Effects of breed and colostrum replacer quantity on lymphocyte populations in the blood of Holstein and Holstein × Angus calves.

The objective of this study was to explore the effects of breed and colostrum replacer (CR) quantity fed at birth on lymphocyte populations in the peripheral blood of Holstein (H) and Holstein × Angus (C) crossbred calves. Male H (n = 10) and C (n = 10) calves were enrolled immediately after birth and randomly assigned to one of 2 quantities of CR: low (2.5 g of IgG/kg of birth BW; n = 4 for H and 6 for C) or high (5.0 g of IgG/kg of birth BW; n = 6 for H and 4 for C). Calves were tube fed CR meals at 0 and 12 h and then fed milk replacer at an average of 12% of BW for 21 d, followed by an average of 15% of BW until gradual weaning, which occurred between d 49 and 70. Additionally, the calves had ad libitum access to both fresh water and calf starter. Fecal consistency and respiratory health were evaluated twice daily to monitor health status. Blood was collected and analyzed at 24 h using radial immunodiffusion to evaluate serum IgG concentrations. Additional blood samples were collected on d 14, 35, and 84 of life for lymphocyte isolation and staining with monoclonal antibodies against gamma delta T cell receptor, WC1.1, WC1.2, IgM, CD21, and CD32 and analyzed by flow cytometry. Serum IgG was greater for the calves fed greater quantities of CR, but there were no differences between breeds. The proportion of lymphocytes among the peripheral blood mononuclear cells tended to be greater for H calves, whereas the proportion of IgM+ and IgM+CD21+ B cells among the total lymphocytes tended to be greater for calves fed higher quantities of CR. The results suggest that the quantity of CR may alter the lymphocyte profiles in peripheral blood of calves, highlighting the importance of colostrum on the development of the immune system in early life; however, the lymphocyte profile was not found to differ between H and C calves.