet. The level of volatile fatty acids on the alfalfa diet was similar to that determined for the steer but the volatile fatty acid levels on the aSpen and white cedar diets were greater than comparable measurements 89 90 for the steer. The ip_!itgg_fermentations of deer rumen liquor produced volatile fatty acid concentrations which on the alfalfa diet were similar to those produced by steer rumen liquor but which on the aspen and white cedar diets were significantly greater than those produced by steer rumen liquor. Fermentations of deer rumen material produced concentra- tions of gases on the alfalfa diet that were similar to those pro- duced by steer rumen material but on the aSpen and white cedar diets deer rumen material produced significantly greater concentrations of gaseous products. In fermentations of deer rumen material the gases formed a greater percentage of the total fermentation products and these fermentation products had a consistently higher calculated oxidation-reduction value than did the products from fermentations of steer rumen liquor. These data suggest that a somewhat more rapid rate of fermentation occurred for _i_g 33.332 incubations of deer rumen material and that a greater synthesis of microbial tissue may have occurred in these incubations. Deer nlmen material consistently contained a higher percentage of solid material which may have accounted for some of the increased products of fermentation on the aspen and white cedar diets. The results of the in _v_i_t_r;9_ cellulose digestions of solka floc and aspen and white cedar fibers tend to support the hypothesis of a rapid rate of rumen fermentation by deer. For the deer the range 91 of cellulose digestion of all fibers was similar, about 6-28%. For the steer solka floc digestion on the alfalfa diet was higher, fiber digestion on the aspen diet was similar to, and fiber digestion on the white cedar diet was somewhat less than comparable measurements for deer. Appreciable fiber digestion in the rumen requires a long incubation period. However, the presumed rapid fermentation rate within the deer rumen, necessitating a rapid turnover rate of rumen contents may indicate that relatively low fiber digestion is normal. for deer. White-tailed deer have a rather high basal metabolic rate and possess a relatively small rumen containing only modest amounts of volatile fatty acids at any one time. Rates of absorption of volatile fatty acids from the rumen and total production of volatile fatty acids in a 21+ hour period have yet to be measured. It seems possible, however, that 21+ hour volatile fatty acid production in the rumen may account for up to one-half of the required daily main- tenance energy of deer. It is further suggested that the utilization of microbial. tissue may furnish a sizeable portion of the remaining maintenance energy requirement. It is demonstrated that the addition of high energ, easily fermented food stuffs to browse or forage species increases dry matter intake and favorably affects the physio- logical condition of the animal. It is suggested that food items should be evaluated on the ease of fermentation or the rapidity with \ 92 which they become available to deer as well as their chemical composition. The apparent discrepancies between survival of deer under natural conditions and the results of controlled feeding experiments may reflect the inadequacy of present knowledge of deer food habits as deer may select and utilize plant tissue which can be readily made available to them through rumen fermentation. 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