Fattening on pasture of beef calves differing in muscle thickness, frame size and apparent Brahman genotype subjected to implant and supplementation regimes

Abstract

Growth data of two separate groups of 52 (group I) and 85 (group II) grazing cattle were analyzed using least squares analyses of variance-covariance for average daily gain (ADG), body weight:height ratio (WHR) and final live weight (FLW) as affected by muscle thickness (thick, intermediate, or thin), frame size (large, medium, or small) and apparent Brahman genotype (50, 75 or 100% Brahman), supplementation on pasture (supplemented vs control groups) and/or implant regime in group II (1XRevalor®-2XRalgro® vs 2X Ralgro®-2X Ralgro®) and their respective interactions. Muscle thickness did not affect growth traits (P>.05). In group I medium-sized calves advantaged 16.2 kg in FLW to their smallsized counterparts. Supplementation treatment affected favorably ADG, WHR and FLW whereas the apparent Brahman genotype did not show significant effect on growth performance. The muscle thickness x supplementation interaction showed that within the supplemented group, calves with intermediate musculature had higher (0.17 kg/cm more)WHR than those with thin musculature (P<.05). In group II, the large-framed cattle had higher height (>3.5 cm) and heavier FLW (>25.4 kg) than medium- and small-framed cattle; the supplemented cattle had superior (P<.01) stature and the 100% Brahman with 3.6 cm were lighter in FLW (464 kg). Implant regime had no effect on growth traits (P>.05). The frame size x supplementation interaction affected (P>.05) FLW and WHR (within the supplemented group large-framed >mediumframed>small-framed cattle). Frame size allowed for anticipating the future growth performance of grazing calves and the biological response could be improved by the supplementation treatment.