Effect of growth path on carcass and meat-quality traits of Hereford steers finished on pasture or in feedlot

The objective of this study was to evaluate the effect of nutritional management during rearing and finishing phases on beef fatty acid composition, and carcass and beef quality traits of Hereford cattle. The study used 240 castrated male calves weaned at 8 months of age, and with an average weight of 170 ± 17 kg. After weaning, the experiment was divided in to three phases in a 4 × 2 factorial design: a 93-day winter period with four treatment groups (on pasture or in feedlot and at high or low feeding levels); a 196-day compensatory-growth phase on pasture; and a finishing phase either on pasture or in feedlot. Animals were slaughtered when each group attained a mean liveweight of 500 kg. The winter growth × finishing management interaction significantly affected hot carcass weight (P = 0.0029). There was no differences observed for feedlot-finished steers, but for pasture-finished steers, those pasture-reared had higher hot carcass weight (kg) than those feedlot-reared (low pasture 256.30 ± 1.60, high pasture 253.72 ± 1.60, low feedlot 249.85 ± 1.66, high feedlot 247.60 ± 1.62). Feedlot-finished steers showed higher (P < 0.05) mean values than pasture-finished steers for ribeye area (55.61 ± 0.69 cm2 vs 53.18 cm2), backfat thickness (8.62 ± 0.32 mm vs 6.21 mm), marbling score (237.97 ± 13.06 vs 171.70) and final pH (5.53 ± 0.02 vs 5.48). Additionally, feedlot-finished steers raised in feedlot during the winter-growth period displayed the heaviest hindquarter cuts. Meat from pasture-finished steers had lower (P < 0.05) shear-force values than from feedlot-finished cattle (2.95 ± 0.18 vs 3.66 ± 0.17 kg), and when reared on either high or low pasture during winter-growth, they showed the highest (P < 0.05) conjugated linoleic acid (cis-9, trans-11) and n-3 polyunsaturated fatty acid concentrations. In conclusion, growing and finishing cattle on pasture improved the carcass yield of retail cuts because of low fat concentration, and improved the nutritional and health value of the beef fatty acid profile.

Feedlot performance and carcass evaluation of heifers fed finishing diets as weanling calves or as yearlings

Twenty commercial Herefored, Angus and Hereford × Angus, weanling and yearling heifers from the same herd were compared for feedlot performance and certain carcass characteristics. Yearlings tended to gain weight more rapidly than did weanlings. Since the cattle were group-fed, no analyses of feed efficiency could be performed. Yearlings appeared, however, to require less feed per unit of gain. The cattle were slaughtered when live weight approached 443 kg. Weanlings were fatter; had more kidney, pelvic and heart fat; merited higher (less desirable) USDA yield grades; had more desirable USDA quality grades and higher dressing percentage (P<0·05) than did yearlings. Ribeye area was not different between treatments. Yearlings yielded a higher percentage of closely trimmed retail lean cuts than did weanlings (P < 0·05). Sensory panel scores were higher (more desirable) for weanlings than for yearlings for both ribeye and inside round steaks (P < 0·05), while no differences were identified for flavor, juiciness or overall palatability of steaks. Warner-Bratzler shear force data generally supported taste panel evaluations for tenderness. These data suggest that carcass composition is impacted by the way cattle are managed and refute the idea that cattle have the same body composition at a given weight regardless of age at slaughter or nutrient density of the diet during finishing.

Effects of backgrounding and finishing growth rates on P8 fat and intramuscular fat in Bos taurus steers

The present study investigates the effects of backgrounding and finishing growth rates of Bos taurus steers grown out on three post-weaning growth pathways, across 4 years (1995–1998) on fat deposition. Scanned P8 fat at backgrounding exit (SP8exit), scanned P8 fat before slaughter (SP8sla) and carcass intramuscular fat (IMF, %) were evaluated. Four equations to predict SP8sla and four equations to predict carcass IMF across years were developed. Three post-weaning growth pathways (GPs) generated by different nutritional treatments across years were used in the study. Growth pathways were created by backgrounding steers on pasture with no supplementation (GP1), pasture plus supplementary feeding formulated pellets (GP2) or pasture with access to a forage crop (GP3). The steers were then finished in a feedlot or on pasture to slaughter weights of 520 kg (Korean market specification) or 600 kg (Japanese market specification). Cubic smoothing splines were fitted to the liveweight of all animals from the start of backgrounding until slaughter. Backgrounding growth rates were interpolated off the GP curves and the mean average daily gain (ADG, kg/day) at Day 100 (D100, Days 100–91 before relocation to the finishing phase), and Day 150 (D150, Days 150–141 before relocation to the finishing phase) were calculated. Significant (P < 0.01) differences between SP8exit and backgrounding ADG (BADG) were detected in all years except GP2 v. GP3 in 1997. GP1 steers had the lowest BADG across all years, ranging from 0.39 to 0.88 kg/day. At backgrounding exit, the mean SP8exit for the different GPs was ranked, with GP1 < GP3 for all years, with significant (P < 0.01) differences among GP1, GP2 and GP3 in all years except 1996. At the end of finishing, the mean carcass IMF over all years and finish (pasture and feedlot) (P < 0.05) was 4.71% for GP1 v. 5.09% for GP3 for Korean market steers and the mean SP8sla (P < 0.01) was 14.59 mm for GP1 v. 16.04 mm for GP3 and the mean carcass IMF (P < 0.01) was 5.54% for GP1 v. 6.27% for GP3 for Japanese market steers. The residual correlation of the multivariate response variables, namely, D100, D150 and BADG v. SP8exit (n = 1054), SP8sla (n = 1049) and carcass IMF (n = 1002), indicated that the highest correlations, all significant (P < 0.01), were 0.33, 0.20 and 0.12 for BADG v. SP8exit, SP8sla and carcass IMF, respectively. The residual variances (mm2) of the four SP8sla equations were 6.14, 7.44, 8.72 and 10.73 for 1995, 1996, 1997 and 1998, respectively, and the residual variances (%2) for the four carcass IMF equations were 2.51, 2.26, 1.75 and 0.84, for 1995, 1996, 1997 and 1998, respectively.

Adiposity of calf- and yearling-fed Brangus steers raised to constant-age and constant-body weight endpoints

We tested the hypothesis that fatty acid biosynthesis and adipocyte diameter and volume would be greater in s.c. and i.m. adipose tissues of calf-fed steers than in yearling-fed steers at a constant BW, due to the greater time on feed for the calf-fed steers. Conversely, we predicted that the capacity for s.c. and i.m. preadipocytes to divide, as estimated by 3H-thymidine incorporation into DNA, would be greater in the less mature adipose tissues of calf-fed steers and in yearling-fed steers at 16 mo of age than in yearling-fed steers fed to 18 mo of age. Brangus steers were fed a corn-based finishing diet as calves (calf-fed; n = 9) or yearlings (n = 4) to 16 mo of age (CA yearling-fed); another group of yearlings (n = 5) was fed to a constant-BW end point of 530 kg (CW yearling-fed). Both groups of yearling-fed steers had free access to native pasture until 12 mo of age. At slaughter, the fifth to eighth thoracic rib section of the LM was removed, and fresh s.c. and i.m. adipose tissues were removed for in vitro incubations. There were no differences in the number of s.c. adipocytes/g or mean peak volumes of adipocytes across production groups (P > or = 0.14). However, s.c. adipose tissue of CA yearling-fed steers contained greater proportions of smaller adipocytes (<1,500 pL) than calffed or CW yearling-fed steers, and similar results were observed for i.m. adipose tissue. Acetate incorporation into total lipids was greater (P = 0.02) in s.c. adipose tissue of CA yearling-fed steers than in calf-fed or CW yearling-fed steers, and tended to be different (P = 0.10) across production groups in i.m. adipose tissue. The production system x cell fraction interaction was significant (P = 0.03) for s.c. adipose tissue DNA synthesis, which was greatest in adipocytes from CA yearling-fed steers, whereas there were no differences across production system in stromal vascular (SV) DNA synthesis. For i.m. adipose tissue, DNA synthesis was greatest in adipocytes and SV cells from CA yearling-fed calves, and was greater in SV cells than in adipocytes (both P = 0.01). Therefore, stage of adipose tissue development more strongly influenced fatty acid synthesis, adipocyte volume, and DNA synthesis than age at sampling, final BW, or time on the finishing diet.

Carcass traits and M. longissimus lumborum palatability attributes of calf- and yearling-finished steers

A 2-yr experiment was conducted to compare carcass characteristics and meat palatability attributes of steers ((3/4) British, (1/4) Continental) finished postweaning as calves or yearlings. Calves and yearlings of the same contemporary group were designated to a finishing system at weaning. Calves (n = 73) were finished in the feedlot (191 d) on a high-concentrate diet. Yearlings (n = 84) grazed crop residues after weaning, followed by spring and summer pasture grazing, and concluded with a short finishing period (91 d) in the feedlot. All steers were fed to a constant, fat thickness endpoint of 1 cm. The M. longissimus lumborum steaks from each production system were aged for 7, 14, or 21 d for Warner-Bratzler shear force determination and for 7 or 14 d for in-house sensory panel evaluation. Insoluble, percent soluble, and total collagen were determined. Yearlings produced heavier (P < 0.001) carcasses with larger (P < 0.001) LM areas and lower (P < 0.001) marbling scores and quality grades. Calves possessed greater amounts of total collagen (P < 0.001), with a significantly greater percentage of soluble collagen compared with yearlings (39.72 vs. 24.38%). Calves produced steaks with lower (P < 0.001) shear force values and greater (P < 0.001) sensory ratings for flavor. The USDA Choice steaks from the calves were more (P < 0.001) tender and more (P < 0.050) palatable than Choice steaks from yearlings, and USDA Select steaks from calves were rated more tender (P < 0.001), juicy (P = 0.012), and desirable (P < 0.001) than Select steaks from yearlings. As expected, increasing aging time from 7- to 14- to 21-d produced steaks with lower (P < 0.001) shear force values, regardless of the production system. Risk probabilities showed 1.24% of the steaks from calf-finished steers and 21.22% of steaks from yearling-finished steers to be tough. Sensory rating probabilities showed the steaks from the calves were most likely to be desirable for tenderness, whereas steaks from the yearlings were most likely to be undesirable for tenderness, juiciness, flavor, and overall acceptability. Thus, calf-finished steers produce carcasses superior in quality and palatability compared with those from yearling-finished steers. However, yearling-finished steers can produce tender beef with extended aging.