Intake, digestibility, methane and heat production in bison, wapiti and white-tailed deer

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1 Intake, digestibility, methane and heat production in bison, wapiti and white-tailed deer J. K. Galbraith 1, G. W. Mathison 1,3, R.J. Hudson 1, T.A. McAllister 2, and K.-J. Cheng 2 1 Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta Canada T6G 2P5; 2 Research Centre, Agriculture and Agri-Food Canada, P.O. Box 3000, Lethbridge, Alberta Canada T1J 4B1. Received 25 September 1997, accepted 20 August Galbraith, J. K., Mathison, G.W., Hudson, R.J., McAllister, T.A. and Cheng, K.-J Intake, digestibility, methane and heat production in bison, wapiti and white-tailed deer. Can. J. Anim. Sci. 78: A 3 2 factorial experiment was conducted in which the digestibility of alfalfa pellets and methane and heat productions were measured in bison, wapiti and white-tailed deer in February/March 1995 and in April/May Voluntary dry matter intake (DMI) while animals were individually fed averaged 70, 87 and 68 g kg 0.75 d 1, respectively (P = 0.05), and was generally higher in April/May than in February/March. Corresponding organic digestibilities were 52.9, 54.1 and 49.1% (P = 0.10). There was also a trend (P < 0.1) for fiber digestibilities to be lowest for deer. Methane production (L kg 1 DMI), was 30.1, 23.5, and 15.0 L kg -1 for bison, wapiti and deer, respectively (P = 0.01), with more (P < 0.01) methane being produced in February/March than in April/May (28 vs. 18 L kg 1 DMI). No differences in heat production (kj kg 0.75 ) or estimated energy requirements for maintenance could be detected between species, although animals numerically produced 40% more heat (881 vs. 632 kj kg 0.75, P = 0.13) in April/May when feed intakes were higher than in February/March. It was concluded that DMI of native ungulates is higher in spring than winter and that methane emissions per unit feed consumed were the highest with bison and the least with white-tailed deer. Key words: Bison, deer, wapiti, digestibility, methane, calorimetry Galbraith, J. K., Mathison, G.W., Hudson, R.J., McAllister, T.A. and Cheng, K.-J Ingéré alimentaire, digestibilité, production méthanière et calorique chez le bison, le wapiti (cerf rouge d Amérique) et le cerf de Virginie. Can. J. Anim. Sci. 78: Dans les périodes de février-mars et d avril-mai 1995, nous avons mesuré, par une expérience factorielle 3 2, la digestibilité des agglomérés de luzerne et la production de méthane et la thermogenèse chez le bison, le wapiti et le cerf de Virginie. L ingéré libre de matière sèche (IMS) des animaux nourris individuellement était, respectivement, de 70, 87 et 68 g kg 0,75 j 1 (P = 0,05) pour les trois espèces. Il était généralement plus abondant en avril-mai qu en février-mars. Les taux correspondants de digestibilité de la matière organique étaient de 52,9, 54,1 et 49,1 % (P = 0,10). La digestibilité des fibres était en général plus basse (P < 0,10) chez le cerf de Virginie. La production de méthane (L kg 1 IMS) était, respectivement, de 30,1, 23,5 et 15,0 pour le bison, le wapiti et le cerf de Virginie (P = 0,01) et elle était plus importante (P < 0,01) dans la période février-mars que dans les deux mois suivants, soit 28 contre 18. On ne relevait aucune différence entre les espèces pour ce qui est de la thermogenèse (kj kg 0,75 ) ou des besoins énergétiques d entretien calculés, mais les bêtes produisaient 40 % plus de chaleur (881 contre 632 kj kg 0,75, P = 0,13) en avril-mai, la prise alimentaire étant plus abondante qu en février-mars. Il appert donc que l ingéré de matière sèche des ongulés sauvages est plus important au printemps qu en hiver et que les émissions de méthane par unité fourragère consommée étaient au niveau le plus élevé chez le bison et au niveau le plus bas chez le cerf de Virginie. Mots clés: Bison, cerf de Virginie, cerf rouge d Amérique (wapiti), méthane, calorimétrie Bison (Bison bison), wapiti (Cervus elaphus), and whitetailed deer (Odocoileus virginianus) now are commonly found on game farms in Canada. Populations of wapiti and white-tailed deer on Canadian farms in the early 1990s have been estimated at and , respectively, by Friedel and Hudson (1994) whereas corresponding estimates by C. Huedepohl (personal communication, Alberta Agriculture, Food and Rural Development, Edmonton, AB) for 1995 are and Numbers of farmed bison are more difficult to determine since there is no mandatory registry as there is for white-tailed deer and wapiti. However, it was estimated that in 1996 there were about bison in Alberta, with Alberta s bison making up approximately 50% of the farmed population in Canada (C. Huedepohl, 3 To whom correspondence should be addressed. gary.mathison@ualberta.ca. 681 personal communication, Alberta Agriculture, Food and Rural Development, Edmonton, AB). According to Hofmann (1989), bison, wapiti and whitetailed deer can be classified as roughage/grass eaters, intermediate/mixed feeders, and browse/concentrate selectors, respectively, based on their predominant natural diet and differences in the digestive tract, which better equips each group to digest its type of diet. Concentrate selectors have the smallest relative stomach size, least subdivision, and the largest openings between the stomach compartments (Hofmann 1988). Despite clear morphological and physiological distinctions, Gordon and Illius (1994) suggest that Abbreviations: DE, digestible energy; DM, dry matter; DMI, dry matter intake; ER, energy retention; GE, gross energy; HP, heat production; ME, metabolizable energy; MEm, metabolizable energy requirements for maintenance

2 682 CANADIAN JOURNAL OF ANIMAL SCIENCE body size is a more important factor influencing feeding behavior and digestive physiology of ruminant species. For example, when comparing digesta mean retention time in eight browsers, seven intermediate, and eleven grazing African ruminants they determined that 99.6% of the variance was explained by a model with body mass and food type. Similarly, Robbins et al. (1995) argue that both flow rate of liquid from the rumen and fiber digestion are strongly related to body weight. Bison, wapiti and deer, whether because of digestive design or body size, are expected to differ substantially in their ability to digest forages as well as in methane production. One source of inefficiency of feed utilization in ruminant animals is the loss of feed gross energy (GE) as methane. Methane is the second largest contributor to the greenhouse effect and has been estimated to contribute 15 17% of the greenhouse effect (Intergovernmental Panel on Climate Change 1992). Its atmospheric concentration has increased from the estimated pre-industrial revolution level of 0.7 to 1.7 ppm in 1989 (Tyler 1991). Globally, ruminant animals have been estimated to produce about 80 Tg (1 Tg = g) of methane each year, which is about 16% of the total annual global emission of 515 Tg (Watson et al. 1992). The wild ruminant population in temperate regions of the world has been estimated by Crutzen et al. (1986) to produce 0.37 Tg yr 1 of methane. McAllister et al. (1996) estimated that native Canadian ruminants produce 0.15 Tg yr 1. However methane production has not been measured previously in bison or wapiti and only a few values are available for white-tailed deer. Similarly, information concerning the energetic efficiency of these three species is limited. The objectives of our research were to compare digestive efficiency, maintenance requirements and methane emissions from wild ruminants and to test the hypothesis that the proportion of feed energy lost as methane is greatest in bison, lowest in white-tailed deer, and intermediate in wapiti. MATERIALS AND METHODS A 3 2 factorial experiment was conducted in which the digestibility of alfalfa pellets and methane and heat production (HP) were measured in bison, wapiti and white-tailed deer in February/March and in April/May All procedures were approved by, and carried out under the supervision of, the Faculty of Agriculture, Forestry and Home Economics Animal Policy and Welfare Committee and with advice from a veterinary consultant. Animals were cared for in accordance with the guidelines set out by the Canadian Council on Animal Care (1993). Study Area, Animals, Diet, and Group Feeding This study took place at the University of Alberta Ministik Wildlife Research Station in the Cooking Lake moraine approximately 50 km SE of Edmonton, Alberta, during the period from February to June in Five female bison (196 ± 24 kg), five female wapiti (151 ± 13 kg), and eight female white-tailed deer (34.9 ± 4.6 kg) were used for the study. All animals were approximately 1 yr old. The bison and wapiti were selected by weight from a larger herd. The bison were yearling calves brought to Ministik from Elk Island National Park east of Edmonton, Alberta. The wapiti herd at Ministik was established in The white-tailed deer were brought to Ministik in the spring of 1994 as orphaned fawns. Animals within each species were held in one pen prior to digestibility and calorimetry measurements in February/ March and in April/May. Voluntary feed intakes were recorded daily on a pen basis during the last 5 d during which animals were together in each of the two adjustment periods. Animals were fed sun-cured alfalfa pellets ad libitum throughout the experimental period. Digestibility Trials Animals received alfalfa pellets ad libitum for a minimum of 2 wk prior to each period but were only fed individually for 1 d prior to digestibility measurements, which were conducted at ad libitum intakes. Immediately before the digestibility period animals were weighed using a platform scale (Accurate Scale Industries Ltd. Model #DF1000, Vancouver, BC). The animals were penned individually to measure individual feed consumption 24 h before they were put in the collection crates ( m). The animals had been exposed to the collection crates at least once before the digestibility measurements were made, by holding them in the crates for a minimum of 3 h. The collection crates had a mesh floor to catch the feces and separate the material from the urine which was collected in a tub below the floor. Digestibility measurements were made over a 5 d period with the first week of measurements beginning on 6 March 1995 for the first period and on 1 May 1995 for the second period. The animals were randomly assigned to crates with at least one animal of each species put into the five crates each week. White-tailed deer were put into the crates in pairs since flow meters used in subsequent calorimetry measurements required higher air flow rates than were practical with a single deer. During each of the digestibility trials, orts were collected and feed given between 09:00 and 10:00 h. Animals had free access to water. Representative samples of feed, feces and urine were collected and transferred to a freezer at 20 C until further analysis. Hair in the feces was removed with a nail comb and the remainder was removed manually before laboratory analysis. Methane Production and Oxygen Consumption After the animals completed the digestibility trials they returned to the herd. Prior to respiration measurements they were penned individually for 24 h to record individual feed consumption. The calorimetry measurements began in the week following the digestibility trials in both periods. In period 1, the last animal finished calorimetry in the first week of April, and in the second period the last animal finished calorimetry in the first week of June. Outside air temperatures were obtained daily with a maximum-minimum thermometer during the respiration measurements. For methane and oxygen measurement, wapiti and bison were held in a chamber identical to the digestibility crates with the exception of a sealed solid floor while two deer

3 GALBRAITH ET AL. ENERGY PARTITIONING IN NATIVE RUMINANTS 683 were put into a smaller crate ( m), which was otherwise identical to the digestibility crates. The animals were left in the chambers for a total of 30 h and data were collected for the final 24 h. Air was continuously withdrawn from the chamber, and gas flow, temperature, pressure, and oxygen and methane concentration were monitored. Flow rates were adjusted to maintain an oxygen concentration in the chamber of 20%. The average flow rate over both periods for all species was 95 L min 1. The air was passed through Drierite (W.A. Hamond Drieritte Co. Ltd. Xenia, OH) to remove water before entering gas analyzers. The oxygen analyzer (Servomax model 540A) and the methane analyzer (Rosemount Analytical Model 880A, Rosemount, CA) were calibrated at the beginning of each 24 h measurement. Nitrogen gas was used to zero both analyzers, span gas (19.18% oxygen and % methane) was used to set the oxygen and methane analyzer s mid range, and atmospheric air (20.95% oxygen, McLean and Tobin 1987) was used to set the upper range on the oxygen analyzer. The data were collected once per second and averaged over 60 s by a Data Taker (Data logger DT100, Data Electronics, Australia), and then transferred to a computer using software designed to record the information (Datagrabber, University of Alberta). A known amount of nitrogen was released into the chambers to determine the accuracy of the system. A full bottle of nitrogen was weighed, placed into the chambers, and nitrogen was released over a known time period (approximately 10 min). The derived recovery factor was then used to adjust all measurements of gas flow. Calculations Heat production was determined using the formula M = 20.5V E Fo 2 (McLean and Tobin 1987), where M is the metabolic rate in kw (1 kw = 1 kj s 1 ), V E is the expired air flow rate at standard temperature and pressure for dry air in L s 1, and Fo 2 is the difference in O 2 concentrations by volume between inspired and expired air (F E F I ). Methane was converted to kilograms using the relationship 1 L CH 4 = g (McLean and Tobin 1987) and to energy equivalents by the relationship 1 L CH 4 = 40 kj (CRC 1978). Metabolizable energy (ME) requirements for maintenance (MEm) were estimated using the determined ME intake (MEI) and HP values and an estimation of fractional efficiency of utilization of ME for maintenance (km) and gain (kg) according to the following equation: MEm = MEI ER/k, where MEm = ME required for maintenance (kj kg 0.75 ), ER = energy retention (kj kg 0.75 ) and k = fractional efficiency of conversion of ME into net energy retained by the animal. The ER can be calculated as MEI HP thus the equation can be expressed as MEm = MEI (MEI HP)/k. The value assumed for k when ER was negative was 0.63 (National Research Council [NRC] 1984), whereas when ER was positive values used for k were either 0.38 or The 0.38 value was based upon information for cattle (NRC 1984) consuming a diet with an ME content of 8.4 MJ kg 1, which was close to that obtained in this study whereas the 0.67 value was derived with native ungulates (Jiang and Hudson 1992). Laboratory Analyses Feed and fecal samples were dried to a constant weight at 100 C and ground through a 1-mm mesh screen with a Thomas Wiley laboratory mill (model 4, Philadelphia, USA). Hydrochloric acid (1% by weight) was added to urine samples to minimize nitrogen losses and then the samples were freeze-dried (Virtis company 50-SRC freeze dryer, Gardiner NY) before analysis. Nitrogen was determined by the Kjeldahl procedure (Association of Official Analytical Chemists 1980) and GE by adiabatic bomb calorimetry (Leco automatic calorimeter AC 300, St. Joseph MI). Feed, feces and orts were analyzed for ash, neutral detergent fiber (NDF), acid detergent fiber (ADF), and lignin concentrations by procedures given by Van Soest et al. (1991). Sodium sulfite was not included in the NDF analysis, which could have resulted high in values if hair was present in the feces. Since hair was manually and carefully removed from the samples, we believe that any such contamination was relatively small. Statistical Analyses Data were analyzed using the GLM and LSMEANS procedures in SAS Institute, Inc. (1989) with comparisons for significant differences made by the probability of differences (PDIFF) option. The data were analyzed as a split plot design with animal nested within species as an error term for species. Differences between species, season (trial date), and their interaction were examined. The model was: Y ijkl = m + Sp i + A(Sp) j + S k + I l + e ijkl where Y is the dependent variable; m is the overall mean; Sp i is the species effect; A(Sp) j is animal nested within species effect; S k is the season (or time period) effect; I l is the interaction between season and species effect; and e ijkl is the residual error. RESULTS AND DISCUSSION Environmental Conditions, Feed, and Animal Handling Characteristics The mean outside temperature during February/March was +0.6 C and during April-May was +7.0 C. The suncured alfalfa pellets averaged 95.2% DM, 18.1 kj g 1 GE content, 13.9% protein, 59.2% NDF, 43.5% ADF, and 11.1% lignin on a DM basis. This composition is similar to that of mature alfalfa, which contains 12.9, 58 and 44%, protein, NDF, and ADF, respectively (NRC 1984). Feeding pellets rather than long hay would be expected to influence voluntary intake and to reduce fiber digestibility, methane production, and heat production in the animals. Alfalfa pellets were used, however, since it was necessary that all species receive the same diet, alfalfa is commonly fed to farmed ruminants, and pellets eliminated problems with sorting of feed (there was no difference in composition of the orts (values not shown) compared to that of the feed in our experiment). It is, however, recognized that this is not a natural diet, particularly for the white-tail deer, which are accustomed to eating browse-based diets containing

4 684 CANADIAN JOURNAL OF ANIMAL SCIENCE Table 1. Seasonal body weight and ad libitum DMI (g kg 0.75 ) of bison, wapiti and white-tailed deer DMI DMI DMI No. Liveweight group digestibility period calorimetry period Date and species animals (kg) period z Pre-trial Days 1 5 Pretrial Day 1 Species Bison ± ± a 69.7b Wapiti ± ± ab 87.1a Deer ± ± b 67.7b SE x Probability Time (1995) Feb. March ± ± b 53.7b 65.0b 72.4b April May ± ± a 95.9a 95.6a 101.2a SE Probability <0.01 <0.01 <0.01 <0.01 Species time Feb. March/Bison ± ± b ab 69.9 Feb. March/Wapiti ± ± c b 69.2 Feb. March/Deer 33.9 ± ± bc ab 78.0 April May/Bison ± ± a a 85.6 April May/Wapiti ± ± a a April May/Deer 34.8 ± ± b ab SE Probability < z Group intakes were measured during the last 5 d of each of the two adjustment periods. y Values following means are standard errors of animal weights and daily intake for animals kept in groups. There were eight deer, five bison, or five wapiti in each group. Measurements were taken over a 5-d period before digestibility trials in both time periods. x SE = standard error. a c Means in the same column and comparisons not followed by the same letter differ significantly (P < 0.05). tannins. This may be why the white-tailed deer required a longer time period than bison or wapiti to adjust to their feed and increase intake upon first exposure to the feed. Also, the deer chewed hair of other animals which may have been related to dietary effects. Although the deer were bottle-raised, they varied in their response to handling with some appearing quite relaxed and others quite nervous. Deer also had relatively low intake in group feeding situations and the low to negative nitrogen balances obtained during the digestibility trials. Pairing the deer was therefore not helpful in reducing variability. Data from one pair of deer during the digestibility trial and one bison during the calorimetry trial were not included in the analysis because of low DMI. Bison also became excited when handled and put into the crates, however, they settled more quickly than deer and seemed more content once they were in crates. Wapiti were by far the most even-tempered and gave the most consistent and results. They were appeared to be the most adaptable to the experimental conditions of the crates. Ad libitum Intakes Intakes and metabolic rates across species were scaled to metabolic weight (kg 0.75 ). Intakes over both measurement periods were 111, 86, and 46 g kg 0.75 for bison, wapiti, and deer, respectively, while the animals were in groups (Table 1). Differences between species could not be evaluated in this instance since animals were group-fed. Bison consumed 61% more alfalfa than deer (P = 0.02) during the pre-digestibility 24 h period and wapiti consumed more than either bison or deer (P < 0.05) during the 5-d digestibility trial. No DMI differences between species were detected during calorimetry measurements (Table 1). For all species intakes were higher (P < 0.01) during April/May than in February/March. There were interactions (P < 0.01) between species and date of measurement in both the predigestibility and pre-calorimetry DMI. Wapiti increased their intake in the April/May period more than either bison or deer; during the pre-digestibility measurements the DMI of wapiti was 3.7 times their intake in February/March. No data were found in the literature in which DMI of these species were compared when fed the same diet. The DMI of bison (111 g kg 0.75 while group feeding, and g kg 0.75 during individual feeding), were lower than values of 134 and 129 g kg 0.75 determined in summer/autumn and winter, respectively, for bison eating a 50/50 concentrate/ roughage diet (Stanton et al. 1994). In addition to dietary differences, another difference between the studies was that the animals used by Stanton et al. (1994) were bulls and the animals used in the present study were female. Although no comparative female vs. male intakes with bison are available, higher intakes have been measured in red deer stags over hinds (Suttie et al. 1987). The voluntary intakes of 86 g kg 0.75 by wapiti fed in groups and of g kg 0.75 when fed individually are higher than the February/March intake of 52 g kg 0.75 observed by Jiang and Hudson (1992). Although the animals in their study were all female and were fed a similar alfalfa pellet diet, they were, on average, larger animals than those in our experiment. Jiang and Hudson (1994) reported DMIs

5 GALBRAITH ET AL. ENERGY PARTITIONING IN NATIVE RUMINANTS 685 Table 2. Digestibility, nitrogen balance and urinary energy losses for bison, wapiti and white-tailed deer fed sun-cured alfalfa pellets z Digestibility (%) Nitrogen balance Urine Date and species n y DM x OM x GE x N x NDF x ADF x (g d 1 ) (kj d 1 ) Species Bison a 1064a Wapiti a 1124a Deer b 454b SEx Probability <0.01 <0.01 Time Feb. March b 701b April May a 1061a SE Probability <0.01 <0.01 Species time Feb. March/Bison b 939 Feb. March/Wapiti b 807 Feb. March/Deer c 358 April May/Bison a 1190 April May/Wapiti a April May/Deer c 550 SE Probability z The gross energy of the alfalfa pellets was 18.0 MJ kg 1. y No. of replications. x DM = dry matter, OM = organic matter, GE = gross energy, N = nitrogen, NDF = neutral detergent fiber, ADF = acid detergent fiber, DE = digestible energy, ME = metabolizable energy, SE = standard error. a c Means in the same column and comparisons not followed by the same letter differ significantly (P < 0.05). of 56, 62 and 103 g kg 0.75 d 1 when wapiti were fed barleyalfalfa pellets in winter, spring (March to May), and summer (1 June to 31 August), respectively. White-tailed deer had the lowest intake (46 g kg 0.75 ) during the group DMI measurement. This could partially be because the pair of deer that were excluded from the digestibility measurements due to low intakes were included in these measurements. The higher intake for the deer noted during the digestibility and calorimetry measurements (61 93 g kg 0.75 ) may be related to behavioral differences in response to housing and experimental conditions between the species since deer prefer a secluded area. No literature intakes of white-tailed deer fed alfalfa pellets were found, however Holter et al. (1977) fed male and female whitetailed deer fawns a cornmeal based pellet for 15 consecutive mo and measured DMI of 58 g kg 0.75 during February and March, which is 10 49% higher than the group/digestibility trial intakes for deer in this study (39 53 g kg 0.75 ). The DMI of 45 g kg 0.75 in deer fed a cornmeal-oat mill feed observed by Thompson et al. (1973) in January is closer to the intake in the present study. The intake for April/May in our study of 85 g kg 0.75 during the digestibility period is 44% higher than the 59 g kg 0.75 measured in May by Thompson et al. (1973), and 16% higher than the May DMI of 73 g kg 0.75 observed by Holter et al. (1977). The significant increase in voluntary intake in April/May has previously been seen in bison, wapiti and white-tailed deer. Bison fed varying proportions of concentrate (corn, soybean meal) and roughage (oat hay), showed a substantial reduction in feed intake during the winter (Stanton et al. 1994). Intake from June to November averaged 8.18 kg d 1 compared to the intake of 7.19 kg d 1 DM from November to March. A strong seasonal effect of voluntary intake has been observed in red deer hinds, with the highest intakes occurring in the summer months Suttie et al. (1987). Intakes have also been found to be highest in spring for white-tailed deer (Short et al. 1969). Thus, although long-term group feeding results were not obtained, voluntary intakes of all three species in this study were similar to literature values. Behavioral differences between species and an abnormal response of the deer to the pelleted alfalfa diet, however, makes it difficult to use these results to predict intake responses under natural conditions. Our data do, however, support previous findings that native ruminants have lower DMI in winter than in spring. Digestibility There were no detectable differences (P > 0.05) in digestibility of DM or nitrogen between species, however, there were trends (P < 0.10) for OM, NDF, and ADF digestibility to be higher in wapiti than in deer (Table 2). Time of measurement had no influence on digestibility, nor was there an interaction between time of measurement and animal species. No previous study has compared digestibility of a diet by these three species. Mould and Robbins (1982) discussed comparative digestive function in wapiti and deer and, in agreement with our results, concluded that elk digested fiber more completely than deer. They also noted that metabolic fecal losses were higher with wapiti than deer. Digestibility measurements were, however, not made for wapiti and deer with the same feeds or in the same trial in their experiment. In the case of brome hay, DM digestibility was 12% lower

6 686 CANADIAN JOURNAL OF ANIMAL SCIENCE in wapiti than deer even though the hay fed to the wapiti contained less ADF and NDF. We expected that bison, which are relatively large and roughage-grass eaters, would digest the fibrous parts of the feed most completely, especially in comparison to deer, which are smaller and browse feeders (Hofmann 1989). In a study comparing bison to yak and cattle, Richmond et al. (1976) found that bison had the highest NDF and ADF digestibilities when fed either grass or alfalfa hay. Similarly, Koch et al. (1995) noted that bison consistently digested more DM than cattle, even though the only significant effect was an 18% difference when alfalfa hay was fed. The form of feed may have affected our results since feed in the pelleted form passes through the digestive tract more quickly than feeds with long particle sizes (Mertens 1993). Hironaka et al. (1996) observed that pelleting reduced DM digestibility by 11% when chopped first-cut alfalfa was pelleted and the intake was 1.6 times maintenance. Hawley et al. (1981) has suggested that the relatively high apparent digestibilities obtained with bison in some trials may be because they have an enhanced capacity to recycle nitrogen to their rumen. However, since the alfalfa contained 13.9% crude protein in this experiment, ruminal availability of N should not have been limiting. There are no published values concerning the digestibility of alfalfa pellets by bison. Bison fed alfalfa hay have exhibited apparent DM digestibilities of 77.5% (Richmond et al.1976) and 70.1% (Koch et al. 1995). Wapiti hinds fed alfalfa pellets in our study had a DM digestibility of 51.2% during the overall trial which is very similar to that observed for suncured pelleted alfalfa in August (48%) by Hudson (unpublished observations) and of 46.5% in red deer fed lucerne hay in winter in New Zealand (Suttie et al. 1987). In the latter study, red deer had a 34% higher DM digestibility in summer than in winter. In contrast, digestibility of DM was numerically 8% lower in April/May than in February/March in our study. Similarly, Westra and Hudson (1981) found no temperature effect on digestive function in wapiti. Wapiti had NDF and ADF digestibilities of 44.0% and 41.3%, respectively, which are lower than previously published values of 50.6% and 49.8% for wapiti consuming alfalfa hay (Mould and Robbins 1982). No literature value for DM digestibility of alfalfa pellets in white-tailed deer was found; however, deer fed alfalfa hay had an apparent DM digestibility of 55.2% during a feeding trial in an undisclosed time of year (Robbins et al. 1975). This is higher than the average of 46.9% obtained in our trial. The NDF and ADF digestibilities for white-tailed deer were similar to values reported by Mould and Robbins (1982) for alfalfa hay. This perhaps suggests that whitetailed deer are not as sensitive to feed form as bison and wapiti. With expected higher passage rates through the digestive system in concentrate selectors (Hofmann 1988), pelleting would not be expected to have as great an effect on DM digestibility as with the other two species. Urinary Nitrogen and Energy Excretion Deer retained less (P < 0.01) nitrogen than either wapiti or bison (Table 2). More nitrogen was retained in April/May than in the February/March period. There was also a species by date interaction (P < 0.03) with the bison and wapiti both retaining more nitrogen in April/May, and deer exhibiting no difference between periods but having lower N retention than either bison or wapiti in both measurement periods. Bison had a nitrogen balance of 27.1 g d 1. Wapiti in our study had a retained 12 g N daily more than red deer in the study of Simpson et al. (1978). The overall mean of nitrogen retention of 0.3 g d 1 in white-tailed deer is lower than, but not far from, a previously published value of 1.5 g d 1 (Holter et al. 1979). The April/May N retention in this study (3.7 g d 1 ) was also close to the summer value found by Holter et al. (1979) of 5.0 g d 1. The animals in the study by Holter et al. (1979) were also fed a pelleted diet ad libitum. White-tailed deer excreted less (P < 0.01) urinary energy than bison or wapiti (Table 2), which is expected because of their lower intake. More (P < 0.01) urinary energy was excreted in April/May than in February/March. Methane Emissions EFFECT OF SPECIES ON METHANE PRODUCTION. Methane production (L kg 1 DMI) varied significantly by species with the following ranking: bison > wapiti > deer (Table 3). Bison lost the greatest percentage of their GE intake as methane, with an average of 6.6% being emitted over both seasons (Table 3). There are no reports on methane production of bison but the results of this study suggest that bison are similar to cattle, which were found to lose 5.9% of their ingested GE when fed pelleted alfalfa at a level of 97 g kg 0.75 d 1 (Hironaka et al. 1996). Averaged over both measurement periods, the percentage of GE lost as methane by wapiti was 5.2% which was lower (P < 0.05) than the bison but higher than deer. Sika deer (Cervus nippon), also classified as intermediate feeders (Hofmann 1988), lost 6.6% of their GE intake as methane when fed an unspecified diet (Zhonokuan et al. 1996). White-tailed deer, which have been classified as concentrate selectors (Hofmann 1989), had a lower (P < 0.05) methane production than either bison or wapiti. The amount of methane lost by deer expressed as a percentage of GE intake in the March/April, and May/June periods was 3.5 and 3.1% respectively (Table 3). These productions are similar to the range of 3.5% to 4.7% of GE intake measured by Holter et al. (1979) with white-tailed deer consuming a variety of diets. EFFECT OF SEASON ON METHANE PRODUCTION. Averaged over all animals, methane losses equivalent to 6.2% of GE intake in February/March and 3.9% in April/May, with the earlier value being 159% (P = <0.01) of the latter value. There was a species by month interaction (P = 0.06), with deer exhibiting little difference between the February/March and April/May value and the other two species showing a marked seasonal effect. Bison appeared to be particularly affected by month; production was 8.6% of GE intake in February/March as compared with 4.7% in April/May. It has been thought that methane production in ruminants is lowest in cold weather (Kennedy et al. 1978; Christopherson and Kennedy 1983) but recent evidence sug-

7 GALBRAITH ET AL. ENERGY PARTITIONING IN NATIVE RUMINANTS 687 Table 3. Methane production in bison, wapiti, and white-tailed deer L kg 1 DM L kg 1 digestible % of gross Date and species n z L d 1 intake y DM intake kj d 1 energy intake Species Bison 7 121a 30.1a 62.7a 4840a 6.6a Wapiti 10 87b 23.5b 45.4b 3480b 5.2b Deer 7 33c 15.0c 32.5b 1320c 3.3c SE y Probability <0.01 <0.01 <0.01 <0.01 <0.01 Time Feb. March a 55.8a 3320a 6.2a April May b 39.4b 3120b 3.9b SE Probability 0.57 <0.01 < <0.01 Species time Feb. March/Bison Feb. March/Wapiti Feb. March/Deer April May/Bison April May/Wapiti April May/Deer SE Probability z No. of replications. y DM = dry matter, SE = standard error. a cmeans in the same column not followed by the same letter differ significantly (P < 0.05). gests that methane production may actually increase in cattle and sheep with declining temperatures (von Keyserlingk and Mathison 1993; Dmytruk et al. 1995). However, we cannot separate the effects of month, temperature and intake on methane production from the current experiment. There only was a difference of 6 C in temperature between the February/March and April/May measurement periods and intakes were considerably higher in the April/May measurement period than in the February/March period (Table 1). Dmytruk et al. (1995) found that the proportion of GE lost as methane decreased with increased intakes. Lower feed intakes are expected to result in longer retention times for feed in rumen and thus in enhanced the activity of methanogenic bacteria in the rumen. Okine et al. (1989) observed that when passage rates through the digestive tract were increased by 63% methane production was reduced by 29% in cattle which were fed identical diets and in the same environment. Whether the differences in intake were enough to cause changes in methane production as a proportion of GE intake of 13 83% as observed in this experiment, however, remains for another study. ESTIMATES OF METHANE PRODUCED FROM CANADIAN GAME FARMS. From the above information it can be concluded that using 9% of GE lost as methane, as has been done in the past (Crutzen et al 1986) for the calculation of global contribution of methane release from wild ruminants, would overestimate production, particularly with wapiti and white-tailed deer since values in our study were 6.6, 5.2, and 3.3% for bison, wapiti, and white-tailed deer, respectively. With the estimated numbers of animals on game farms in 1995 in Canada of approximately bison, wapiti, and 7039 white-tailed deer (C. Hudepohl, personal communication, Alberta Agriculture, Food and Rural Development, Edmonton, AB); and using the calculated daily methane output per day from this study of 121, 87, and 32 L d 1 CH 4 for bison, wapiti, and white-tailed deer, respectively, the annual contribution of each species to global methane production can be calculated. This is a minimum estimate of the contribution of Canadian farmed native ruminants since the animals in our trials were sub adults and all females with average weights of 196, 151 kg, and 34 kg for bison, wapiti, and deer respectively (Table 1) and less methane is likely be produced when a pelleted diet is fed. Nevertheless the values from this study, are , , and Tg yr 1 of methane for bison wapiti, and white-tailed deer respectively. In comparison, McAllister et al. (1996) quoted figures of 0.15 and Tg yr 1 for total production from Canadian wild ruminants and cattle, respectively. Digestible and Metabolizable Energy Content of the Diet Neither digestible energy (DE) nor ME contents of the diet differed among animal species (Table 4). Similarly, these parameters were not influenced by date or a species by date interaction. The DE concentration of alfalfa pellets for bison and wapiti in this study (9.2 MJ kg 1 ) was equivalent to the average content for mature alfalfa hay reported for beef cattle NRC (1984) whereas the DE content of the pellets for deer was 91% of the NRC (1984) value. The ME content of the pelleted diet for these species ranged from % of ME content of mature alfalfa hay (NRC 1984). In this study, ratios of DE to ME were 0.82, 0.87, and 0.87 for bison, wapiti, and deer, respectively (P > 0.05; Table 4). This compared to the common value used for beef cattle of 0.82 (NRC 1996). The lower ratio of ME to DE in

8 688 CANADIAN JOURNAL OF ANIMAL SCIENCE Table 4. Dietary energy concentrations and energy balances for bison, wapiti, and white-tailed deer Dietary energy Energy partitioning y Calculated MEm x (MJ kg 1 ) (kj kg 0.75 d 1 ) (kj kg 0.75 d 1 ) Date and species n z DE x ME x ME:DE DEI x MEI x HP x ER x Cattle k x g Wapiti k x g Species Bison ab 583b Wapiti a 732a Deer b 561b SE x Probability Date Feb. March / b 621b 487b April May / a 866a 763a SE Probability <0.01 < Species time Feb. March/Bison Feb. March/Wapiti Feb. March/Deer April May/Bison April May/Wapiti April May/Deer SE Probability z No. of replications. y Energy partitioning during the 1-d calorimetry period. x Abbreviations DEI = digestible energy intake, MEI = metabolizable energy intake, HP = heat production, ER = energy retention, Kg = efficiency of ME use for gain, and SE = Standard error. a,bmeans in the same column not followed by the same letter differ significantly (P < 0.05) bison was attributable to the higher methane production during February/March (8.6% GE; Table 3). For deer, the ME:DE ratio of 0.88 observed in April/May was identical to that determined by Holter et al. (1977), and was also very close to the value of 0.87 found by Thompson et al. (1973) with deer. The animals in both of these studies were fed a corn-meal based diet. An effect of time of measurement (P = 0.02) on the ME:DE ratio was present, with ratios being higher in April/May than in February/March (0.83 vs. 0.88). Energy Intakes, Heat Production and Estimated Maintenance Requirements METABOLIZABLE ENERGY INTAKES. The ME intake of wapiti was 30% higher (P = 0.04) than that of deer during calorimetry trials and 25% higher (P = 0.04) than bison (Table 4). Similarly, ME intakes were 57% higher in April/May than in February/March. No significant species by date interaction for ME intake was apparent. The intake of ME averaged over both calorimetry measurement periods for bison from this study was 583 kj kg No values for ad libitum MEI for bison were found in the literature. The voluntary intakes of ME for wapiti were 546 and 917 kj kg 0.75 in February/March and April/May, respectively (Table 4). The March intake is very similar to an average voluntary MEI for winter of 550 kj kg 0.75 d 1 (Fennessy et al. 1981; Cool 1992; Jiang and Hudson 1992; Jiang and Hudson 1994). A seasonal effect on calculated MEI was also found in red deer (Cervus elaphus), with MEI of 500 kj kg 0.75 in summer and 400 kj kg 0.75 in winter (Suttie et al. 1987). This seasonality would be expected with the spring/summer period typically being a time of rapid growth for the animal. The voluntary ME intake obtained for white-tailed deer from this study in February/March was 438 kj kg 0.75, which is within the range of previously published voluntary intakes of 548 kj kg 0.75, kj kg 0.75, and 523 kj kg 0.75 (Ullrey et al. 1970; Thompson et al. 1973; Worden and Pekins 1995). The ME intake in April/May in the present study for white-tailed deer was 683 kj kg 0.75, which is numerically lower than the average summer ME intake found in the literature of 740 kj kg 0.75 from Thompson et al. (1973) and Holter et al. (1977). HEAT PRODUCTIONS AND ENERGY RETENTIONS. Variances were not homogenous for heat production, energy retention, or calculated NEm requirements, with deer exhibiting much greater variability than the other two species. Removal of deer from the analysis of variance reduced the variance by between 60 and 70% but did not result in detection of any significant differences between treatments. The greater variability in the deer data may have been because intakes in the pre-trial and calorimetry periods were reasonably similar for bison and wapiti but more variable for deer. Heat production measurements are affected by feeding level, temperature and stress, among other factors. The temperature during the experiment would have been above the lower critical temperatures of bison (< 30 C [Christopherson et al. 1979]) and wapiti ( 20 C [Parker et al. 1984]). Whitetailed deer have been found to have much higher lower critical temperatures in the winter of around 2 C (Mautz et al.1992). Since the mean environmental temperature was only 0.6 C during the first period, this may have resulted in an increased HP in some individuals at this time.

9 GALBRAITH ET AL. ENERGY PARTITIONING IN NATIVE RUMINANTS 689 Heat production might be expected to increase when animals are put in a respiration chamber, however this was not considered to be a major source of error in our experiment. All animals were well adjusted to the chambers, particularly by the second measurement period since a 5 d fecal and urine collection period preceded each respiration measurement. Calorimetry measurement periods of longer than 1 d, which would have aided adaptation to crates, were not possible because of animal welfare considerations. Heat production combined over both measurement periods were 651, 697, and 921 kj kg 0.75 d 1 for bison, wapiti, and deer, respectively (P > 0.05; Table 4). There was a seasonal effect (P = 0.02) when only bison and wapiti were considered, with HP being 33% higher in April/May, however no difference due to season was detected when deer were included in the analysis. No species by date interaction was detected. No differences could be detected in ER between bison, wapiti, deer or season, or their interactions (Table 4). However, in general, more energy was retained (or less lost) when ME intakes were higher in the April/May period. The negative energy balances which were observed for bison, coupled with the positive nitrogen balances (Table 2) suggests that this species may have been losing body fat during the calorimetry trials. ESTIMATED MAINTENANCE REQUIREMENTS. By definition, the ME requirement for maintenance (MEm) is the ME intake at which MEI = HP. If MEI and HP are not exactly equal, estimated efficiencies of ME use for maintenance and gain can be used in the calculation of MEm. There may be a difference in relative efficiencies between ME use for maintenance and gain between cattle and wapiti. According to the Agricultural Research Council (1980) estimates, a pelleted diet containing 11.2 MJ ME kg 1 DM and with a metabolizability of 60% fed to cattle would be expected to have efficiencies of ME use of 71 and 48% for maintenance and gain, respectively. Jiang and Hudson (1992) obtained a considerably higher value for efficiency of ME use for gain for wapiti of 67%. Therefore MEm estimates in Table 4 have been calculated using an efficiency of 71% for maintenance and either 48 or 67% for gain. There were no differences (P > 0.05) between bison, wapiti, or deer, or with season of trial, nor were there interactions with species and time of measurement on MEm calculated using either cattle or wapiti efficiencies (Table 4). In February/March only one bison, no wapiti, and one pair of deer were in positive energy balance. In the second period (April/May 1995), one of three bison, four of five wapiti, and two of four pair of white-tailed deer had MEI > HP; potential errors in estimates would be less when animals were below maintenance since efficiencies of ME use are higher. The average MEm estimates for bison in February/March and April/May were and kj kg 0.75 d 1, respectively. No previously published values for ME requirement for maintenance in bison was found. Using an efficiency of ME use for maintenance of 71%, the comparative requirement for a female 400 kg yearling beef heifer of normal breeding at 5 C is 514 kj kg 0.75 (NRC 1996), which is 15 33% lower than the values for bison. Although this difference indicates a higher maintenance requirement for bison, some of the difference could be due to differences in temperament of cattle and bison and their reaction to being in a respiration chamber. In addition, cattle breed is known to affect maintenance requirements, with dairy types having a 20% higher maintenance requirements than beef types (NRC 1996). Thus the MEm requirements of bison are within the range observed for cattle, although they appear to be influenced more by season. This study showed an average calculated MEm value for maintenance for wapiti of 620, and kj kg 0.75 d 1 in February/March and April/May respectively. Again, these estimates are 20 and 12 45% higher than the cattle estimate given above. The February/March MEm requirement for wapiti of 620 kj kg 0.75 d is also somewhat higher than both the winter value determined by Jiang and Hudson (1994) of 493 kj kg 0.75 d 1 and the value determined by both Fennessy et al. (1981), and Cool (1992) of 570 kj kg 0.75 d 1. The animals in the study by Fennessy et al. (1981) were stags and the animals in the study by Cool (1992) were calves, which are expected to have an higher MEm requirement. The calculated MEm for wapiti in spring (April/May) of 748 kj kg 0.75 d was similar to the value of 728 kj kg 0.75 d 1 published by Jiang and Hudson (1994), but lower than values published for wapiti in the summer of 936 kj kg 0.75 d 1, and 878 kj kg 0.75 d 1 (Jiang and Hudson 1992; Wairimu et al. 1992, respectively). An explanation for the difference in the MEm found in the present study and those of Jiang and Hudson (1992) is that their values include the energy cost of free ranging on a pasture. It has been estimated that ecological maintenance (energy for energy equilibrium of free existence) is about 1.6 times physiological maintenance (Jiang and Hudson 1992). The MEm of white-tailed deer were estimated as and kj kg 0.75 d 1 in February/March and April/May, respectively. Standard errors of these measurements were high (466 and 410 kj kg 0.75 d in February/March and April/May, respectively) and therefore the mean values should not be considered to be precise. Ullrey et al. (1970), Thompson et al. (1973), and Worden and Pekins (1995) obtained winter MEm estimates of 548, 523, and kj kg 0.75, d 1, respectively. The MEm for white-tailed deer in summer has been estimated at 678 and 803 kj kg 0.75 d 1 by Holter et al. (1977) and Thompson et al. (1973), respectively. Conclusions and Implications The DMI of animals in the present study was similar to previously published values and support findings that bison, wapiti, and white-tailed deer have greater DMI in spring than in winter. Individual voluntary ME intakes averaged over both periods were 583 and 732, and 561 kj kg 0.75 for bison, wapiti, and white-tailed deer, respectively. Surprisingly the three species did not differ in their ability to digest DM, organic matter, energy, nitrogen, NDF, or ADF of the pelleted alfalfa diet. Bison lost the greatest proportion of their GE intake as methane followed by wapiti and white-