Effects of energy intake during late pregnancy and of genotype on immunoglobulin transfer to calves in suckler herds.

Blue-Grey (Shorthorn x Galloway) and Hereford x Friesian cows were given levels of feeding, during the last 12 weeks of pregnancy, varying between 75.2 per cent and 171.5 per cent of the maintenance requirements in one experiment and between 65 per cent and 125 per cent of the maintenance requirements in a second experiment. The concentrations of the immunoglobulin classes IgG1, IgG2 and IgM, in their colostrum and in their calves' serum were measured. The IG1 and IgM, but not the IgG2, concentrations were significantly higher in the Blue-Grey than in the Hereford x Friesian colostrum and serum. The relative concentrations of the three classes in the serum were almost identical to those in the colostrum, suggesting that absorption by the calves was non-selective. The amounts of immunoglobulin transferred to the calves were not affected by the cows' levels of feeding in the first year, but there was a small increase in transfer with increasing levels of feeding during the second year. Cows that transferred large amounts to their calves in the first year tended to do so in the second year. The milk intake and growth of the calves during the first 42 days were significantly correlated with their immunoglobulin concentrations.