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Palatability of steaks from young bulls that had or had not been electrically stimulated (ES) and steers that had not been electrically stimulated (non-ES) were compared. Steaks from non-ES young bulls, as compared with steaks from matched (for marbling and skeletal maturity) steers, had lower (P<.05) tenderness and connective tissue ratings and higher (P<.05) shear force values. Steaks from U.S. Choice steers and from U.S. Good steers or bulls that had at least 7.6 mm fat thickness did not differ (P>.05) in 28 of 30 possible comparisons of palatability characteristics. Steaks from U.S. Standard bulls and steers and U.S. Good bulls and steers that had less than 7.6 mm fat thickness were less palatable than steaks from U.S. Choice steers or from U.S. Good bulls and steers that had at least 7.6 mm fat thickness. These data indicate that the USDA might well give further consideration to a revision of its beef grade standards that would permit “A” maturity carcasses with a “slight amount” of marbling and at least 7.6 mm fat thickness to grade U.S. Choice, irrespective of their sex class.

Effects of electrical stimulation (ES), subcutaneous fat thickness and carcass masculinity on quality-indicating characteristics and palatability of beef from young bulls were evaluated. Electrical stimulation improved lean maturity (P<.0001) and overall maturity (P<.0001) scores, increased muscle fiber tenderness (P<.009) and overall tenderness (P<.005) ratings, and decreased the variation in palatability of steaks from young bull carcasses. Steaks from unstimulated (non-ES) young bulls with less than 6.5 mm fat thickness as well as steaks from “very masculine” carcasses were not as palatable as steaks from fatter, or less “masculine”, non-ES bull carcasses. Electrical stimulation had the greatest effect on the tenderness of steaks from young bulls with less than 6.5 mm fat thickness or “very masculine” bulls and essentially eliminated differences in tenderness of steaks from young bulls that differed in fat thickness or overall masculinity. Steaks from non-ES bulls in different overall masculinity groups did not differ (P>.05) in overall tenderness when fat thickness was held constant; therefore, for steaks from non-ES bulls, it seems that subcutaneous fat thickness is more important than masculinity as a predictor of differences in palatability.

Two-hundred and eighty beef carcasses were used to provide information on retail cut yields from beef carcasses varying widely in weight, fatness and muscling. In multiple regression equations, actual carcass measurements and commonly used subjective carcass evaluations usually accounted for over 80% of the variation of these yields. Adjusted fat thickness over the ribeye, percentage of kidney, pelvic and heart fat, and ribeye area, in that order, were the most important factors for predicting carcass yields of boneless, closely trimmed retail cuts. Carcass weight also contributed significantly (P<.05) in the equations in which it was used. These are the same four factors presently used in the official yield grade standards. On the average, the carcasses had higher yields than were predicted by the yield grades. A regression equation developed from this study and based on the same factors was only slightly more highly correlated with cutability than was the equation from which the present yield grades were derived. There also was little evidence that the equation from which the present yield grade equation was derived discriminated against certain types of carcasses more than the corresponding equation developed from this study. Therefore, there would be little advantage to revising the present USDA yield grade standards for the purpose of improving the cutability predictions of the present standards.

Feeder steers (n=471) were fed for 100, 130 or 160 days, then slaughtered, and carcass grade data were collected. A wholesale rib was removed from each carcass, vacuum packaged, and aged for 12 to 14 days, and steaks were obtained, Palatability of the steaks generally increased as marbling score increased; however, the differences in palatability associated with each successive increase in marbling score were not always directionally consistent, nor were they always statistically significant. Steaks from the highest grading (by thirds of grades) carcasses (high Choice and average Choice) were (P<.05) more juicy, more flavorful and more desirable in overall palatability than were steaks from the lowest grading (by thirds of grades) carcasses (low Good and high Standard); however, steaks from low Choice, high Good and average Good carcasses did not differ in ratings for juiciness, tenderness or overall palatability. When steaks from carcasses of different grades (by full grades) were compared, grade was not associated with differences in palatability. Increased time on feed was associated with increased carcass maturity, increased fat deposition, decreased (higher numerical) yield grade and increased percentage of carcasses grading Choice. Increased feeding time from 100 days to 160 days had a beneficial effect on flavor desirability but did not significantly affect juiciness, tenderness or overall palatability. These data suggest that knowledge of feeding history might be a useful adjunct to — or substitute for — USDA quality grade for predicting beef palatability.

Carcasses of 786 steers derived from crosses of Hereford or Angus cows bred to Hereford, Angus, Charolais, Limousin, Simmental, South Devon and Jersey sires were fabricated into closely trimmed, semi-boneless retail cuts to study relationships among independent variables in the U.S.D.A. yield grade equation in breed groups that differ in growth and fattening characteristics.Simple correlations indicate carcass weight was a good predictor of cutability within a breed group but a poor indicator over all breed groups. Longissimusmuscle area had the lowest predictive value of the four variables studied. It may be more useful in populations of similar weight than in those varying widely in weight. Fat thickness at the 12th rib was the most useful predictor of cutability and is about equally useful within or over all breed groups. Percentage of kidney and pelvic fat, though lower in predictive value than 12th rib fat thickness, was useful within or over breed groups. Partial regression coefficients computed within each breed group were relatively similar though there were significant differences in intercept values for the different breed groups. Use of a single prediction equation for all breed groups would rank animals well within a breed group but would on the average underestimate or overestimate animals of a breed group by .1% to over 1% relative to actual cutability.

A cutability prediction equation derived from data on 129 steer and 80 heifer carcasses and based on the factors included in the USDA beef carcass yield grade equation, underestimated the cutability of steer carcasses by .19% and overestimated the cutability of heifer carcasses by .31%. However, this difference was essentially eliminated by substituting “carcass percentage of external fat trim” for “adjusted thickness of fat over the rib eye” in that equation. While the steer and heifer carcasses had similar patterns of fat deposition on their various parts, at the mean predicted cutability of the steers and heifers combined, heifer carcasses had greater (P<.05) percentages of external fat trim in 9 of 10 carcass areas than did steers. That difference was greatest for the fat trim from the cod or udder, chuck and rump, and least for the inside and outside round. Except for the outside round and flank, sex did not have a differential effect on fat deposition at different levels of predicted cutability. Heifers varied more in the amount of fat on their various parts than did steers, and subjective evaluations of the fatness of the various areas of the steer carcasses almost always had higher simple correlations with the corresponding actual percentages of external fat trim than did the heifer carcasses. It appears that any subjective carcass evaluation procedure aimed at eliminating the external fat trim sex-bias between steer and heifer carcasses would have to include an arbitrary adjustment reflecting that, by comparison with steer carcasses, heifer carcasses will be fatter than indicated by their appearance.

Seventy-three sides of beef were trimmed, before shrouding, of varying amounts of external fat at different locations and their mate sides were not trimmed. Each side was evaluated for adjusted fat thickness over the rib eye in terms of preliminary yield grade (PYG) by eight persons experienced in making such evaluations. The mean total PYG error in evaluating the trimmed sides was .26; among evaluators, the error ranged from .22 to .31 PYG. The group mean PYG repeatability was lower for untrimmed than trimmed sides (.13 vs .20, respectively), but three evaluators had essentially the same PYG repeatability on trimmed and untrimmed sides. Evaluators almost always overestimated the effect of trimming on sides trimmed of fat only over the rib eye or on sides trimmed only on the primal cuts, while for sides trimmed of flank and(or) cod or udder fat, the effect of trimming usually was underestimated. If fat trimming were legitimated, USDA meat graders likely would need special instruction to properly evaluate the PYG of carcasses in which such trimming had substantially changed the relative amounts of fat present on the different parts.