|Carroll, Jeffery - Jeff Carroll|
Submitted to: Meeting Abstract
Publication Type: Experiment Station
Publication Acceptance Date: 6/10/1998
Publication Date: N/A
Technical Abstract: The objective of this study was to determine whether genotype influences pituitary and adrenal gland function in two phenotypically diverse breeds of cattle. Multiple ovulation embryo transfer and double reciprocal backcrosses produced full-sib families of three-quarter Bos taurus (Angus; shorter, fatter, darker color and more cold tolerant) and Bos indicus (Brahman; taller, thinner, lighter color and more heat tolerant) steers from Angus and Brahman parents. From weaning steers (n=74 Brahman; n=100 Angus) were maintained in a feedlot until reaching a targeted slaughter weight (-500 kg). Blood samples were collected during exsanguination to determine concentrations of ACTH and cortisol (CS). Pituitary glands (PIT) were collected immediately following exsanguination. Total (TOT), cortical (CORT) and medullary (MED) areas of each adrenal gland were determined by computer-assisted image analysis of H&E stained sections. Mean plasma ACTH Hand CS were higher (P<.05) for Angus than Brahman steers. The anterior PI weighed more (P<.05) in Angus relative to Brahman steers. Paired adrenal weight and anterior PIT weight were positively correlated for Angus (r=.41; P<.01) and Brahman (r=26; P<.05) steers. Morphometric analysis of adrenal gland cross-sections indicated that TOT, CORT and MED area was greater (P<.05) for Angus than Brahman steers. MED and CORT regions constituted approximately 20% and 80% of the total adrenal gland, respectively, for both breedtypes. These data demonstrate that breed-type influences morphological and physiological parameters of adrenal gland function. Therefore, heredity may play an important role in controlling the mechanisms that lead to the physiological responses to stress.