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 matter milk substitute powder per day) and three ages of weaning (five, nine and 13 weeks) on cellular immune responses were determined in 32 calves. The lower level of nutrition was found to increase skin sensitivity responses to keyhole limpet haemocyanin (KLH) and decrease lymphocyte blastogenesis test (LBT) responses to ConA and pokewood mitogen (P < 0.05). Weaning at five weeks old resulted in increased KLH skin responses at nine weeks old compared with unweaned calves and decreased LBT responses to ConA and phyto-haemagglutinin at 10 weeks old compared with calves weaned at nine weeks old (P < 0.05). Weaning at five weeks old also increased peripheral blood concentrations of BoCD2+ and BoCD8+ lymphocytes (P < 0.05). The results show that the choice of husbandry conditions alters cellular immune responses in young calves and suggest that early weaning effects are essentially nutritional.