SICKNESS, MORTALITY AND THE BULLER STEER SYNDROME IN A WESTERN CANADIAN FEEDLOT

Objective To determine if an association existed between sickness, mor tality and bullers in a western Canadian feedlot. Design A retrospecti ve epidemiological study. Animals 78,445 male cattle that entered a 24 ,000-head feedlot in western Canada from 1991 to 1993. Procedure Anima l health records for bullers were collected and analysed to see if the y were at greater risk of sickness and mortality than other steers, an d to see if pens with a high prevalence of bullers also had a high pre valence of sickness and mortality. Results The prevalence of bullers i ncreased with increasing age of cattle on arrival at the feedlot (R = 0.36; P < 0.001). Sickness and mortality decreased with increasing age of cattle on arrival. However, sickness and mortality in bullers rela tive to other steers actually increased with increasing age on arrival suggesting an interaction existed between sickness and bullers. Bulle rs were significantly (P < 0.05) more likely to get sick and to die th an other steers. In all cases, there was a strong temporal association between sickness and bullers, with sickness and bullers mostly occurr ing within the first 30 days of the feeding period. On average, pens o f cattle with a high prevalence of bullers did not have a correspondin gly high prevalence of sickness or mortality.Conclusion This study sug gests that sickness is an effect modifier of dominance behaviour and t herefore bullers in feedlot steers. Bullers should always be checked f or signs of sickness and treated accordingly. Further research is need ed to investigate the effects of sickness on dominance behaviour in pe ns of feedlot cattle.