|Brown, JR., A. - UNIVERISTY OF ARKANSAS|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 1, 1999
Publication Date: N/A
Interpretive Summary: A large proportion of stocker and feeder cattle originate in the Southeastern U.S. where a significant percentage are raised on endophyte-infected tall fescue (E+). Since E+ reduces reproduction, milk production, and weaning weights and often produces calves with characteristic long hair coats, there has been speculation that carry-over effects impact postweaning performance in calves raised on E+. Research in El Reno, OK compared postweaning performance of calves from Angus, Brahman, and reciprocal-cross cows that had been raised on E+ with similar calves raised on common bermudagrass (BG). Calves raised on E+ gained faster as stockers, were lighter in starting and finished weights on feed, had lighter carcasses and smaller ribeye areas than calves from BG. Calves from E+ were similar to calves from BG in feedlot ADG and carcass traits other than ribeye area. The advantage of three-breed cross calves compared to two-breed cross calves in postweaning weights was larger on E+ suggesting a carryover of tolerance to E+. These data suggest that few carry-over effects from tall fescue preweaning environments exist, other than lighter, but acceptable weights through slaughter. These data further suggest that in calves from Brahman-Angus cows, fewer carry-over effects from E+ are evident than in calves from purebred cows.
Technical Abstract: Calves (403) from Angus, Brahman, and reciprocal-cross cows were used toevaluate the effects of preweaning forage environment on postweaning performance. Calves were managed on either common bermudagrass (BG) or endophyte-infected tall fescue (E+) during the preweaning phase. After weaning calves were shipped to El Reno, OK and stratified to one of two winter stocker treatments, winter wheat pasture or native range plus supplemental CP. Each stocker treatment was terminated in March, calves grazed cool-season grasses and calves were then moved to a feedlot phase in June. Calves were fed to approximate 10 mm fat over the 12th and 13th rib and averaged approximately 115 days on feed. When finished, calves were weighed and shipped to Amarillo, TX for processing. Averaged over calf breed group, calves from E+ gained faster during the stocker phase (P<.10), had lighter starting and finished weights on feed (P<.01), lighter carcass weights (P<.01), and smaller ribeye areas (P<.05) than calves from BG. Calves from E+ were numerically lower in feedlot ADG (P>.25), and similar to calves from BG in percent kidney, heart and pelvic fat, fat thickness over 12th and 13th rib, yield grade, marbling score and dressing percentage. Maternal heterosis was larger in calves from E+ for starting weight on feed (P<.01), finished weight (P<.10), carcass weight (P<.16), ribeye area (P>.25), and dressing percentage (P>.35).These data suggest that few carry-over effects from tall fescue preweaning environments exist, other than lighter, but acceptable weights through slaughter. These data further suggest that in calves from Brahman-Angus cows, fewer carry-over effects from E+ are evident than in calves from purebred cows.