Stress Response at different Ages of Weaning in Cattle

Abstract

Weaning is an inherent husbandry practice incow-calf beef production systems that impose physical,psychological, and nutritional stressors on calves. In orderto characterize the main stressors and corresponding stressresponses of calves, two weaning schemes were studied.One of conventional weaning (6 month calves) and anotherof early weaning (1 month calves). Blood samples wereanalyzed in an hematology analyzer, the plasma wasseparated and an analysis of total protein and of cortisollevels was carried. Finally, the response to a vaccine wasassessed by analyzing antibody response titers. Asignificant decrease in the number of lymphocytes andincrease in the number of granulocytes was observed in theconventionally weaned group leading to an elevated GR:LYratio. On day one post-weaning, plasmatic proteins showeda significant increase of similar range in both groups. Withregard to cortisol levels, there was a strong increase at dayone corresponding to a clear stress response in theconventional weaning group, wheras in the group of earlyweaning animals only a marginal increase which difficultreturned to baseline levels could be observed. As to theantibody response to vaccination, early weaning animalsdid not show a satisfactory response as was observed incalves subjected to conventional weaning. In conclusion,leukocyte subsets, plasmatic proteins, cortisol levels, andimmune status were altered after weaning challenge in bothstudied age groups of calves. Results indicate weaning as astressor, regardless of age.