Rioja-Lang, F. C., Galbraith, J. K., McCorkell, R. B. et al. 2019. Review of priority welfare issues of commercially raised bison in North America. Applied Animal Behaviour Science 210, 1-8.
A review of the scientific literature on bison was carried out as part of the National Farm Animal Care Council´s (NFACC) process of updating Canada’s current Code of Practice for the Care and Handling of Farmed Bison. Four priority welfare issues were identified: the effect of seasonality on the nutritional requirements of bison; bison behaviour; euthanasia on-farm; and pain. Bison reduce their feed intake and activity during winter, sparing energy reserves during periods of cold temperatures and food scarcity. To promote consistent carcass quality in this highly seasonal animal, producers commonly feed bison high grain diets. It has been suggested that feeding bison high concentrate finishing diets, greater than 80%, over a significant period of time, is likely to cause ruminal acidosis. Research is required into strategies that could help producers manage the effects of seasonality and to make it work to their advantage. When bison are unable to compensate for nutritional seasonality in summer it can lead to reduced herd fertility from poor nutrition and reduced body condition. Regarding behaviour, the handling of bison differs from traditional cattle handling techniques, as they do not move the same way through handling facilities. Injuries and death during handling are more likely to occur if bison are handled incorrectly. They are more excitable than cattle, which have been bred for calm temperaments. Bison have a very intact social structure that has definite spacing requirements. The flight zone of bison tends to be much greater than that of cattle, and bison can be moved most effectively if the handlers work on the edge of it. Bison that become severely stressed during handling can suffer from a recognized condition known as capture myopathy. Handling facilities should restrict bison’s vision and minimize loud noises. Bison should never be left in isolation as solitary bison display high levels of agitation. In the event of euthanizing bison on-farm, specific information regarding the gauge, calibre of firearm, and bullet selection is lacking. However, the combination of firearm and ammunition selected must achieve a muzzle energy of at least 1000 ft-lb (1356 J) for animals larger than 400lbs (181 kg). Understanding the correct landmarks for euthanizing bison are especially important as they are anatomically different from cattle. Due to the physical thickness of a bison skull, higher calibre firearms or heavier gauge shotguns are required than those used for other species. Bison producers in Canada rarely, castrate or brand animals, and they are seldom dehorned. There is currently a lack of peer reviewed research regarding the effect of painful procedures in bison, however, there is little reason to suspect their physiological responses to pain are different to cattle. Both freeze branding and hot-iron branding cause pain and distress in bison, however in cattle, freeze branding causes less acute pain at the time of the procedure which would likely be similar to bison.