The neonatal calf is especially prone to enteric and respiratory infections during the first two to three months of life. The mortality rate and disease incidence are of enormous economic importance in the production of calves. The innovation of embryo transfer techniques has made it possible to produce twin calves from both dairy and suckler cattle, therefore the health and survival of these calves is of prime importance to the viability of twin calf production. The neonatal calf relies upon three mechanisms for protection against pathogens; the barrier provided by mucus secreting epithelial cells; the non-specific engulfing of foreign antigenic material by phagocytic cells and the immunoglobulins received via the colostrum. Neonatal calves are born with low levels of β-carotene and essential fatty acids (Noble, 1984) which have both been shown to be important for the health and performance of a number of animal species (Bendich and Shapiro, 1986) and may enhance the immune response in newborn animals.