|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 gland development and/or somatotroph number and size in two phenotypically diverse breeds of cattle. Multiple ovulation embryo transfer and double reciprocal backcrosses produced full-sib families of 3/4 Bos taurus (Angus; shorter, fatter, darker color and more cold tolerant) and Bos indicus (Brahman; taller, thinner, lighter color and mor 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). Growth parameters and carcass characteristics [i.e., average daily gain (ADG); ribeye area (REA); dressing percent (DP); hip height (HHT)] were recorded for each steer from birth to slaughter. Blood samples were collected during exsanguination to determine plasma concentration of growth hormone (GH). Pituitary glands (PIT) were collected immediately following exsanguination. REA, PIT and anterior PIT were greater (P<.001) in Angus than in Brahman steers, although DP and HHT were greater (P<.03) in the Brahman steers. Plasma concentration of GH at slaughter and GH cell size (average area of 900 cells/ANT PIT) did not differ (P>.10) for Angus versus Brahman steers (194 +/ 2.1 and 198 +/ 2.2 sq microns, respectively). The number of GH cells/sq mm ANT PIT was greater (P<.01) in the Brahman versus Angus steers (1938 +/ 94 and 1625 +/ 58, respectively). Phenotypic variation among cattle breeds (i.e., deposition of lean and adipose tissue) may directly reflect genotypic differences in the somatotrophic axis (i.e., enhanced somatotroph recruitment/function).