Colostrum programs early t lymphocyte-mediated immunity in neonatal dairy calves: effects of deprivation and preservation method on passive transfer and antigen-specific responses.

This study evaluated how colostrum intake and processing influence passive antibody transfer and vaccine-induced humoral and cell-mediated immune responses in neonatal calves. Twenty-four Holstein cows were vaccinated with an experimental Salmonella Dublin siderophore receptor protein (SRP) vaccine, and their calves were assigned to receive fresh colostrum (FSH, n = 8), frozen colostrum (FZN, n = 8), or no colostrum (DPR, n = 8). Calves were subsequently vaccinated with the same SRP antigen on d 7, 28, and 70 of life. Blood samples collected during the first 12 weeks of life were analyzed for total serum IgG, SRP-specific IgG, T-lymphocyte proliferation, and IFN-γ production. Colostrum-fed calves achieved successful passive transfer of total and SRP-specific IgG at 24 h of age (P < 0.01), with no differences between FSH and FZN. Maternal antibody interference persisted into the post-weaning period: even after the third vaccine dose at d 70, colostrum-fed calves had lower SRP-specific antibody titers than DPR calves (P = 0.05). Cellular responses followed a selective rather than global pattern: DPR calves showed an exaggerated CD8+ proliferative response to the SRP antigen at d 2 (P = 0.04) but no difference in response to Concanavalin A, indicating an antigen-specific rather than generalized phenotype. Among colostrum-fed groups, FSH had lower CD4+ and γδ proliferation against SRP than FZN; however, IFN-γ production was unaffected by treatment. These findings show that colostrum and its processing influence both the humoral and cellular arms of pathogen-specific adaptive immunity in early life, and that the cellular effects are selective for antigen-specific proliferation. Maternal antibody interference can persist well beyond the post-weaning window, suggesting that booster vaccination protocols in colostrum-fed calves may need to extend beyond the conventional timeline to overcome this interference. Together, these results highlight colostrum management and dry cow vaccination as key determinants of adaptive immune development in dairy calves.