Effects of Prenatal Stress on Insulin Sensitivity, Physiological Stress Responses, Growth, and Temperament of Brahman Calves
Schmidt, Sarah Erin
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Stress incurred due to standard management practices applied to pregnant cattle may affect the health and productivity of the offspring. Separate studies were conducted to determine: 1) the extent to which transportation of cattle between 60 and 140 days of gestation affects the subsequent calves? endocrine stress response and insulin sensitivity, and 2) whether a chronic stressor applied during late gestation alters the birth weight, growth, or temperament of the offspring of Brahman cattle. The function of the hypothalamic-pituitary-adrenal axis was studied with the use of intravenous ACTH and intravenous CRH challenges in 12 Brahman yearling heifers born to dams that were transported for 2 hours at 60, 80, 100, 120, and 140 days of gestation (prenatally stressed) and 12 yearling heifers whose dams were not transported (control). Prenatally stressed heifers did not differ from controls in their cortisol response to ACTH over time (P = 0.12) or in the cortisol (P = 0.12) and ACTH (P = 0.90) responses to CRH. The same group of heifers was also evaluated for insulin sensitivity and ability to clear circulating glucose with the use of an intravenous glucose tolerance test. Prenatally stressed heifers showed a decreased insulin response over time to the glucose bolus (P = 0.03), but did not differ from controls in serum glucose concentration over time (P = 0.61). The prenatally stressed heifers also took longer to reach peak insulin concentrations following the glucose challenge (P < 0.01) and returned to basal serum glucose and insulin concentrations in a shorter amount of time (P < 0.01). A group of 13 multiparous cows and 20 nulliparous heifers was subjected to the Callicrate band dehorning procedure between days 93 and 168 of gestation. A control group consisting of 27 parous cows and 5 nulliparous heifers was not dehorned. The offspring produced by these cattle were evaluated for birth weight, temperament, and growth. The prenatally stressed calves (from the banded group) in this study had decreased birth weight (P = 0.04) compared to the control calves. However, the groups of calves did not differ in either temperament or growth at any point from 14 d of age through weaning. In summary, it appears that a repeated transportation stressor applied between 60 and 140 days of gestation alters the insulin sensitivity, but not pituitary or adrenal function, of Brahman heifer calves. Additionally, a stressor applied later in gestation does not appear to have lasting effects on the growth or temperament of calves.