Three thousand three hundred twenty-nine (3329) bison from 16 Peace Country bison herds were weighed between November 1992 and October 1994 to determine body weight, gain and to measure herd productivity. A survey of management practices was used to develop three producer profiles: 1) small herds (∼30 head), 130 ha and significant off-farm responsibilities, 2) full-time – 110 breeding females on 1040 ha, and 3) large ranches – 450 breeding females on 2080 ha. Calf winter weight was significantly (P < 0.0001) affected by HERD, YEAR and GENDER with males (196 ± 2.0 kg) significantly heavier (P < 0.0001) than females (180 ± 2.6 kg). Calves of both genders were heavier in 1993 than in 1992. Producers reporting herd health problems also had calves with lower (P < 0.0001) winter weights than herds reporting no health problems (175 ± 1.2 kg vs. 198 ± 1.2 kg). Seasonal ADG ranged from −0.08 kg d−1 to 0.56 kg d−1. A significant relationship existed between winter ADG and subsequent summer ADG (Y = −0.50X + 0.71; P < 0.0001). The results from this study of Peace Country bison are sufficient to serve as industry benchmarks to which producers can compare their herds. Key words: Bison, management, weight, gain, productivity

parameters of yearling bison were estimated using the bite-count and single marker methods (field trials) during each solstice and equinox between June 1994 and December 1995. To calibrate the marker method and to provide a controlled estimate of seasonal requirements, balance trials were conducted in metabolism crates during winter solstice 1994 and summer solstice 1995 (pen trials). In pen trials, actual metabolizable energy (ME) intake was lower (P < 0.01) during winter (528 ± 51 kJ W -0.75 d -1 ) than in summer (917 ± 69 kJ W -0.75 d -1 ). Similarly, in field trials, estimated ME intakes were lower for both bite count (P < 0.01) and marker methods (P < 0. (June 1995). Seasonal variation (P < 0.05) in total digesta turnover time (46.4 ± 1.4 h, December 1994; 24.9 ± 2.7 h, June 1995) was related more consistently to seasonal differences in transit time (18.2 ± 1.2 h, 4.0 ± 0.8 h, respectively) than differences in reticulo-rumen and lower tract turnover time. Bison exhibited strong seasonal differences in energetic parameters like other northern wild ruminants. . Dans ces derniers, l'ingéré réel d'énergie métabolisable, EM, était moins abondant (P < 0,01) durant l'hiver, soit 528 ± 51 kJ PC -0,75 qu'en été : 917 ± 69 kJ PC -0,75 j -1 . De même, dans les essais en grands parcours, l'ingéré de EM était plus bas durant l'hiver que durant l'été, qu'il soit calculé d'après le nombre de coups de dent (P < 0,01) ou par la méthode au marqueur (P < 0,05), soit respectivement 819 ± 375, et 146 ± 105 kJ PC -0,75 j -1 contre 1977 ± 186, 408 ± 53 kJ PC -0,75 j -1 . Les besoins énergétiques calculés d'après l'ingéré réel (essais en parquets) se chiffraient par 532 ± 178 kJ PC -0,75 j -1 en hiver et par 956 ± 107 kJ PC -0,75 j -1 en été. Dans les essais en grand parcours, les besoins calculés en EM (méthode du marqueur) se situaient entre 146 ± 22 kJ PC -0,75 j -1 en hiver 1994 à 478 ± 45 kJ PC -0,75 j -1 en été 1995. Les variations saisonnières (P < 0,05) du temps total de renouvellement du digesta : 46,4 ± 1,4 h en décembre 1994 à 24,9 ( 2,7 h en juin 1995 étaient reliées plus régulièrement à celles du temps de transit gastro-intestinal, respectivement 18,2 ± 1,2 h, 4,0 ± 0,8 h, que celles du temps de rétention dans le réticulo-rumen et celles du rythme de renouvellement dans la partie inférieure du tractus digestif. Ces variations saisonnières des paramètres énergétiques sont également propres à d'autres ruminants sauvages des régions septentrionales. Mots clés:Bison, caractère saisonnier, besoin en énergie métabolisable, ingéré, paramètres d'excrétion, pâturage Plains bison (Bison bison L.) have been farmed since the late 1800s when the species was rescued from extinction (Hornaday 1890;Roe 1970;Dary 1974). Although now managed similar to domestic livestock, they still retain many of the characteristics attributed to wild ruminants. Christopherson et al. (1978) reported seasonal variation in energy expenditures for penned bison (higher spring than winter values) -variation similar to other northern wild ruminants. No stu...

Activity budgets and foraging behavior of yearling bison (Bison bison L.) on pasture were studied during quarterly trials between June 1994 and December 1995. Daily activity patterns were polyphasic with alternating bouts of foraging and resting activity. During winter, bison displayed 2 main daytime foraging bouts and significant nighttime foraging. During summer, phasic activity was poorly expressed due to the increased number of cycles. Total foraging time declined from summer to winter (763 ± 62 to 470 ± 32 min day -1 ) while bedding bout length increased (121 ± 13 to 276 ± 26 min day -1 ). Bison selected forage higher in crude protein (12.9 ± 0.8 vs 10.0 ± 0.8%), higher in predicted digestible energy (2.70 ± 0.09 vs 2.17 ± 0.09 Mcal kg -1 ), lower in acid detergent fiber (31.9 ± 0.9 vs 38.8 ± 0.9%), and lower in lignin (4.8 ± 0.3 vs 6.8 ± 0.3%, respectively) than forage available within grazed patches.

The performance of bison finished on grain and forage was evaluated in summer and winter. In the first experiment, 58 bison bulls were finished for slaughter (90 day period beginning in late October 1993 and 1994). Half of the bulls fed with a feed-weigh station were compared to bulls fed with industry standard self-feeders. No significant differences (P>0.05) were found in average daily gain between the two feed delivery methods. The feed-weigh station then was used to assess seasonal effects on average daily gain of 156 bison bulls. After correcting for initial body weight, average daily gain was higher in summer (1.1 kg/d~'±0.004) than in winter (0.7 kg d'±0.005). This was associated with higher average daily feed consumption in summer (14.3 kg d"'±1.15) than in winter (10.6 kg d"'±1.15). Although not as striking as in northern cervids, seasonal energetic cycles of bison are a significant consideration in commercial management.