An Examination of Some Physiological Variables for Assessing the Welfare of Beef Cattle in Feedlots
Some physiological variables which could aid in assessing the welfare of beef cattle in feedlots were screened in this exploratory study. In two experiments, each of 42 days duration, the physiological responses of Bos taurus steers to three treatments were investigated: pasture (rotation between 1.5 hectare paddocks); a feedlot yard stocked at 12.0 m2 per head with a dry, firm pen surface; and a 'high-density' feedlot yard stocked at 6.0 m2 per head with a wet and muddy pen surface. Fourteen steers were used per group per experiment. Relative adrenal mass in both feedlot groups was 8-10% higher than in the pasture group, and this finding was supported by morphological measurements of the adrenal glands. Out of 17 immune variables examined, only serum IgA and the T-cell lymphocytes subpopulation WC+l showed consistent differences between the feedlot and pasture groups. Interestingly, no differences were observed between the two feedlot treatments. It was concluded that although there may have been some disruption of epithelial/mucosal immunity, more support was required from other immune variables before it could be stated that the immune system was depressed and that pre-pathological states existed in the feedlot groups. However, measures of relative adrenal weight, adrenal index, serum IgA and WCl+ lymphocytes are good candidates for use in future welfare investigations of feedlot cattle.
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