Animal Industry Report

Extension Number

ASL R2841



Summary and Implications

This project examined the feasibility of producing USDA Choice beef—without grain-based finishing—through genetic selection and pasture management. Purebred Angus heifers with high-marbling potential and small/medium frame size were born spring 2011. Heifers were allotted to either pasture (grass-finishing) or feedlot (grain-fed) treatments based on liveweight and intramuscular fat content. When reaching market weight (±1,000 lb) heifers were harvested and carcass data was collected. Feedlot cattle were marketed on August 27, 2012. The grass-finished cattle were marketed on November 1, 2012. Starting and end weights were similar for both treatments but feedlot cattle reached market weight 50% faster (3.9 vs 2.1 lb/day). The average intramuscular fat percent was not different at the start of the trial but there was a trend of grain-fed cattle to have greater intramuscular fat. Rib eye area, yield grade, and number grading Choice were numerically higher for feedlot cattle. This project demonstrated that it is feasible to combine high marbling genetics with pasture management to produce Choice beef in Iowa. Grass-finished cattle were able to achieve 2.1 pounds of gain per day and 60% of the grass-finished cattle ultimately graded Choice. Selection of small-framed, high-marbling potential beef cattle is essential because of the relatively low-energy density of the grass-based diet and the limited grazing season. Efforts to improve pasture quality and extend the grazing season would be beneficial to meet this goal.

Copyright Holder

Iowa State University