High-Growth Rate Fails to Enhance Adaptive Immune Responses in Neonatal Calves and Decreases Immune Cell Viability

Abstract

The objective of the current study was to investigate the effects of different feeding rates achieving three targeted growth rates (No Growth, Low Growth, and High Growth) on adaptive immune responses of neonatal calves vaccinated with Mycobacterium bovis bacillus Calmette-Guerin (BCG) and ovalbumin (OVA) 3 wks after initiation of dietary treatments. The daily growth rates for No-, Low-, and High-growth calves were different throughout the experimental period and averaged 0.11 ± 0.02 kg, 0.58 ± .02, and 1.16 ± 0.04 kg, respectively. Adaptive immune responses generally were not affected by growth rate. Ovalbumin-specific IgG1 and IgG2 concentrations after vaccination were not affected by growth rate. Interferon (IFN)-γ and nitric oxide (NO) secretion by PPD-stimulated mononuclear leukocytes (MNL) also were not affected by growth rate. Antigen (i.e., PPD)-elicited delayed-type hypersensitivity in No-growth calves was greater than Lowgrowth but similar to High-growth calves. Viability of MNL, CD4+, CD8+, and γδTCR+ cells in stimulated and non-stimulated cultures from High-growth calves was substantially lower compared with No- and Low-growth calves. These results suggest protein-energy malnutrition (PEM) in the absence of weight loss does not affect negatively adaptive immune responses of calves and that increasing growth rate or plane of nutrition above maintenance requirements does not benefit adaptive immune responses. High rates of growth, however, may affect negatively immune cell viability, with potentially deleterious effects on the calf’s resistance to infectious disease.