Cow carcasses (n = 60) were selected based on conformation and external fat to develop more current and useful prediction equations for estimating yield and composition. Adjusted preliminary yield grade was highly correlated to percentage of the carcass as fat (.91), percentage fat in the total lean (.89), and percentage fat in the lean trimmings (.88) of carcasses from non-grain-fed mature cows. Equations for predicting percentage of the carcass as chemical fat had higher -R2 values than equations predicting other compositional end points. The "best" regression equation for predicting total yield (i.e., whole muscle cuts plus lean trimmings adjusted to 10% chemical fat) included hot carcass weight (HCWT), adjusted preliminary yield grade (APYG), longissimus area (LMA), and marbling (MARB), with R2 = .75 and residual standard deviation (RSD) = 2.47. A similar equation predicting total yield from unribbed carcass data included HCWT, APYG, and conformation (CONF) with R2 = .69 and RSD = 3.11. These two equations were applied to a test group of cow carcasses (n = 20), and the average difference between the actual and predicted total yield values from ribbed data and unribbed data was .45 and .83% of HCWT; simple correlations between the actual and predicted values were .74 and .69, respectively. These equations contain relatively simple independent variables to identify and more nearly represent current industry processing practices than equations previously available.

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Carcasses from 59 steers produced from the mating of Braford, Simbrah, Senepol, and Simmental bulls to Brahman- and Romana Red-sired cows and Brahman bulls mated to Angus cows were used in this study. Effects of sire breed and feeding calves vs yearlings on fat depots in the chuck, when steers were fed to 1.0 cm external fat, were determined. Breed of sire and feeding calves vs yearlings had no effect (P greater than .05) on percentage of intermuscular fat. However, carcasses from Braford-sired steers had a higher (P less than .05) percentage of dissectable subcutaneous fat on the chuck than did those from other breed groups. Carcasses from Simmental-sired steers were superior (P less than .05) to those from Braford-sired steers in USDA yield grade and had a higher average marbling score (P less than .05) than the Simbrah-sired group. Estimated kidney, pelvic, and heart (KPH) fat was higher (P less than .05) in carcasses from Brahman-, Simbrah-, and Senepol-sired steers than in Braford-sired steers. Steers fed as calves had higher percentages (P less than .05) of KPH fat and major chuck muscles than did those fed as yearlings. The best single predictor of percentage of intermuscular fat within the chuck was adjusted fat over the ribeye (R2 = .46).

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