Effects of Ration Energy Level on Organoleptic and Chemical Characteristics of Beef.

Abstract

Four experiments were conducted to evaluate carcass characteristics, palatability, chemical traits and shear values of cattle produced on pasture (primarily bermudagrass and ryegrass), pasture plus 1/2% or 1% of body weight in grain or finished on a concentrate ration. Angus or Angus x Hereford cattle were used in Experiments 1, 2 and 3 but Experiment 4 contained straightbred Angus and Hereford along with crosses of Angus, Hereford, Brahman and Charolais cattle in various combinations. Age at slaughter was 23 and 20 months for Experiments 1 and 2, respectively. Age in Experiments 3 and 4 varied with treatments because of the experimental design. Number of animals per treatment varied from 10 to 24 among the four experiments. Carcass data were taken for all animals. An 18 cm portion of the blade chuck, the short loin (tenderloin removed) and the top round from one side were cut, wrapped and frozen at -16 C for distribution to consumer panels in Experiments 1, 2 and 3. Loin, chuck, rib, round, rump and sirloin cuts were delivered to cooperating retail food stores for fabrication into retail cuts used in the retail study. Loin steaks, rib roasts and round steaks were cut and frozen for laboratory panel evaluation in Experiment 2. Ribeye steaks were obtained from each carcass in Experiment 4 for laboratory panel evaluation. Fat samples for rancidity (thiobarbituric acid) and fatty acid analysis were taken from subcutaneous fat above the longissimus muscle. Loin steaks were used in Experiments 1, 2 and 3 for evaluation of pH and shear. Forage-fed cattle in Experiment 1 had less fat thickness than cattle fed 1/2% grain-on-grass or fed concentrate free-choice for 63, 78 or 108 days. Evaluation of chuck, loin and round steaks by a 150 household consumer panel showed panelists preferred (P < .05) the loin steaks from grain-fed treatments over limited grain or forage treatments for tenderness and flavor. The forage treatment also had a higher (P < .05) pH than treatments receiving grain. There were significant differences (P < .01) for all carcass characteristics in Experiment 2. Differences were usually between the forage treatment and the grain-fed treatments (1% grain-on-grass, 70 to 140 day feedlot treatments). A 273 household consumer panel found chuck steaks to be less (P < .05) tender and loin steaks to be less (P < .05) juicy from forage-fed cattle compared to grain-fed cattle. Fewer treatment differences were observed in consumer