ALTERATION OF CELLULAR IMMUNE-RESPONSES BY NUTRITION AND WEANING IN CALVES

The effects of two levels of nutrition (400 g and 1000 g air dry matte r milk substitute powder per day) and three ages of weaning (five, nin e and 13 weeks) on cellular immune responses were determined in 32 cal ves. The lower level of nutrition was found to increase skin sensitivi ty responses to keyhole limpet haemocyanin (KLH) and decrease lymphocy te blastogenesis test (LBT) responses to ConA and pokewood mitogen (P< 0.05). Weaning at five weeks old resulted in increased KLH skin respon ses at nine weeks old compared with unweaned calves and decreased LBT responses to ConA and phyto-haemagglutinin at 10 weeks old compared wi th calves weaned at nine weeks old (P<0.05). Weaning at five weeks old also increased peripheral blood concentrations of BoCD2+ and BoCD8+ l ymphocytes (P<0.05). The results show that the choice of husbandry con ditions alters cellular immune responses in young calves and suggest t hat early weaning effects are essentially nutritional.