Associations between immune system, growth and carcass variables in cattle

Abstract

A range of haematological and immunological variables was measured in calves to assess relationships between these factors and effects of maternal and pre-weaning supplementation on meat quality. The ability of immunological and haematological measurements to predict both weight loss during transport and meat quality was also examined. Calves from supplemented cows had higher counts of lymphocytes bearing the γδ T cell receptor [workshop cluster (WC)1+ lymphocytes]. When cultured in vitro, lymphocytes from calves supplemented directly produced higher levels of the cytokine interferon (IFN)γ. These changes may reflect a greater resilience to the effects of stress associated with routine handling for weighing and blood sampling, or earlier maturation of the immune system in supplemented calves. Two calves from unsupplemented treatments died of calf diphtheria before weaning. During feedlot finishing, the prevalence of disease was low and did not differ between groups. The prevalence of cluster of differentiation (CD)4+ lymphocytes in blood was correlated with growth rates from weaning to slaughter and during feedlot finishing. Lymphocyte counts and the ratio of neutrophils to lymphocytes in blood collected either before or after transport was correlated with weight change during transport. These variables were not correlated with meat quality, however the numbers of lymphocytes after transport in the subset bearing the CD8 marker was correlated with the meat quality traits, tenderness, juiciness, flavour, overall likability, meat quality (MQ) 4 score and Meat Standards Australia (MSA) grade ratings. The results demonstrate that lymphocyte subpopulations are associated with growth rate, weight loss during transport, and meat quality. Their utility in predicting performance, stress tolerance, and meat quality therefore, warrants further investigation.