Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 21, 2005
Publication Date: February 16, 2006
Citation: Phillips, W.A., Coleman, S.W., Riley, D.G., Chase, C.C., Mayeux, H.S. 2006. Stocker and feedlot performance and carcass characteristics of purebred Angus and Romosinuano steers. Professional Animal Scientist. 22:8-13. Interpretive Summary: The majority of the calves born in the southern United States will be shipped to a more temperate environment for growth and development before entering the feedlot for finishing. Romosinuano, a tropically adapted beef breed from Columbia, is being investigated as a new source of genetic tolerance to heat for inclusion into southern United States beef herds. Romosinuano steers gained less weight during the winter than Angus steers when calves were grazing wheat pastures. When moved to a feedlot in the summer for finishing, performance was similar, but Angus steers produced higher quality carcasses with more marbling than the Romosinuano steers. Based on this study, Romosinuano can be used in a crossbreeding program to gain genetic tolerance to heat stress without dramatically impacting stocker and feedlot performance.
Technical Abstract: Stocker and feedlot performance of purebred Angus and Romosinuano steers were compared over two production cycles. Calves were born in the winter and reared in a subtropical environment (central Florida), weaned in the fall and shipped (1900 km) for growth and finishing in a more temperate environment (central Oklahoma). Calves were managed as a single group during the winter (125 d) and spring (84 d) stocker phases. Annual cool season grasses, Triticum aestivum and Bromus sp., were the primary forage resource for the stocker phase. Angus and Romosinuano calves had similar BW upon arrival (193 kg ± 3.5). During the winter stocker period, Romosinuano calves gained less (P < 0.05) BW than Angus steers (75.9 vs 102.2 kg) and had lower (P < 0.05) total gain(118.3 vs 143.8 kg) during the stocker phase. In June of each year at the end of the stocker phase, calves were blocked by breed and randomly assigned to a conventional confinement or a grain-on-grass (GOG) finishing system. In the GOG system steers were finished on bermudagrass pasture using a combination of intensive stocking rate (9 calves/ha) and ad libitum access to a high energy diet in a self-feeder. Angus steers were heavier (P < 0.05) at the start of the finishing period and produced carcasses that had higher (P < 0.01) marbling scores, yield grades and quality scores than Romosinuano steers. Under conventional confinement feeding, Romosinuano steers had lower (P < 0.10) DMI than Angus steers, but feed efficiencies were similar. Calves finished under the GOG system produced leaner carcasses than calves finished under the conventional system with 71 kg less (P < 0.10) total supplemental feed. Under a temperate production environment, purebred Romonsinuano steers will have lower ADG during the winter and will produce leaner carcasses than purebred Angus steers. A pasture finishing system, which used a combination of intensive early stocking on bermudagrass followed by ad libitum access to a high energy diet, produced leaner carcasses with less supplemental feed input as compared to confinement feeding.