Comparison of immune responses in calves fed heat-treated or unheated colostrum.

Understanding the mechanisms that underlie neonatal immune function is important for appropriately treating and preventing disease. Cytokines provided in colostrum may affect immune development and function, but data describing cytokine absorption in calves and the effects of colostrum heat treatment on absorption are limited. The objectives of this experiment were to characterize immune responses in calves that received heat-treated (HT) or unheated (UH) colostrum (in terms of growth, rectal temperature, and blood cytokine and IgG concentrations) and to determine calves' ability to absorb IFNγ and IL1β from HT and UH colostrum. A single large batch of colostrum was divided to create treatments. The HT colostrum was heated to 60°C for 60 min. Both treatments were frozen until needed and warmed immediately before feeding. Bull calves (n = 26) were randomly assigned to receive 8% of their birth weight in colostrum from 1 treatment at birth. Blood was collected at 0 and 24 to 48 h after birth for IL1β, IFNγ, and IgG analyses. Subcutaneous injections of ovalbumin (5.0 mg/mL) were given at 14 and 35 ± 3 d of age. Rectal temperature and growth were monitored for 10 d following each injection. Plasma samples were collected at 0, 4, 8, and 12 h post-injection and daily for the subsequent 10 d to measure IL1β, IFNγ, and IgG concentrations. Colostrum heat treatment failed to increase blood IgG concentrations or the apparent efficiency of IgG absorption. Serum IL1β concentrations were higher in UH calves 24 to 48 h after birth and remained higher than those in HT calves through 15 d of age. Both IFNγ and IgG increased in response to ovalbumin injection; we observed no differences between treatments. Rectal temperature increased and peaked 12 h after injection at 14 and 35 d. Growth rate was reduced by exposure to the foreign antigen. Interactions of calf age and colostrum treatment with time post-injection indicate that calves tended to show greater loss in average daily gain at 35 d than at 14 d, and UH calves tended to recover greater rates of growth 6 to 10 d after receiving ovalbumin injection. Thus, feeding HT colostrum did not inhibit neonatal immune response, but it may have affected recovery from exogenous antigen challenge.