Opportunities for selection to improve steer and cow productivity in northern Australia

Abstract

This thesis analysed carcass records from 2180 tropically adapted, steers (986 Brahman (BRAH) and 1194 Tropical Composite (TCOMP)) describing weight, eye muscle area, P8 and 12/13th rib fat depth, percent intramuscular fat and retail beef yield, with tenderness assessed as shear force. All steers were feedlot finished with a subset (680 BRAH and 783 TCOMP) recorded for individual feed intake. Female reproductive performance in the half-sib sisters of these steers (1007 BRAH and 1108 TCOMP) was evaluated as outcomes of their first (Mating 1: when females averaged 27 months of age) and second (Mating 2) annual matings, and averaged over up to 6 matings (termed 'lifetime' reproduction traits). Heifer and cow weight, eye muscle area, P8 and 12/13th rib fat depth, body condition score and hip height were recorded at 18 months of age, immediately prior to first calving and at Mating 2. The maternal genetic component of weaning weight (Maternal WWT) was estimated based on weaning weight records available for these steers and females and the progeny of females (N = 12528).