|Brown, A - UNIVERSITY OF ARKANSAS|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 15, 2001
Publication Date: January 15, 2001
Citation: PHILLIPS, W.A., BROWN, M.A., BROWN, A.H., COLEMAN, S.W. 2001. GENOTYPE X ENVIRONMENT INTERACTIONS FOR POSTWEANING PERFORMANCE In CROSSBRED CALVES GRAZING WINTER WHEAT PASTURE OR DORMANT NATIVE PRAIRIE. JOURNAL OF ANIMAL SCIENCE. Volume(79): p. 1370-1377. Interpretive Summary: In the fall producers in the southern Great Plains buy calves to graze winter wheat pasture, but the number of stockers needed is difficult to accurately anticipate. To take advantage of the abundant supply of calves in the fall, producers can purchase more stockers than needed, place as many as possible on fall wheat forage production, and winter the rest on dormant native prairie until the spring when wheat forage production increases 4-fold and additional stockers are needed. The objective of this experiment was to determine the impact of stocker wintering system on subsequent stocker performance, feedlot gains and carcass quality. A total of 403 calves of four different breed combinations were used over four grazing seasons. Although stockers wintered on native prairie gained less weight during the winter than their contemporaries on winter wheat, these stockers had greater rates of gain when placed in the feedlot. Under rthis management system producers would have to retain ownership through th finishing phase to realize maximum calf performance. Although all calves were sired by Hereford bulls, calves from purebred cows gained weight more rapidly during the winter than calves from crossbred cows. This was especially true for calves wintered on native prairie. Stocker producers should match stocker wintering program with the proper stocker genetics to maximize calf performance.
Technical Abstract: Data from 403 calves were used to evaluate the impact of postweaning backgrounding forages on postweaning weight, gains, and carcass traits. After weaning, calves were assigned to one of the following winter stocker treatements; 1) winter wheat pasture (WW) or 2) dormant native prairie plus supplemental CP (NP). Winter stocker treatments were ended in March and all calves grazed the same cool-season grasses until June. Calves were then fed a high concentrate diet. Calves from WW gained faster (P<.01) during the stocker phase (.71 vs .43 kg), had heavier (P<.01) final feedlot weights (535 vs. 512 kg), lower feedlot (P<.01) ADG (1.37 vs 1.53 kg), heavier (P<.01) carcass weights (337 vs 315 kg), larger (P<.01) Longissimus muscle (84.9 vs 81.8 cm2), higher percent (P<.01) kidney, heart and pelvic fat (62.3 vs 61.3), and higher (P<.01) dressing percentage (62.2 vs 61.3) than calves backgrounded on NP. Calves from WW were similar to calves from mNP in fat thickness over the 13th rib (12.1 vs 11.8 mm; P>.49), and yield grade (2.8 vs. 2.7;P>.20), but numerically higher in marbling score (3.75 vs 3.66;P<.14). Maternal heterosis for stocker ADG was evident in calves backgrounded on NP but not on WW (P<.10), but the two environments were similar in maternal heterosis for feedlot ADG and carcass traits. Calves wintered on NP expressed compensatory gain during the feedlot phase, but not during the spring stocker phase. These data suggest that expression of maternal heterosis for weight gain is more likely in calves backgrounded on native prairie and that native grasses can be used to winter calves excess to the fall wheat pasture needs. However, calves wintered on NP would have to be retained through the feedlot phase to realize any advantage of built in compensatory gain.