Effect of post-weaning management practices on physiological and immunological responses of weaned beef calves

The objectives were: i) to investigate the physiological and immunological responses of previously grazed, abruptly weaned beef calves that were then either housed (H) and offered a diet of grass silage ad libitum plus concentrate or returned to familiar pasture (P) (Phase I), and ii) to examine the effect of subsequent housing (35 days post-weaning) on these responses in P calves compared with the H calves, which were acclimated to housing (Phase II). Rectal temperature was recorded and jugular blood was collected on days 0 (weaning), 2, 7, 14, 21, 28 and 35 (Phase I) and on days 0 (housing of P), 2, 7, 14, and 21 (Phase II). There was a treatment X sampling time interaction (P<0.05) for rectal temperature, fibrinogen concentration, total leukocyte and lymphocyte number, and phytohaemagglutinin-induced interferon-y production during Phase I, with H calves having higher (P<0.05) rectal temperature and fibrino- gen concentrations on day 7, lower total leukocyte and lymphocyte number on days 7 to 35 and days 2 to 28, respectively, and reduced interferon-y production on day 7 compared with P calves. Neutrophilia (P<0.05) was present in P calves on days 2 and 7 post-weaning. In Phase II, total leukocyte and neutrophil numbers increased (P