Abstract
Feeder lambs (n=90) were selected from three breed types (Commercial Finewool, Suffolk X Commercial Finewool first cross (Fl cross) and Suffolk) to represent the current market supply in Texas. Three wethers and three ewes from each breed type were assigned randomly to one of five yield grade treatment groups (n=18), devised to simulate the fat thickness ranges designated by the USDA yield grade equation. The lambs were evaluated periodically and visually appraised by a team of three experienced livestock evaluators. They were slaughtered at staggered intervals, according to the Humane Methods of Slaughter Act, when the evaluators had determined that an individual lamb had reached its assigned fat thickness. Before slaughter, certain linear measurements were obtained for each lamb, and live weights were recorded. All carcasses were evaluated for USDA quality and yield grade characteristics by trained carcass evaluators at 48 h postmortem. Additional carcass measurements and characteristics were recorded. Carcasses were fabricated into a rough leg, rough loin, rough rack, rough shoulder, neck, right and left breasts, right and left plates. Kidney and pelvic fat (KP) was removed from the rough leg and rough loin following breaking. The rough primals were then split into left and right sides, and the leg, loin, rack, and shoulder from the left side of the carcass were fabricated into closely trimmed retail cuts, lean trim, bone, and fat (external, seam, and internal). Yield grade class was significantly related to the weight and percentage of retail product and to the percentage of trimmable components. Additional live and carcass measurements revealed significant correlations with these weights and percentages. Regression equations offered higher predictive values when estimating weight rather than percentage of retail product. As days on feed and live weight increased, yield grade class, along with weight and percentage of trimmable fat, also increased.
Fritz, Kristina Danielle (1996). The role of yield grade and fat deposition on the cutability of lamb carcasses. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1996 -THESIS -F75.