Winter grazing system and supplementation of beef cows during late gestation influence heifer progeny1

Abstract

A 2 × 2 factorial arrangement of treatments was used to evaluate effects of dam winter grazing system and supplementation in the last third of gestation on subsequent BW gain, feed efficiency, and reproduction in heifer progeny. Crossbred cows (yr 1, n = 109; yr 2, n = 114; yr 3, n = 116) grazed range (WR) or corn residue (CR) during winter and within grazing treatment received 0.40 kg/d of 31% CP (DM basis) cubes (PS) or no supplement (NS). Heifer calves (yr 1, n = 56; yr 2, n = 56; yr 3, n = 54) grazed dormant pasture for 114 d postweaning and were individually fed for 87 d before a 45-d natural service breeding. Dam PS reduced (P = 0.04) heifer birth date and CR tended to increase (P = 0.07) heifer birth BW. Both PS and CR increased (P ≤ 0.05) heifer weaning BW; however, adjusted 205-d weaning BW was only lighter (P = 0.03) if the dam grazed WR with NS. Heifers from PS dams tended to be younger (P = 0.09) at puberty than NS, and there was a trend (P = 0.11) for more heifers to be pubertal by breeding if the dam grazed WR with PS compared with other treatment groups. Heifers from WR-NS dams tended to weigh less (P ≤ 0.09) at breeding and at pregnancy diagnosis than WR PS. There was a trend (P = 0.13) for pregnancy rate to be greater for heifers born to PS dams. Individually fed heifer DMI was not affected (P = 0.25) by treatment; however, heifers from dams that grazed CR with PS gained the least BW (P = 0.04) during individual feeding and had the smallest (P = 0.03) G:F. In contrast, there were no differences (P > 0.15) in feed efficiency when expressed as residual feed intake. The first calf birth and weaning BW of the heifer was unaffected (P > 0.15) by dam treatment. Heifers from dams that grazed WR with NS tended to have lighter (P = 0.09) BW before the second breeding season but similar (P = 0.97) pregnancy rates. Cows grazing CR with NS produced the most valuable heifer calf at weaning; however, heifers from cows that grazed WR with NS cost the least to develop per pregnant heifer. Winter grazing system and late gestation supplementation affected heifer progeny BW, feed efficiency, and fertility.