The influence of sex-class, USDA yield grade and USDA quality grade on seam fat trim from the primals of beef carcasses

Beef carcasses (129 steers and 80 heifers) differing in weight, muscling, fatness and marbling score were selected to represent the full spectrum of USDA yield grades; one side was fabricated into boneless primal cuts. Primals were trimmed of all external fat and intermuscular (seam) fat and all components were weighed. Regression equations were developed to predict the percentage of seam fat on an external fat-free primal basis using USDA yield grade (YG), marbling score and a squared function of YG as the independent variables. YG (.77) and marbling score (.67) were highly correlated to seam fat. Heifers tended to have a higher predicted percentage of seam fat than did steers across all YG. Primals from USDA Choice carcasses had approximately 1.0 percentage point more predicted seam fat than did USDA Select primals at the same YG and sex-class. The YG 2.5 heifers had similar proportions of predicted seam fat from primals as YG 3.5 steers, but YG 3.5 heifers tended to have more seam fat than YG 4.5 steers. The same trend was noted between YG 4.5 heifers and YG 5.5 steers, indicating a sex-related deposition of seam fat in fed cattle.     

Influence of body condition score on carcass characteristics and subprimal yield from cull beef cows.

Mature beef cows (n = 83) were slaughtered to measure the influence of body condition score (BCS) on carcass characteristics and subprimal yields. All cows were weighed and assigned BCS, based on a 9-point scale, 24 h before slaughter. Cows were slaughtered, and, after a 48-h chilling period, quality and yield grade data were collected on the left side of each carcass. The right side was quartered, fabricated into primal cuts, and weighed. Each primal cut was further processed into boneless subprimal cuts, minor cuts, lean trim, fat, and bone. Cuts were progressively trimmed to 6.4 and 0 mm of external and visible seam fat. Weights were recorded at all stages of fabrication, and subprimal yields were calculated as a percentage of the chilled carcass weight. Live weight, carcass weight, dressing percentage, fat thickness, longissimus muscle area, muscle:bone ratio, and numerical yield grade increased linearly (P = .0001) and predicted cutability and actual muscle-to-fat ratio decreased linearly (P = .0001) as BCS increased from 2 to 8. Carcasses from BCS-8 cows had the most (P<.05) marbling. The percentage of carcasses grading U.S. Utility, or higher, was 16.7, 20.0, 63.6, 43.3, 73.3, 100.0, and 100.0% for cows assigned a BCS of 2, 3, 4, 5, 6, 7, and 8, respectively. At 6.4 mm of fat trim, carcasses from BCS-5 cows had higher (P<.05) shoulder clod yields than carcasses from cows having a BCS of 6, 7, and 8. Carcasses of BCS-2 cows had lower (P<.05) strip loin yields than carcasses from BCS-3, 4, 5, 6, and 7 cows. Top sirloin butt yields were higher (P<.05) for carcasses of BCS-2, 3, 4, and 5 cows than those of BCS-6, 7, or 8 cows. Carcasses from BCS-7 and 8 cows had lower (P<.05) tenderloin and inside round yields than carcasses of BCS-5, or less, cows. At both fat-trim levels, carcasses from BCS-5 cows had higher (P<.05) eye of round yields than cows assigned BCS of 2, 7, or 8. When subprimal cuts were trimmed to 6.4 mm of visible fat, carcasses from BCS-5 cows had higher (P<.05) total lean product yields than cows assigned a BCS of 2, 4, 7, and 8. Regardless of fat trim, total fat yields increased (P = .0001) and total bone yields decreased (P = .0001) linearly as BCS increased from 2 to 8. Although carcasses from BCS-5 and 6 cows had the highest yields of lean product, cattle producers and packers may benefit most by marketing and(or) purchasing BCS-6 cows because a higher percentage of their carcasses had quality characteristics deemed desirable for fabrication into boneless subprimal cuts.     

Effects of mass selection for increased weight at two ages on growth rate and carcass composition of Duroc-Landrace pigs

Duroc boars from a line previously selected over five generations for 200-d weight and those from a randomly selected control line were mated to Landrace sows either from a line previously selected for increased 70-d weight or from a randomly selected pedigree control line. From these matings, 900 pigs were farrowed to examine the effects of crossing lines of pigs mass selected for weight at two ages on growth rate, survival, and carcass composition. A greater (P less than .01) percentage of pigs farrowed survived birth from control-line sows (.974) than from select-line sows (.914). Of those pigs born alive, a greater (P less than .05) percentage of pigs out of control-line sows survived to 21 d (.893) than out of select-line sows (.829). Pigs sired by select-line boars weighed 2.1 kg heavier (P less than .05) at 70 d than pigs sired by control-line boars. Pigs out of select-line sows weighed .11 kg less (P less than .10) at birth and .3 kg less (P less than .10) at 21 d of age but grew .026 kg/d faster (P less than .10) from 70 d to slaughter, weighed 3.9 kg more at 165 d of age (P less than .05), and reached 100 kg 7.0 d sooner (P less than .05) than pigs out of control-line sows. Carcasses from barrows sired by select-line boars had .29 cm more (P less than .10) fat at the 10th-rib than carcasses from barrows sired by control-line boars. Marbling scores were .31 unit greater (P less than .05) and muscle color scores were .25 unit greater (P less than .10) for carcasses from pigs out of select-line sows than for carcasses from pigs out of control-line sows. Selection for increased 70-d weight decreased age at 100 kg without increasing fat deposition. However, survival rates up to 100 kg were reduced. Mass selection for 200-d weight effectively increased 70-d weight, but fat thickness at 100 kg also increased.     

Factors influencing intermuscular fat and other measures of beef chuck composition.

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).     

Genetic analyses of growth, real-time ultrasound, carcass, and pork quality traits in Duroc and Landrace pigs: I. Breed effects.

Knowledge of breed effects on carcass and pork quality traits is required to develop commercial crossbreeding programs that emphasize product quality. A 2 x 2 diallel mating system involving Landrace and Duroc pigs was used to estimate individual heterosis, direct breed effects and reciprocal cross differences for post-weaning growth, real-time ultrasound, carcass, and pork quality traits. Data from 5,649 pigs and 960 carcasses representing 65 and 49 sires, respectively, were analyzed assuming animal models. Duroc-sired pigs had 2.1 cm shorter carcasses with 7.3 mm less 10th rib backfat (BF), 4.4 cm2 larger longissimus muscle area (LMA), yielded 2.1 kg more estimated fat standardized lean (FSL), gained 16.5 g more estimated lean per day of age (LDOA), and had 1.0% less water (PWAT) and 1.9% more intramuscular fat (IMF) in the longissimus muscle than did Landrace-sired pigs (P less than .01), adjusted to an off-farm live weight of 111 kg. Reciprocal cross differences were detected for BF, LMA, FSL, LDOA and for subjective marbling, firmness, and muscling scores (P less than .01). Durocsired F1 barrows had 6.3 mm less BF and 5.9 cm2 larger LMA, yielded 3.2 kg more FSL, gained 22.3 g more LDOA, and had less marbling in the longissimus muscle and heavier ham muscling than reciprocal cross barrows. Heterosis estimates (P less than .05) were 27.6 g/d (3.2%) for ADG, -5.8 d (-3.6%) for off-test age, 2.7 cm (3.4%) for carcass length, 1.5 kg (7.2%) for FSL, 14.7 g (5.7%) for LDOA, -.07 (-3.6%) for muscle color, -.5% (-13.2%) for IMF, and .3% (.3%) for PWAT. Breed effects were not detected (P greater than .10) for muscle pH, cooking loss, shear value, and water-holding capacity or for eating quality traits. Reciprocal cross differences suggest an advantage in using the Duroc as a terminal sire, but improved carcass composition and higher intramuscular fat did not seem to affect eating quality traits.     

Effects of energy and protein supplementation of ammoniated tropical grass hay on the growth and carcass characteristics of cull cows

Laboratory, digestion and growth studies were used to evaluate energy and protein supplements for ammoniated (4% of the forage DM) stargrass (Cynodon nlemfuensis Vanderyst var. nlemfuensis) hay. Ammoniation increased (P less than .05) total N concentration (.7 to .9% vs 1.7 to 2.0%) and in vitro digestion of OM, NDF and ADF and reduced (P less than .05) NDF concentration of stargrass hay. Two digestion (3 x 3 Latin square, 250-kg steers) and two growth (400-kg Brahman crossbred cull cows, eight head per pasture, two pastures per treatment, November through February) trials evaluated citrus pulp or liquid cane molasses (Trial 1) and molasses or molasses plus cottonseed meal (Trial 2) supplementation of ammoniated hay. Supplementation with byproduct energy sources, citrus pulp or molasses (either alone or with cottonseed meal), improved (P less than .05) OM digestibility but reduced (P less than .05) NDF and ADF digestibilities. Apparent nutrient digestibilities were similar (P greater than .05) between diets supplemented with citrus pulp and molasses and between diets supplemented with molasses and molasses plus cottonseed meal. In Trial 1, ADG by cull cows was greater (P less than .05) for citrus pulp- (.71 kg) or molasses-(.68 kg) supplemented diets than for hay fed alone (.49 kg). In Trial ADG was greater (P less than .05) for cull cows fed ammoniated hay supplemented with molasses plus cottonseed meal (.85 kg) than for those supplemented with molasses only (.69 kg). Feeding cows over the winter increased their (P less than .05) carcass weight, marbling score, USDA quality grade and lipid percentage of the 9-10-11 rib section compared with cows slaughtered at the beginning of the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reduction of carcass fat in swine with dietary addition of dihydroxyacetone and pyruvate

Swine weighing 80 to 85 kg were fed a basal corn-soybean meal diet plus a mixture of dihydroxyacetone and pyruvate (3:1) (triose) or Polycose (control), a glucose polymer, as 3.85% of calories (4% of the diet). Twenty-four pigs were pair-fed the triose mixture or control diet for 28 d in litter-mate pairs of the same sex. Weight gain and feed consumption were recorded and carcasses were evaluated for fat and muscle accretion. The right rear leg and rear one-third of the right loin were skinned, deboned, ground and analyzed for protein, fat, moisture and ash content. Average backfat depth and backfat depth at the first, last and 10th rib were reduced by 12, 15, 14 and 12% (P less than .01), respectively, in triose-fed pigs. Loin eye area and untrimmed lean cuts were not altered by diet, but percentage trimmed lean cuts was higher (P less than .02) in triose-fed pigs (57.6 vs 55.3%). Leg and loin tissue samples from pigs fed the triose mixture had a lower (P less than .01) percentage of fat and a corresponding increased (P less than .01) percentage of protein. Organ weights and the blood biochemical profile were not altered by triose feeding. Liver function tests were not altered in animals consuming the trioses, except for an 18% decrease (P less than .05) in serum glutamic pyruvic transaminase. Ingestion of dihydroxyacetone and pyruvate will reduce body fat in limit-fed swine without reducing muscle protein deposition.     

Correlated responses in body composition based on selection for different indicator traits in mice

Correlated responses in whole-body composition were determined in 12-wk-old male mice from replicate lines selected for 12 generations for high (HF) or low (LF) epididymal fat pad weight as a percentage of body weight (EPID) and high (HL) or low (LL) hind carcass weight as a percentage of body weight. The HF and LF lines diverged (P less than .01) in body fat percentage (FAT) and subcutaneous depot fat by 93 and 71%, respectively, of the control line (RC) mean. EPID increased (P less than .01) proportionately more than FAT in the HF line; EPID decreased (P less than .01) proportionately less than FAT in LF. Protein, fat and water as a percentage of empty body weight showed negative correlated responses (P less than .01) due to selection for EPID, but lean body mass, body weight and body length had positive correlated responses (P less than .01). Correlated responses of fat-free protein and ash percentage were minor. Correlated responses in HL and LL were the mirror images of those in HF and LF, but they generally were of smaller magnitude. The results indicate that, although there are high positive genetic correlations between fat depots in mice, local control of lipogenesis and(or) lipolysis exists at different sites of fat deposition. Further, the lack of correlated responses in fat-free percentage of protein (and percentage of ash) suggests that additive genetic variances are low for these traits and(or) the genetic correlations of these traits with the selection criteria are low.     

GnRH in the infundibular stalk-median eminence is related to percentage body fat in carcasses of beef cows.

Mature Hereford cows (n = 28) were used to determine the effect of percentage body fat on secretion of LH and content of GnRH in the infundibular stalk-median eminence (ISME). Cows were fed to maintain, lose, or gain weight to achieve body condition scores (BCS; 1 = emaciated; 9 = obese) of 3 to 7. Then cows were fed to maintain weight and body condition. Before slaughter, estrus was synchronized using two injections of prostaglandin F2 alpha(PGF) 11 d apart. Five d after the second PGF injection, cows were given 100 micrograms of GnRH (im) and serum samples were obtained. LH was quantified using RIA. The anterior pituitary and ISME were obtained within 45 min of death. Anterior pituitary weight and LH concentration, total GnRH in the ISME, total carcass fat, and percentage carcass fat were determined. BCS of cows at the time of slaughter influenced percentage carcass fat (P less than .001), total GnRH in the ISME (P less than .02), and maximum LH after GnRH treatment (P less than .09), but did not influence pituitary weight or concentration of LH in the pituitary. Content of GnRH in the ISME averaged 76 +/- 12, 32 +/- 14, 27 +/- 13, and 24 +/- 13 ng for cows with BCS of 3, 5, 6, and 7, respectively. BCS was correlated (P less than .001) with percentage carcass fat (r = .94) and total fat in the carcass (r = .92). Total GnRH in the ISME was negatively correlated (P less than .005) with BCS (r = -.54), percentage carcass fat (r = -.55), and total carcass fat (r = -.49).(ABSTRACT TRUNCATED AT 250 WORDS)     

Muscle growth and satellite cell proliferative activity in obese (OB/OB) mice

Muscle growth of male obese (ob/ob) and lean mice at 2, 3, 5 and 8 wk were analyzed on the basis of weights of gastrocnemius, plantaris and soleus muscles from each hind leg. The carcasses (prepared by removing skin, viscera, head, feet and tail) were analyzed for fat content so that the effect of phenotype on the relationship between muscle weight and fat-free carcass weight could be assessed. For each age group the obese mice had less muscle relative to fat-free carcass weight than lean mice, with the difference being significant at 3 wk (P less than .05) and 8 wk (P less than .025). The proliferative activity of muscle satellite cells in 2- and 3-wk-old obese and lean mice was measured on isolated muscle fibers by autoradiography. Muscle fiber diameter and number of nuclei/unit length were unaffected by phenotype, but the proportion of muscle nuclei showing proliferative activity was lower (P less than .01) in obese than in lean mice at 2 wk (1.05 vs 1.93%, respectively) and 3 wk of age (.23 vs .59%, respectively). These results are consistent with the suggestion that muscle growth is limited by satellite-cell proliferative activity, although direct evidence for a cause and effect relationship is not provided.     

Characterization of muscles from boars, barrows, and gilts slaughtered at 100 or 110 kilograms: differences in fat, moisture, color, water-holding capacity, and collagen.

For characterization of ether-extractable fat content (EE), L*, a*, and b* color, and water-holding capacity (WHC), 12 muscles or muscle groups were dissected from 48 pork carcasses of boars, barrows, or gilts that were fed diets either at minimum (LO) or 1% above (HI) their protein requirements and slaughtered in two separate trials at 100 or 110 kg. In both trials across muscles, gilts and boars had lower (P < .05) EE than barrows. In the 110-kg trial, boars had lower (P < .001) EE than gilts. In the 100-kg trial, boars on LO diets had lower (P < .001) WHC than all other groups, and both boar groups had lower (P < .05) WHC than gilts. No differences (P > .05) in WHC were seen in the 110-kg trial. In the 100-kg trial, gilts had lower L* (P < .05) than boars and barrows, but in the 110-kg trial boars had lower L* (P < .05) than barrows and gilts. The lowest (P < .05) a* values were for boars in the 100-kg trial and for boars on LO diets in the 110-kg trial. In both trials, the serratus ventralis had more (P < .001) EE than all other muscles. In both trials, the semitendinosus had higher (P < .001) L* and the longissimus had lower (P < .01) a* and b* than all other muscles. The numerous differences observed among muscles may help identify optimal uses for the entire pork carcass.     

Characterization of biological types of cattle (Cycle VI): carcass, yield, and longissimus palatability traits

Carcass (n = 568) and longissimus thoracis palatability (n = 460) traits from F1 steers obtained from mating Hereford (H), Angus (A), and U.S. Meat Animal Research Center (MARC) III cows to H, A, Norwegian Red (NR), Swedish Red and White (RW), Friesian (F), or Wagyu (W) sires were compared. Data were adjusted to constant age (471 d), carcass weight (356 kg), fat thickness (1.0 cm), percentage of fat trim (24%), and marbling (Small35) end points. For Warner-Bratzler shear force and trained sensory panel traits, data were obtained on longissimus thoracis steaks stored at 2 degrees C for 14 d postmortem. The following comparisons were from the age-constant end point. Carcasses from H- and A-sired steers (377 and 374 kg, respectively) were the heaviest (P < 0.05) and carcasses from W-sired steers (334 kg) were the lightest (P < 0.05). A greater (P < 0.05) percentage of carcasses from A- and W-sired steers graded USDA Choice (88 and 85%, respectively) than carcasses from other sire breeds (52 to 71%). Adjusted fat thickness for carcasses from A-sired steers (1.3 cm) was highest (P < 0.05), followed by H-sired steers (1.1 cm) and W- and F-sired steers (0.9 cm); NR- and RW-sired steers (0.8 cm) had the lowest (P < 0.05) adjusted fat thickness. Longissimus thoracis area was not different (P > 0.05) among sire breeds (mean = 80.6 cm2). Carcass yield of boneless, totally trimmed retail product was least (P < 0.05) for A-sired steers (60.1%), intermediate for H-sired steers (61.5%), and similar (P > 0.05) for all other sire breeds (62.5 to 62.8%). Longissimus thoracis steaks from carcasses of A- (3.7 kg) and W-sired (3.7 kg) steers had lower (P < 0.05) shear force values than longissimus thoracis steaks from other sire breeds (4.1 to 4.2 kg). Trained sensory panel tenderness, juiciness, or beef flavor intensity ratings for longissimus thoracis steaks did not differ (P > 0.05) among the sire breeds. Sire breed comparisons were affected by adjusting data to other end points. Heritability estimates for various carcass, yield, and palatability traits ranged from very low (h2 = 0.06 for percentage of kidney, pelvic, and heart fat) to relatively high (h2 = 0.71 for percentage of retail product yield). Relative to the other sire breeds, W-sired steers had the highest percentage of USDA Choice, Yield grade 1 and 2 carcasses, but their carcasses were the lightest.     

Growth performance and carcass composition of lambs infused for 28 days with a growth hormone-releasing factor analogue.

A human growth hormone-releasing factor analogue, [DesNH2Tyr1,D-Ala2,Ala15]hGRF(1-29)NH2 (GRF-A), was infused s.c. into lambs for 28 d to determine its effects on growth performance and carcass composition. Twenty crossbred wethers weighing 47.0 +/- .5 kg were implanted with 7-d osmotic minipumps at weekly intervals. Minipumps contained either vehicle (dimethyl sulfoxide:H2O, 1:1) or GRF-A, released at a rate of 208 pmol (or .7 micrograms).h-1.kg-1. During the infusion period, plasma GH levels were increased (P less than .01) in GRF-A-treated wethers compared with control wethers (15.0 vs 9.3 ng/ml) and were higher on days that closely followed minipump implantation. Plasma IGF-I and hepatic IGF-I RNA concentrations were similar in lambs of both groups. Analogue treatment improved feed conversion (4.9 vs 5.8 kg dry matter/kg gain, P less than .05), increased average daily gain (.35 vs .30 kg, P = .05) and had no effect on feed intake, wool growth and body, carcass, selected organ and pituitary weights. Carcasses from GRF-A-infused lambs had less adjusted fat depth, a lower percentage of fat and a higher percentage of protein (P less than .05) than carcasses from control lambs. Magnitude of most effects of GRF-A on carcass measurements were correlated with the mean GH level that a lamb had during the infusion period. In conclusion, s.c. infusion of GRF-A improved feed utilization and altered carcass composition of feeder lambs in a relatively short period of time (28 d).     

Carcass traits, cut yields, and compositional end points in high-lean-yielding pork carcasses: effects of 10th rib backfat and loin eye area

Pork carcasses (n = 133) were used to investigate the influence of carcass fatness and muscling on composition and yields of pork primal and subprimal cuts fabricated to varying levels of s.c. fat. Carcasses were selected from commercial packing plants in the southeastern United States, using a 3 x 3 factorial arrangement with three levels of 10th rib backfat depth (< 2.03, 2.03 to 2.54, and > 2.54 cm) and three levels of loin eye area (LEA; < 35.5, 35.5 to 41.9, and > 41.9 cm2). Sides from the selected carcasses were shipped to the University of Georgia for carcass data collection by trained USDA-AMS and University of Georgia personnel and fabrication. Sides were fabricated to four lean cuts (picnic shoulder, Boston butt, loin, and ham) and the skinned belly. The four lean cuts were further fabricated into boneless cuts with s.c. fat trim levels of 0.64, 0.32, and 0 cm. The percentages of four lean cuts, boneless cuts (four lean cuts plus skinned, trimmed belly) at 0.64, 0.32, and 0 cm s.c. fat, fat-free lean, and total fat were calculated. Data were analyzed using a least squares fixed effects model, with the main effects of 10th rib backfat and LEA and their interaction. Fatness and muscling traits increased (P < 0.05) as 10th rib backfat and LEA category increased, respectively. However, fat depth measures were not affected greatly by LEA category, nor were muscling measures greatly affected by backfat category. The percentage yield of cuts decreased (P < 0.05) as backfat category increased. Cut yields from the picnic shoulder, Boston butt, and belly were not affected (P > 0.05) by LEA category, whereas the yield of boneless loin and ham increased (P < 0.05) as LEA category increased. Compositionally, the percentage of four lean cuts, boneless cuts at varying trim levels, and fat-free lean decreased incrementally (P < 0.05) as backfat depth increased, whereas parentage total fat and USDA grade increased (P < 0.05) as backfat depth increased. As LEA increased, percentage boneless cuts trimmed to 0.32 and 0 cm s.c. fat and fat-free lean increased and total fat decreased; however, the difference was only significant in the smallest LEA category. Collectively, these data show that decreased carcass fatness plays a greater role in increasing primal and subprimal cut yields and carcass composition than muscling even in lean, heavily muscled carcasses.     

Relationship between longissimus composition and the composition of other major muscles of the beef carcass

Left sides from 18 beef carcasses (9 steers and 9 heifers), selected to represent a wide range of marbling scores, were evaluated to determine the relationship between longissimus composition and the composition of other major muscles. The adductor (A), biceps femoris (BF), deep pectoral (DP) gluteal group (GL), infraspinatus (I), longissimus (L), psoas major (PM), rectus abdominis (RA), rectus femoris (RF), semimembranosus (SM), semitendinosus (ST), serratus ventralis (SV), spinalis (SP), supraspinatus (SU) and triceps brachii (TB) were removed, trimmed of external fat, weighed and ground for proximate analysis. Fat content of all muscles was related linearly (P less than .001) to L fat content (R2 values ranged from .67 to .84). The ST had the lowest mean fat content (4.4%) and SP had the highest mean percentage of fat (16.1%). The L ranged from 3.59% to 15.42% fat with a mean of 8.61%. Longissimus fat percentage can be used to predict the fat content of the other major muscles of the beef carcass.     

Physical and chemical components of the empty body during compensatory growth in beef steers

The composition of carcass and noncarcass tissue growth was quantified by serial slaughter of 26 Angus x Hereford crossbred steers (initial age and weight 289 +/- 4 d and 245 +/- 4 kg) during continuous growth (CON) or compensatory growth (CG) after a period of growth restriction (.4 kg/d) from 245 to 325 kg BW. All steers were fed a 70% concentrate diet at ad libitum or restricted levels. Homogenized samples of 9-10-11th rib and noncarcass tissues were analyzed for nitrogen, fat, ash, and moisture. Growth rate from 325 to 500 kg BW was 1.54 and 1.16 kg/d for CG and CON steers. The weight of gut fill in CG steers was 10.8 kg less (P less than .05) before realimentation and 8.8 kg more (P less than .10) at 500 kg BW than in CON steers. The allometric accretive rates for carcass chemical components relative to the empty body were not affected by treatment. However, the accretive rates for CG steers were greater (P less than .01) for noncarcass protein (.821 vs .265), noncarcass water (.861 vs .507), and empty-body protein (.835 vs. .601) than for CON steers. Final empty-body fat was lower (P less than .001; 24.2 vs 32.4%) and empty-body protein higher (P less than .001; 16.6 vs 14.8%) in CG steers than in CON steers. Consequently, net energy requirements for growth (NEg) were approximately 18% lower for CG steers. We conclude that reduced NEg requirements and changes in gut fill accounted for most of the compensatory growth response exhibited in these steers.     

Energy components of growth in Holstein steers fed formaldehyde- and formic acid-treated alfalfa or orchardgrass silages at equalized intakes of dry matter

Energy retention was compared in Holstein steers fed either alfalfa or orchardgrass silages for 164 d at either 65 or 90 g DM/kg.75 BW daily in a 2 x 2 factorial. Energy retention was estimated by slaughter-balance using an initial kill of eight steers at 216 kg and a final kill of eight steers per treatment at 326 kg. The ADG was not affected (P greater than .05) by silage, but steers fed alfalfa gained less (P less than .001) gut fill (they lost gut fill) and gained more (P less than .001) of the following than steers fed orchardgrass: empty body, 23%; fat, 50%; fat-free matter, 18%; protein, 16%; water, 17%; ash, 43%; gross energy, 31%; and carbon, 38%. With retained energy at 1.15 Mcal/d, retained energy was equally distributed between fat and protein. Increments of daily retained energy greater than 1.15 Mcal were deposited as 76% to fat and 24% to protein; this distribution was not affected by silage. The energy requirement for maintenance, with BW adjusted to equal gut fill, was not different (P greater than .05) at 130 kcal ME/kg.75 BW for steers fed alfalfa vs 125 for steers fed orchardgrass. Although not significant (P greater than .05), retained energy/ME intake above maintenance was 13% greater for steers fed alfalfa (.261) than for steers fed orchardgrass (.230), which supports the difference observed by calorimetry. The difference in dietary protein (25.6 vs 20.5%) did not contribute to the difference in energy retention because the differences in fat and protein retention could be explained totally by differences in daily energy deposition. The higher NDF of orchardgrass, or other fiber components, seems to be the most probable cause of its somewhat lower partial energetic efficiency relative to alfalfa.     

Influence of brahman-derivative breeds and Angus on carcass traits,physical composition,and palatability

Steers were generated from Angus (A), Beefmaster (BM), Brangus (BA), Gelbray (GB), and Simbrah (SB) sires mated to cows of their breed and to Brahman x Hereford F1 cows (except A) to characterize their carcass traits, composition, and palatability. The 290 steers (48 A, 48 BM, 36 BA, 31 GB, and 46 SB) were slaughtered at an equal fatness end point as determined by real-time ultrasound and visual evaluation. Angus steers had lighter (P < 0.01), more youthful (P < 0.01) carcasses with a higher (P < 0.05) quality grade, more (P < 0.01) fat thickness, and a larger (P < 0.01) longissimus area/100 kg than BM-, BA-, GB-, and SB-sired steers. Angus steers also had a lower (P < 0.01) specific gravity, a higher (P < 0.01) percentage fat and less (P < 0.05) lean in the 9th to 11th rib, and steaks aged for 10 d were more tender (P < 0.01) than steaks from Brahman-derivative sired steers. The BM- and BA-sired steers had lighter (P < 0.01), more youthful (P < 0.05) carcasses, and smaller (P < 0.01) longissimus area than GB- and SB-sired steers. The 9th to 11th rib section from the BM- and BA-sired steers had less lean and more bone (P < 0.01) than GB- and SB-sired steers. The BA-sired steers had more (P < 0.01) marbling and a higher (P < 0.05) quality grade than BM-sired steers. The SB-sired steers had heavier (P < 0.01) carcasses than the GB-sired steers. There were no differences in shear force for steaks aged for 3 d for any of the breed types, but with 10 d of aging, steaks from Angus steers were more tender, possibly indicating that steaks of Brahman-derivative breeds aged at a slower rate than those from Angus.     

Carcass, muscle and meat characteristics of lean and obese pigs

Six pigs obtained from a lean selected strain and six pigs obtained from an obese selected strain were slaughtered at about 110 kg live-animal weight. Carcasses were evaluated; hams were dissected into bone, skin, fat and lean, and loin samples were obtained for fiber type characteristics, percentage of fat and moisture, collagen analysis, sensory characteristics, textural properties and objective color analysis. Carcasses from lean pigs were longer, had less backfat and larger longissimus muscle cross-sectional areas than carcasses obtained from obese pigs. Hams from lean pigs had less fat, more bone and more lean than hams from carcasses of obese pigs. The percentages and cross-sectional areas of red and white muscle fibers of the longissimus muscle from lean and obese pigs were not different. However, lean pigs had intermediate fibers that were only 79% as large (P less than .10) as intermediate muscle fibers from obese pigs. Intermediate fibers represented only 7 and 10% of total fiber area, whereas white fibers represented 84 and 79% of total fiber area in longissimus muscle of lean and obese pigs, respectively. Overall, lean pigs tended to possess fewer fibers (-16%) per unit of area than obese pigs, indicating that total muscle fiber hypertrophy was partially responsible for the increased longissimus muscle area of the lean strain. Sensory properties of longissimus meat samples from lean and obese strains were not different. However, the shear force requirement of the longissimus samples from the lean strain were slightly, but significantly (P less than .10), higher than those from the obese strain. No differences were observed in meat color.     

Characterization of biological types of cattle (Cycle VII): Carcass, yield, and longissimus palatability traits

The objective of this experiment was to provide a current evaluation of the seven most prominent beef breeds in the United States and to determine the relative changes that have occurred in these breeds since they were evaluated with samples of sires born 25 to 30 yr earlier. Carcass (n = 649), yield (n = 569), and longissimus thoracis palatability (n = 569) traits from F(1) steers obtained from mating Hereford, Angus, and MARC III cows to Hereford (H), Angus (A), Red Angus (RA), Charolais (C), Limousin (L), Simmental (S), or Gelbvieh (G) sires were compared. Data were adjusted to constant age (445 d), carcass weight (363 kg), fat thickness (1.1 cm), fat trim percent (25%), and marbling (Small(35)) endpoints. For Warner-Bratzler shear force and trained sensory panel traits, data were obtained on LM from steaks stored at 2 degrees C for 14 d postmortem. The following comparisons were from the age-constant endpoint. Carcasses from L-, G-, and H-sired steers (361, 363, and 364 kg, respectively) were lighter (P < 0.05) than carcasses from steers from all other sire breeds. Adjusted fat thickness for carcasses from A-, RA-, and H-sired steers (1.5, 1.4, and 1.3 cm, respectively) was higher (P < 0.05) than for carcasses from steers from all other sire breeds (0.9 cm). Longissimus muscle areas were largest (P < 0.05) for carcasses from L-, C-, S-, and G-sired steers (89.9, 88.7, 87.6, and 86.5 cm(2), respectively) and smallest for carcasses from H- and RA-sired steers (79.5 and 78.4 cm(2)). A greater (P < 0.05) percentage of carcasses from RA- and A-sired steers graded USDA Choice (90 and 88%, respectively) than from carcasses from other sire breeds (57 to 66%). Carcass yield of boneless, totally trimmed retail product was least (P < 0.05) for RA- and A-sired steers (59.1 and 59.2%, respectively) and greatest (P < 0.05) for G, L-, C-, and S-sired steers (63.0 to 63.8%). Longissimus muscle from carcasses of A-sired steers (4.0 kg) had lower (P < 0.05) Warner-Bratzler shear force values than LM from carcasses of G- and C-sired steers (4.5 to 4.3 kg, respectively). Trained sensory panel tenderness and beef flavor intensity ratings for LM did not differ (P < 0.05) among the sire breeds. Continental European breeds (C, L, S, and G) were still leaner, more heavily muscled, and had higher-yielding carcasses than did British breeds (H, A, and RA), with less marbling than A or RA, although British breeds have caught up in growth rate.