Postweaning and performance of calves from Angus, Brahman, reciprocal-cross tall fescue cows grazing endophyte-infected or common bermudagrass

Data from 403 Polled Hereford-sired calves from Angus, Brahman, and recipro cal-cross cows were used to evaluate the effects of preweaning forage envir onment on postweaning performance. Calves were spring-born in 1991 to 1994 and managed on either endophyte-infected tall fescue (E+) or common bermuda grass (BG) during the preweaning phase. After weaning, calves were shipped to the Grazinglands Research Laboratory, El Reno, OK and stratified to one of two winter stocker treatments by breed and preweaning forage; stocker tr eatments were winter wheat pasture (WW) or native range plus supplemental C P (NR). Each stocker treatment was terminated in March, calves grazed cool- season grasses, and calves were then moved to a feedlot phase in June. In t he feedlot phase, calves were fed to approximately 10 mm fat over the 12th rib and averaged approximately 115 d on feed. When finished, calves were we ighed and shipped to Amarillo, TX for slaughter. Averaged over calf breed g roup, calves from E+ gained faster during the stocker phase (P < .10), had lighter starting and finished weights on feed(P < .01), lighter carcass wei ghts (P < .01), and smaller longissimus muscle areas (P < .05) than calves from BG. Calves from E+ were similar to calves from BG in feedlot ADG, perc entage kidney, heart, and pelvic fat, fat thickness over 12th rib, yield gr ade, marbling score, and dressing percentage. Maternal heterosis was larger in calves from E+ for starting weight on feed (P < .01), finished weight ( P < .10), and carcass weight (P < .16). These data suggest that few carryov er effects from tall fescue preweaning environments exist, other than light er, but acceptable, weights through slaughter. These data further suggest t hat the tolerance to E+ in calves from reciprocal-cross cows, expressed in weaning weights, moderated postweaning weight differences between E+ and BG compared to similar comparisons in calves from purebred cows.