One hundred and twenty spring-born steers comprising 40 Friesians (FR), 40 Limousin x Friesians (LM), and 40 Blonde d'Aquitaine x Friesians (BL), were reared together from shortly after birth to slaughter at a mean age of 771 days. They were at pasture in summer and were housed and offered grass silage plus concentrates in winter. All were implanted with anabolic agents. During the finishing winter, there was a 3 (breed types) x 2 (3 or 6 kg concentrates per day) x 2 (94 or 181 day finishing period) factorial arrangement of treatments.Slaughter weights per day of age, carcass weights per day of age and carcass weights of FR, LM and BL were 846, 828 and 866 (s.e. 8-0) g, 464, 476 and 497 (s.e. 4-9) g and 358, 368 and 385 (s.e. 3-8) kg respectively. LM had lower carcass length, carcass depth, leg length and leg width values than FR or BL but when these measurements were expressed per kg carcass weight the values for LM and BL were similar. Both LM and BL had better carcass conformation than FR, and BL had a lower carcass fat score than either FR or LM between which there was no difference. FR, LM and BL had carcass lean, fat and higher-priced lean proportions of 634, 669 and 685 (s.e. 3-7), 185, 168 and 144 (s.e. 3-7) and 352, 361 and 361 (s.e. 1-4) g/kg respectively.Increasing the concentrate level from 3 to 6 kg per day increased side weight by 9-6 kg (P < 0-001). This consisted of 0-6 kg bone, 3-3 kg lean and 5-7 kg fat. Extending the finishing period from 94 to 181 days increased side weight by 30-3 kg (P < 0-001). This consisted of 2-6 kg bone, 12-0 kg lean and 15-7 kg fat. Allometric regression coefficients for side lean, bone and fat weights on side weight were not significantly affected by breed type or concentrate level. The coefficients for lean, bone and fat were 0-80 (s.e. 0-04), 0-58 (s.e. 0-05) and 2-27 (s.e. 0-16) respectively. The coefficients for weights of lean in the hind-shin, fore-shin, fillet and brisket on side lean weight were 0-8 or lower. The corresponding coefficients for silverside, inside round, knuckle, rump and strip-loin were between 0-8 and 1-0 while the flank, shoulder, neck, chuck, plate, fore-rib and cube-roll had coefficients in the range 1-0 to 1-5.

One hundred and sixty-two spring born steers comprising 54 Charolais × Friesian (CH), 54 Hereford × Friesian (HE) and 54 Friesians (FR) were reared together from shortly after birth until the end of their second grazing season at a mean age of 573 days. The animals were then blocked on weight within genotype, housed in a slatted shed and allocated to either a high (12·6 MJ metabolizable energy (ME) per kg) or a medium (10·4 MJ ME per kg) energy diet offered ad libitum until slaughter at one of three target carcass weights · light (260 kg (HE, FR and CH)), normal (300 kg (HE and FR) and 320 kg (CH)) or heavy (340 kg (HE and FR) and 380 kg (CH)) to give a 3 (breed type) · 2 (energy level) · 3 (slaughter weight) factorial arrangement during the finishing winter. The trial was repeated in 3 years consecutively.CH were significantly heavier than HE at all times up to 18 months of age when they were 43 kg heavier, at which stage they were also 24 kg heavier than FR. CH grew significantly faster at pasture than HE in both seasons and faster than FR in the second season. HE had the best daily gain in the finishing period.Overall slaughter weights per day of age, carcass weights per day of age and carcass weights of CH, HE and FR were 812, 771 and 761 (s.e. 9·2) g, 448, 418 and 405 (s.e. 4·8) g and 318. 299 and 298 (s.e. 2·2) kg, respectively. CH had significantly better killing-out proportions (lOg/kg) than HE which in turn were 10 g/kg better than FR. CH and FR had similar carcass length, carcass depth, leg length and leg widths and both were significantly larger than HE. CH had significantly larger longissimus dorsi areas than either HE or FR (80·9 v. 67·0 and 66·4 cm-); they also had significantly better conformation scores than HE which in turn were significantly better than FR.Increasing the energy level during the finishing period increased daily gain by proportionately 0·52 (1089 v. 684 g/day), reduced slaughter age by 51 days (711 v. 762 days) and significantly increased killing-out proportion (551 v. 534 g/kg) and conformation score (4·86 v. 4·64). Offal as a proportion of empty live weight tended to be higher for FR than for HE or CH, the exception being the hide, which was significantly lower for FR.

The carcass composition of Hereford x Friesian (HE), Friesian (FR) and Charolais x Friesian (CH) steers finished on diets of high (H) and medium (M) dietary metabolizable energy (ME) concentrations and slaughtered at low (L), normal (N) and heavy (W) carcass weights was examined in a 3 x 2 x 3 (no. = 9 per individual treatment) factorial experiment. A pre-finishing slaughter group of nine animals of each breed type was also included, giving a total 189 animals in 21 experimental groups. ME concentrations of the H and M diets which were offered ad libitum were 12-6 and 10-4 MJ/kg dry matter. Target carcass weights for L, N and W were 260, 300 and 340 kg for HE and FR and 260, 320 and 380 kg for CH.Carcass side weights (before tissue separation) of the HE, FR and CH pre-finishing slaughter groups were 90-8, 970 and 101-0 (s.e.d. 3-9) kg. Corresponding tissue proportions were 188, 199 and 200 (s.e.d. 4-3) g/kg bone, 663, 686 and 690 (s.e.d. 5-3) g/kg muscle and 135, 99 and 96 (s.e.d. 5-7) g/kg fat. Main effect side weights of the finished groups were 152-3, 151-4 and 162-2 (s.e.d. 1-4) kg for HE, FR and CH. 158-5 and 152-2 (s.e.d. 1-1) kg for H and M and 131-2, 155-2 and 179-6 (s.e.d. 1-4) kg for L, N and W, respectively. Tissue proportions in the same order were 146, 160 and 157 (s.e.d. 2-0), 149 and 159 (s.e.d. 1-6) and 163, 154 and 146 (s.e.d. 2-0) g/kg bone, 579, 601 and 635 (s.e.d. 5-5), 600 and 610 (s.e.d. 4-5) and 637, 599 and 574 (s.e.d. 5-5) g/kg muscle and 264, 228 and 195 (s.e.d. 6-4), 240 and 219 (s.e.d. 5-2) and 188, 235 and 264 (s.e.d. 6-4) g/kg fat. CH had more (P < 0-001) of their muscle in the pelvic limb and less (P < 0001) in the thorax than HE and FR. HE had more (P < 0-001) of their carcass fat in the subcutaneous depot and less (P < 0-001) in the intermuscular depot than FR and CH. The allometric regression coefficients for the main joint and tissue weights on side weight were l-0 for the thorax, ribs, flank and fat. The regression coefficients for the main muscles of the pelvic limb and loin and total thoracic limb muscle on total side muscle were l-0. Similarly the regression coefficients for the bones of the two limbs on total side bone were <10, while the coefficients for the loin, ribs and thorax bones were > 1 0 . It was calculated (for the H diet) that at a carcass weight of 300 kg, HE, FR and CH would have carcass tissue proportions of 576, 600 and 642 g/kg muscle and 261, 227 and 180 g/kg fat. The three breed types would have similar carcass fat contents at carcass weights of 264, 300 and 376 kg for HE, FR and CH, respectively.

One hundred and twenty spring-born steers comprised of 40 Friesians (FR), 40 Canadian Hereford × Friesians (HF) and 40 Simmental × Friesians (SM) were reared together from shortly after birth to slaughter after a mean period of 740 days. During the finishing winter there was a 3 (breed types) × 2 (3 and 6 kg supplementary concentrates per head daily with grass silage ad libitum) × 2 (222- and 225-day finishing periods) factorial arrangement of treatments. One side from each of 96 carcasses (eight per treatment) was completely separated into bone, muscle, intermuscular fat and subcutaneous fat and a 10th rib sample of m. longissimus was chemically analysed.Carcass weights per day of age and carcass weights were 404, 433 and 449 (s.e. 4·6) g and 301, 320 and 330 (s.e. 3·4) kg for FR, HF and SM, respectively. Corresponding proportions of carcass muscle were 602, 577 and 628 (s.e. 4·8) g/kg. FR and HF had similar proportions of their total muscle in the hindquarter, whereas SM had more of their muscle in the hindquarter. M. longissimus lipid concentrations for FR, HF and SM were 36, 39 and 26 (s.e. 1·96) g/kg. Increasing supplementary concentrate level from 3 to 6 kg/day increased side weight by 7 kg, of which proportionately 0·48 was fat. Extending the finishing period from 121 to 225 days increased side weight by 22 kg of which proportionately 0·45 was fat. Both the higher concentrate level and the longer finishing period reduced carcass muscle and bone proportions, and increased carcass fat proportion. Allometric regression coefficients for side muscle, bone and fat weights on side weight were 0·75, 0·51 and 2·13, respectively. It was calculated that FR, HF and SM would have similar carcass fat proportions at approximate carcass weights of 320, 290 and 380 kg, respectively.

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