Abstract
This study evaluated the correlation of immune status with age and blood component profile in Japanese Black beef steers. Thirty-seven clinically healthy 10- to 12-month-old Japanese Black steers, which were raised on four farms in Aomori Prefecture, were included in the study. Serum and plasma samples were collected every three months during the fattening period(10 to 27 months old). The number of granulocytes and CD8+ T cells was significantly higher at 16-18 and 25-27 months of age, respectively, than those at 13-15 months. The number of CD3+, CD3+/TCR1−(αβT cells) and CD4+ T cells(helper T cells) was significantly higher after 16-18 months old than the initial values. No significant change was observed in the number of CD3+/TCR1+ cells(γδT cells). The number of CD14+ cells(monocytes) was significantly lower, and the number of MHC-class II+/CD14− cells(B cells) was lower, though not statistically significant, after 16-18 months old. The number of CD3+, CD4+ and CD8+ T cells was positively correlated with age and plasma total cholesterol(TC) and negatively with plasma vitamin A(VA) , beta-carotene(β-C) and serum copper(Cu) concentrations. The number of B cells showed significant negative correlations with age and plasma TC and a significant positive correlation with plasma VA concentration. The number of monocytes was positively correlated with plasma VA, β-C and serum Cu concentrations and negatively with age and plasma TC concentration. These results revealed that aging and alterations in blood nutrient components were significantly associated with the peripheral blood leukocyte populations.
