No abstract

Carcass data for 1053 steers from the Meat and Livestock Commission's beef breed evaluation programme were used to examine the relative precision of alternative fatness assessments for predicting carcass lean percentage. The data were from four trials and comprised both dairy-bred and suckler-bred cattle by a wide range of sire breeds.A visual assessment of carcass subcutaneous fat content to the nearest percentage unit (SFJ was the single most precise predictor both overall (residual S.D. = 2-28) and within breed (residual S.D. = 2-05). Precision was improved by the addition in multiple regression of the percentage perinephric and retroperitoneal fat (KKCF) in carcass, a visual score of the degree of marbling in the m. longissimus and selected fat thickness measurements taken by calipers on cut surfaces (residual S.D. = 2-11 (overall) and 1-90 (within breed)).When the best overall equation was applied to the breed means, there was substantial bias (predicted -actual carcass lean percentage). Biases ranged from +2-5 (purebred Canadian Holstein and Luing) to -1-3 (Limousin crosses).Breeds differed significantly in carcass lean content when compared at equal levels of fatness measurements. The differences depended both on the precision with which the measurements predicted carcass lean content and the observed differences in carcass composition that existed before adjustments to equal fatness were made.The robustness of prediction equations was examined by applying them to independent sets of data (a total of 334 carcasses) from four other trials involving steers, heifers, cows and young bulls. Equations were stable for cattle of the same breed, sex and similar levels of fatness but important bias was found between more extreme types of cattle.

No abstract

Twenty buffalo steers were divided into four groups of five and were lot-fed for 86–287 days on nutritional regimes that varied from roughage to high-grain concentrate, and liveweight gains and carcass composition were determined. Mean daily liveweight gains were 0.74 kg (fed on three-quarters pellets + one-quarter hay), 0.67 kg (all pellets), 0.64 kg (three-quarters hay + one-quarter pellets) and 0.56 kg (all hay). Feeding regime had little effect on carcass composition. The proportions of muscle, bone, fat and connective tissue did not vary significantly among the four nutritional groups. The carcass composition of the buffalo steers did not differ greatly from that of a group of buffalo bulls previously dissected by the authors, the major difference being that the steers had significantly more fat (16.0%) than the bulls (10.6%). It was concluded that the carcass composition of the buffalo is relatively resistant to extremes of diet and to castration, and that the species does not show a propensity to fatten under 30 months of age.

The carcass yield of prescribed proportions of muscle and dissectible fat, described as 'carcass beef ', was studied in 49 steers of four breeds. Carcass beef consisting of 80% muscle, 20% fat and also of 75% muscle, 25% fat was predicted from fat thickness (FT), liveweight, carcass weight and dressing percentage. Carcass beef as a percentage of carcass weight was usefully estimated from FT (± 3%) but not from the other parameters. Carcass beef percentages and the corresponding FT measurements up to 15 mm were tabulated for the four breeds. There was no significant difference between the Herefords, Angus and Charolais X. Yield was less in the Friesians at a common FT, but a smaller FT was required to obtain a yield from carcasses of that breed. Carcass beef as a percentage of carcass weight, where the carcass beef composition is of specified proportions of muscle and dissectible fat, is proposed as a basis for the evaluation and marketing of carcasses.

Eleven Angus, 12 Friesian and 12 Hereford steers were used to investigate the degree of accuracy and usefulness of primal cut tissues in predicting side composition. The criteria used for evaluating the cuts were: (a) standard error of estimate of the equation, (b) homogeneity of 'b' values among breeds, (c) appreciable bone content in cut to allow the prediction of side bone, and (d) the absence of major difficulties in the replication and dissection of cuts. Simple and multiple regression analyses showed that the most accurate predictors of carcass composition, in descending order, with standard errors of estimate of muscle, fat and bone percentages respectively, were: hindquarter plus rib cut (0.37 %, 0.47 %, 0.30 %); hindquarter (0.73 %, 0.87%, 0.49%); loin plus rib cut (0.84%, 0.88%, 0.48%); rib cut (1.13%, 1.26%, 0.59%); loin (1.24%, 1.21 %, 0.72%). The most useful of four easily obtained carcass variables in improving the prediction accuracy of carcass components from multiple regression proved to be primal cut weight and fat thickness at the 12th rib, particularly the former. Both significantly reduced the standard errors of estimate of muscle, fat or bone in equations based on loin, rib cut and loin plus rib cut, but not in equations based on hindquarter plus rib cut and hindquarter. Kidney plus pelvic fat weight was of limited value, resulting only in a slight improvement in the prediction of side bone percentage using the equations based on bone percentage of the hindquarter. Carcass weight was of equal value to primal cut weight in improving the prediction accuracy of multiple regression. Five sets of part-carcass prediction equations are given, providing a choice of prediction accuracy, labour expenditure and cost for research workers whose requirements and resources may vary.

SUMMARYOne side of each of 51 carcasses of Hereford, Angus, Friesian and Charolais cross-bred steers was dissected and the weights of individual muscles and total carcass muscle were obtained. The percentage distribution of total carcass muscle weight in muscles and in. standard groups of muscles was determined. In addition, the percentage distribution of total carcass muscle weight in wholesale cuts was determined from the weights of whole and part muscles specified as comprising the respective cuts.Minor breed differences only were found in muscle weight distribution among muscles, groups of muscles and wholesale cuts. Similarity of muscle weight distribution in the different types of carcasses studied shows that carcass shape is not associated with differences in the distribution of muscle weight in wholesale cuts.

Comparisons of liveweight gain, carcass tissue weight gain and carcass composition were made between buffalo (Bubalus bubalis) steers and Angus, Friesian and Hereford steers, and among the three Bos taurus breeds following similar periods of lot-feeding. After a high-grain concentrate feeding regime for 182–205 days, mean daily liveweight gains were Herefords, 1.08 kg; Friesians, 0.88 kg; Angus, 0.72 kg; and buffaloes, 0.67 kg. At the commencement of lot-feeding, mean carcass composition was similar among Bos breeds whilst the buffaloes had higher proportions of muscle and bone and a lower proportion of fat. After lot-feeding there were slight changes only in the mean carcass composition of the buffaloes, whereas there were large changes in and among Bos breeds. An analysis of carcass weight gain showed that liveweight gain did not reflect differential tissue growth. The buffaloes, with a liveweight gain of 87 kg, gained 31.7 kg muscle and 9.3 kg fat. Corresponding gains in Bos breeds were Herefords, 141 kg liveweight for 31.3 kg muscle and 62.7 kg fat; Friesians, 108 kg liveweight for 3 2 8 kg muscle and 19.3 kg fat; and Angus, 98 kg liveweight for 12.5 kg muscle and 57.8 kg fat. The respective increases in weight of muscle and fat expressed as percentages of liveweight increase were buffaloes, 36.4 and 10.7; Herefords, 22.2 and 44.5; Friesians, 30.4 and 17.9; and Angus, 12.8 and 59.0. Regression equations for percentages of muscle, bone and fat on chilled carcass weight are given for the three Bos taurus breeds and the buffaloes.