Winter grazing system and supplementation during late gestation influence performance of beef cows and steer progeny ¹

ABSTRACT

A 2 × 2 factorial study evaluated effects of cow wintering system and last trimester CP supplementation on performance of beef cows and steer progeny over a 3-yr period. Pregnant composite cows (Red Angus × Simmental) grazed winter range (WR; n = 4/yr) or corn residue (CR; n = 4/yr) during winter and within grazing treatment received 0.45 kg/d (DM) 28% CP cubes (PS; n = 4/yr) or no supplement (NS; n = 4/yr). Offspring steer calves entered the feedlot 14 d postweaning and were slaughtered 222 d later. Precalving BW was greater ( P = 0.02) for PS than NS cows grazing WR, whereas precalving BCS was greater ( P < 0.001) for cows grazing CR compared with WR. Calf birth BW was greater ( P = 0.02) for CR than WR and tended to be greater ( P = 0.11) for PS than NS cows. Prebreeding BW and BCS were greater ( P ≤ 0.001) for CR than WR cows and PS than NS ( P = 0.006) cows. At weaning, CR cows were heavier ( P < 0.001) than WR cows but had similar BCS ( P = 0.74). Cow weaning BW and BCS were not affected ( P > 0.32) by PS. Calf weaning BW was less ( P = 0.01) for calves from NS cows grazing WR compared with all other treatments. Pregnancy rate was unaffected by treatment ( P > 0.39). Steer ADG, 12th-rib fat, yield grade, and LM area ( P > 0.10) were similar among all treatments. However, final BW and HCW ( P = 0.02) were greater for steers from PS-WR than NS-WR cows. Compared with steers from NS cows, steers from PS cows had greater marbling scores ( P = 0.004) and a greater ( P = 0.04) proportion graded USDA Choice or greater. Protein supplementation of dams increased the value of calves at weaning ( P = 0.03) and of steers at slaughter regardless of winter grazing treatment ( P = 0.005). Calf birth and weaning BW were increased by grazing CR during the winter. Calf weaning BW was increased by PS of the dam if the dam grazed WR. Compared with steers from NS cows, steer progeny from PS cows had a greater quality grade with no ( P = 0.26) effect on yield grade. These data support a late gestation dam nutrition effect on calf production via fetal programming.