Submitted to: Western Section of Animal Science Proceedings
Publication Type: Proceedings
Publication Acceptance Date: June 1, 2012
Publication Date: July 15, 2012
Citation: Endecott, R.L., Shipp, B.L., MacNeil, M.D., Alexander, L.J., Roberts, A.J. 2012. Postweaning feed restriction effects on steer feedlot performance and carcass characteristics. Western Section of Animal Science Proceedings 63:258-261. Interpretive Summary: Harvested feedstuffs are a major input cost for range-based cow-calf producers. A long term study at Fort Keogh has evaluated the influence of 2 levels of nutritional input during heifer development (ad libitum or 20% less feed) and winter supplementation (adequate or marginal) on lifetime productivity in beef females. Bull calves in this experiment also received 2 levels of nutritional input during the postweaning period, but little work has been done to assess feedlot performance and carcass characteristics of these calves. Therefore, the objective of this research was to evaluate the impacts of 2 levels of supplemental feed provided to cows during late gestation and 2 levels of feed provided to their sons during postweaning development on subsequent feedlot performance and carcass characteristics. Calves restricted during the postweaning period gained more weight while eating the same amount of feed during the finishing period compared to calves fed ad libitum during the postweaning period, and steers had some similar carcass characteristics regardless of postweaning treatment. Restricted appeared to compensate for the nutritional restriction when it was removed, although they were still somewhat lighter than the Control steers at harvest. These results imply that the amount of harvested feedstuffs used in cow-calf production could be reduced with limited negative impact on beef production and quality.
Technical Abstract: The objective was to evaluate impacts of 2 levels of supplemental feed provided to cows during late gestation and 2 levels of feed provided to their sons during postweaning development on subsequent feedlot performance and carcass characteristics. Bull calves (n = 56 in 2010; n = 51 in 2011) were born from dams receiving adequate (1.8 kg/d) or marginal (1.2 kg/d) winter supplementation. After weaning, bulls were developed on ad-libitum (Control) or 27% less feed (Restricted) for ~140 d. Bulls were then band-castrated and placed on an 80% corn finishing diet ad libitum. Individual intakes were measured with a GrowSafe system for the final 100-150 d of the finishing period. Cattle were harvested at a commercial packing plant and carcass data were collected. Dam winter supplementation effects were not detected (P = 0.22). Postweaning phase ADG exhibited a postweaning treatment × year interaction (P < 0.01). Restricted calves had similar ADG in both years (0.64 vs 0.68 ± 0.03 kg/d) and gained less than Control calves. Control calves had greater ADG in 2010 than in 2011 (1.16 vs 1.03 ± 0.03 kg/d). Postweaning treatment did not impact feed intake during the finishing phase (P = 0.29; 13.0 vs 12.8 ± 0.22 kg/d for Restricted vs Control; as-fed basis). During the finishing phase, ADG exhibited a postweaning treatment × year interaction (P < 0.01). Restricted steers had similar ADG in both years (1.25 vs 1.27 ± 0.05 kg/d) and gained more than Control steers. Control steer ADG was less in 2010 than in 2011 (0.92 vs 1.13 ± 0.05 kg/d). Compared to Control steers, Restricted steers had lower (P = 0.08) final BW (603 vs 623 ± 9 kg), HCW (357 vs 373 ± 6 kg), and yield grade (2.71 vs 2.89 ± 0.10). However, back fat thickness (1.09 vs 1.14 ± 0.05 cm), ribeye area (85.4 vs 85.8 ± 0.98 cm2), and marbling score (5.59 vs 5.50 ± 0.12) were not different (P = 0.34). Calves restricted during postweaning development gained more efficiently, and when harvested on a common date, had lower carcass weights and yield grade, but similar fat thickness, ribeye area and quality grade compared to their ad libitum-fed counterparts.