Impact of Maternal Heat Stress in Late Gestation on Blood Hormones and Metabolites of Newborn Calves

Impact of Maternal Heat Stress in Late Gestation on Blood Hormones and Metabolites of Newborn Calves J-R Guo, A. P. A. Monteiro, X-S. Weng, B. M. Ahmed, J. Laporta, M. J. Hayen, G. E. Dahl, J. K. Bernard, and S. Tao ABSTRACT Maternal heat stress alters immune function of the offspring, as well as metabolism and future lactational performance, but its impact on the hormonal and metabolic responses of the neonate immediately after birth is still not clear. The objective of this study was to investigate the blood profiles of hormones and metabolites of calves born to cows that were cooled (CL) or heat-stressed (HS) during the dry period. Within 2 h after birth, but before colostrum feeding, blood samples were collected from calves (18 bulls [HS: n=10; CL: n=8] and 20 heifers [HS: n=10; CL: n=10]) born to CL or HS dry cows, and hematocrit and plasma concentrations of total protein, prolactin, insulin-like growth factor-І, insulin, glucose, nonesterified fatty acid, and BHBA were measured. Compared with CL, HS calves had lower hematocrit, and tended to have lower plasma concentrations of insulin, prolactin, and insulin-like growth factor-І. However, maternal heat stress had no impact on plasma levels of total protein, glucose, nonesterified fatty acid, and BHBA immediately after birth. These results suggest that maternal heat stress desensitizes a calf’s stress response and alters fetal development by reducing the secretion of insulin-like growth factor-І, prolactin, and insulin.