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Effect of winter distillers grains supplementation level on spayed heifer performance
A two-yr study was conducted utilizing 220 spayed heifers (BW=234; SD=23 kg) each yr to determine the optimal level of modified distillers grains plus solubles (MDGS) supplementation during winter grazing. The 2 yr of data were analyzed separately due to variation in summer gains by yr. Treatments included the supplementation of MDGS at 1.36, 2.27, and 3.18 kg heifer daily during the winter corn residue grazing phase. Following winter grazing for 150 d, heifers grazed smooth bromegrass for 30 d and native range for 120 d. Heifers were then finished on a common ration. For both yr, ending BW and ADG for the winter phase increased linearly (P < 0.01), and summer phase ADG decreased linearly (P < 0.01) as winter supplementation level increased. For yr 1, ending BW for summer was not different (P = 0.36) however, yr 2 summer ending BW increased linearly (P < 0.01) from 415 to 433 kg as winter supplement increased. For yr 1, there were no differences (P ≥ 0.30) in finishing performance and total system ADG (average of winter, summer, and finishing) was not different (P = 0.91) among treatments. In yr 2, final BW linearly increased (P = 0.04) from 591 to 616 kg due to winter MDGS supplementation. For both yr, ADG and G:F were not different (P ≥ 0.25) during the fall finishing phase. Year 2 total system ADG linearly increased (P = 0.02) from 0.83 to 0.89 kg/d as MDGS supplementation increased during the previous winter. There were no differences in carcass characteristics (P ≥ 0.27) for yr 1. However in yr 2, HCW increased linearly (P = 0.04) from 372 to 388 kg as winter supplementation increased. Similar with yr 1, there was no difference in LM area (P = 0.23) or marbling score (P = 0.28). Contrary to yr 1, there was a linear increase (P = 0.04) in 12th rib back fat thickness and consequently a tendency for linear increase in calculated yield grade (P = 0.10) as heifers were supplemented with increasing levels of MDGS in the winter phase. Level of winter supplementation had no effect on finishing ADG or G:F when backgrounded on summer grass without supplement prior to feedlot arrival. However, greater levels of supplementation increased total system gain when summer grazing is not limited. Supplementing heifers at 3.18 kg/d MDGS during winter corn residue grazing has the potential to increase HCW.
Keywords: spayed heifer, supplementation, distillers grains