Biomedical subjects

S D Shackelford

Publications and source records attributed to S D Shackelford.

At least 19 recordsLinked to original sources

PubMed1996

Effects of a beta-adrenergic agonist (L-644,969) and male sex condition on muscle growth and meat quality of callipyge lambs.

The objective of this study was to determine the effects of dietary administration of a beta-adrenergic agonist (BAA; L-644,969) and male sex condition (ram vs wether) on muscle growth and meat quality of Dorset x Romonov lambs believed to be heterozygous for the callipyge gene. At approximately 17 wk of age, lambs were blocked by weight within each sex condition and randomly assigned to BAA treatment group. The interaction of BAA and male sex condition was not significant for any of the traits measured. Rams had greater initial and final live weights, average daily gain, and hot carcass weight (P < .01). Rams did not differ (P > .05) from wethers with respect to any of the carcass traits, possibly because the wethers were so lean and heavily-muscled that there was little room for improvement. Kidney-pelvic fat weight was reduced 26% by BAA (P < .05). Knife separable lean weight and whole carcass proximate composition were not affected (P > .05) by BAA or male sex condition. Administration of BAA increased calpastatin activity at 20 d (1.1 vs 1.5 units/g), but not at 0 h (3.9 vs 4.8 units/g) postmortem, decreased myofibril fragmentation index (60.7 vs 44.9), and increased shear force (8.2 vs 10.9 kg) at 20 d postmortem (P < .05). These data suggest that muscle growth rates are near maximum in lambs expressing the callipyge gene, regardless of male sex condition or BAA treatment. Therefore, it seems that the callipyge gene exerts most, but not all, of its effect through intracellular events similar to those initiated by administering BAA.

Adrenergic beta-Agonists↗

PubMed1996

Sampling, cooking, and coring effects on Warner-Bratzler shear force values in beef.

A series of experiments was conducted to determine the effects of various factors on Warner-Bratzler shear force measurement of cooked beef. As the extent of thawing of frozen steaks before cooking for shear force evaluation increases (-2 vs 12 degrees C), shear force decreases (P < .05; 7.34 vs 5.99 kg). Location within the longissimus thoracis et lumborum from which steaks were obtained (caudal, medial, or cranial) did not affect (P > .05) shear force (5.21, 5.15, or 5.26 kg, respectively) or any sensory trait. Mean shear force of longissimus steaks cooked to either a constant temperature of 70 degrees C (6.97 kg) or for a constant time of 30 min (6.38 kg) was not different (P = .06), but shear force repeatability was higher for steaks cooked to constant temperature (.79 vs .53). Mean shear force (6.20 vs 6.33 kg) and shear force repeatability (.74 vs .68) of longissimus steaks cooked by either electric broiler or convection oven broiler, respectively, were not different (P > .05). Meat cores obtained perpendicular to the steak surface, from one location within the muscle, had lower (P < .05) mean shear force (3.41 vs 4.17 kg) and much less repeatable shear force (.12 vs .66) than cores obtained parallel to muscle fiber orientation. Use of more than five cores per animal did not significantly increase repeatability of mean shear force. Numerous factors must be carefully controlled to ensure measurement of shear force is as accurate and repeatable as possible.

Animals↗

PubMed1996

Effect of vitamin C concentration and co-injection with calcium chloride on beef retail display color.

The objectives of these experiments were to determine 1) the most effective vitamin C concentration to stabilize color of beef cuts during retail display and 2) the effect on color of incorporating vitamin C into a calcium chloride (CaCl2) injection solution. Top round cuts (semimembranosus and adductor) were injected with 5% by weight of a 0, .25, .5, 1, 2, or 4% sodium ascorbate solution (Exp. 1) or a 0, .5, 1, or 1.5% sodium ascorbate solution (Exp. 2). In Exp. 1, vitamin C resulted in more (P < .05) stable lean color during 9 degrees C display, and .5, 1, and 2% vitamin C were most (P < .05) effective. In Exp. 2, all concentrations of vitamin C maintained redder (P < .05) steaks after 3, 5, and 7 d of display than control steaks and had a lower (P < .05) percentage of surface discoloration after 5 and 7 d of display at 1 degree C. Experiment 3 used beef bottom round cuts (biceps femoris) to compare control, vitamin C- (1%), CaCl2-(200 mM) and vitamin C + CaCl2-treated steaks displayed at 1 degree C. Calcium chloride-treated steaks were more (P < .05) brown and had a higher (P < .05) percentage of surface discoloration on d 5 and 7 than control steaks, whereas steaks treated with vitamin C or vitamin C + CaCl2 were more (P < .05) red and had lower (P < .05) discoloration on d 5 and 7 than control steaks. Vitamin C can be injected into beef subprimals to enhance lean color stability and extend retail display life. Vitamin C also can be used in combination with CaCl2 to offset potential color deterioration, after 5 d of display, due to salt-induced oxidation.

Animals↗

PubMed1995

The effects of in utero exposure of lambs to a beta-adrenergic agonist on prenatal and postnatal muscle growth, carcass cutability, and meat tenderness.

The objectives of the present experiment were to examine the effects of in utero exposure to a beta-adrenergic agonist (L644,969) on prenatal and postnatal muscle growth and meat tenderness of lambs. Thirty twin-pregnant Composite IV (1/2 Finnsheep, 1/8 Dorset, 1/8 Rambouillet, 1/8 Targhee, 1/8 Suffolk) ewe lambs were used for this experiment. All ewes were fed an alfalfa hay-corn-based diet throughout gestation and lactation. From d 25 to 95 of gestation, the diet of one-half of the ewes contained 2 ppm of L644,969 on an as-fed basis. Treatment did not ( P > .05) affect lamb weights at any point in the growth cycle (birth to 43 kg). Heart weights of neonatal and market lambs were increased ( P < .05) by in utero exposure to L644,969. However, weights of lamb carcass components and weights of individual muscles were not affected by treatment (P > .05). Additionally, treatment did not alter the activities of any of the components of the calpain proteolytic system in neonatal or market lambs. Concomitantly, there was no effect of treatment on myofibril fragmentation index or Warner-Bratzler shear force. Moreover, there was no effect of treatment on muscle fiber type distributions, fiber sizes, or apparent fiber number. It seems that the lack of an effect of treatment on apparent fiber number would explain the lack of an effect on muscle weight. Thus, in utero exposure to L644,969 does not seem to have promise as a method for improving lamb carcass cutability. Other methods of improving the rate and composition of lamb carcass growth while maintaining acceptable meat tenderness must be developed.

Adrenergic beta-Agonists↗

PubMed1995

Effects of slaughter age on meat tenderness and USDA carcass maturity scores of beef females.

Two experiments were conducted to determine the effect of carcass maturity on meat palatability using concentrate-fed cattle of known history and to determine the relationship of chronological age to carcass maturity scores. Yearling heifers (n = 28) and 2-yr-old cows (n = 25) of similar breed groups were fed a high-energy-density diet for 90 d before slaughter. Longissimus muscle Instron peak load (Warner-Bratzler shear force) did not differ between age groups; but, fail elongation was higher for the 2-yr-old cows (P < .05). Overall tenderness ratings were lower for the 2-yr-old cows; however, the magnitude of the tenderness difference between age groups was small (.4 units on an 8-point scale). There was 10-fold more variation in tenderness within each age group than there was between age groups. Carcass maturity scores and chronological age were compared for heifers and cows (n = 249) ranging in age from 1.7 to 13.9 yr. Carcass maturity scores increased with increasing chronological age at a much faster rate than indicated by USDA. The following chronological age groups most accurately reflected the chronological age associated with each USDA carcass maturity class: A, 9 to 24 mo; B, 24 to 36 mo; C, 36 to 48 mo; D, 48 to 60 mo; E, > 60 mo. These results indicate that efforts to control variation in tenderness would be more effective if they targeted factors that have a greater effect on meat tenderness than does maturity class. Moreover, our results indicate that cows may grade lower at a given age than what USDA standards imply.

Aging↗

PubMed1995

Relationship between shear force and trained sensory panel tenderness ratings of 10 major muscles from Bos indicus and Bos taurus cattle.

The present experiments were conducted to determine 1) the relationship between shear force and overall tenderness of 10 major beef muscles, 2) the effect of Bos indicus inheritance on the tenderness of various beef muscles, 3) whether differences in tenderness between genotype are affected by method of cookery, and 4) the relationship between tenderness of the longissimus and tenderness of other muscles. To meet the first objective, shear force and trained sensory panel overall tenderness were determined for psoas major (PM), infraspinatus (IS), triceps brachii (TB), longissimus (LD), semitendinosus (ST), gluteus medius (GM), supraspinatus (SS), biceps femoris (BF), semimembranosus (SM), and quadriceps femoris (QF) steaks from grain-fed steer carcasses (n = 16). Shear force did not accurately reflect differences among muscles in overall tenderness. To accomplish the remaining objectives, muscles were removed from grain-fed Bos taurus x Bos taurus (n = 31) and Bos indicus x Bos taurus (n = 18) steer carcasses and aged until 14 d postmortem. Shear force of LD, TB, SS, BF, and QF steaks and QF, BF, TB, and LD roasts was higher (P < .05) for progeny of Bos indicus sires than for progeny of Bos taurus sires. Shear force differences among genotypes were reduced slightly by roasting. Shear force of LD was not highly related to shear force of other muscles. Thus, systems that accurately predict the tenderness of LD of a carcass will likely do little to predict the tenderness of other muscles.

Animals↗

PubMed1995

A muscle hypertrophy condition in lamb (callipyge): characterization of effects on muscle growth and meat quality traits.

The present experiment was conducted to determine the effect of the callipyge phenotype on traits affecting muscle growth and meat tenderness. Dorset wethers (N = 40) that were either carriers or non-carriers were fed grain and slaughtered at 169 d of age. Callipyge phenotype did not affect (P > .05) slaughter weight, hot carcass weight, or weights of the heart, spleen, viscera, kidney-pelvic fat, head, and pelt; however, callipyge lambs had a higher dressing percentage and lighter lungs, liver, and kidneys (P < .01). Callipyge lambs had reduced fat thickness and marbling score and higher leg scores and longissimus area (34%). Adductor (30%), biceps femoris (42%), gluteus group (31%), longissimus (32%), psoas group (20%), quadriceps femoris (18%), semimembranosus (38%), and semitendinosus (26%) weights were higher in the callipyge phenotype (P < .01); however, phenotype did not affect (P > .05) weights of infraspinatus or supraspinatus. Longissimus pH and temperature declines were not affected (P > .05) by phenotype. Longissimus myofibril fragmentation index was lower at 1 (27%), 7 (35%), and 21 (37%) d postmortem and Warner-Bratzler shear force was higher at 1, 7, and 21 d postmortem in the callipyge phenotype (P < .01). Shear force values of callipyge lambs at 21 d postmortem tended to be greater (P = .12) than shear force values of non-carriers at 1 d postmortem . Activities of calpastatin (83%) and m-calpain (45%) were higher in the callipyge (P < .01); however mu-calpain activity was not affected (P > .05). Longissimus and semitendinosus RNA concentration, DNA content, RNA content, protein content, and the RNA:DNA ratio were higher (P < .05), but DNA concentration, protein concentration, and protein:DNA were not affected in the callipyge phenotype. The higher calpastatin activity associated with callipyge suggests that protein degradation may be reduced in the live animal. Additionally, the increased muscle DNA content associated with the callipyge phenotype suggests an increase in satellite cell proliferation, and results in an increased capacity of skeletal muscle to accumulate and maintain myofibrillar protein. These results suggests that both reduced rate of protein degradation and higher capacity for protein synthesis are consequences of the callipyge condition.

Actinin↗

PubMed1995

Predicting beef carcass cutability.

Analyses were conducted to develop and test the efficacy of beef carcass cutability prediction equations. Data from 1,602 calf-fed steer carcasses (Germplasm Utilization Project; GPU) were used to develop the equations and an additional 1,160 calf-fed steer carcasses (Germplasm Evaluation Project; GPE) were used to validate the equations. In both experimental groups, USDA yield grade ranged from < 1 to > 5 and the SD of yield grade was > .8 indicating a relatively large amount of variation in carcass cutability. Models were developed to predict boneless, totally trimmed retail product yield (RPYD), fat trim yield (FATYD), and bone yield (BONEYD) using 1) carcass traits, 2) carcass traits and wholesale rib dissection traits, 3) carcass traits and 9-10-11 rib dissection traits, and 4) carcass traits and 9-10-11 rib dissection and chemical traits. For each dependent variable, the best single predictor was a wholesale rib dissection trait, and the best higher order model contained at least one wholesale rib dissection trait. Equations developed explained 87, 88, and 77% of the variation in RPYD, FATYD, and BONEYD, respectively. When validated against GPE carcasses, models developed from GPU carcasses explained 74, 78, and 69% of the phenotypic variation and 96, 94, and 84% of the genetic variation in RPYD, FATYD, and BONEYD, respectively. Prediction of carcass cutability using carcass and wholesale rib dissection traits should allow for rapid, precise, and cost-effective assessment of variation in cutability.

Animals↗

PubMed1994

Effect of biological type of cattle on the incidence of the dark, firm, and dry condition in the longissimus muscle.

The objectives of this experiment were to characterize longissimus muscle color, texture, and firmness for beef carcasses of diverse biological types and to determine the genetic parameters of lean color, texture, and firmness. The carcasses (n = 3,641) used in this experiment were from steers produced by mating Angus, Brahman, Braunvieh, Charolais, Chianina, Galloway, Gelbvieh, Hereford, Jersey, Limousin, Longhorn, Maine Anjou, Nellore, Piedmontese, Pinzgauer, Red Poll, Sahiwal, Salers, Shorthorn, Simmental, South Devon, and Tarentaise sires to Hereford and Angus dams. Steers were fed a corn-corn silage diet from weaning until slaughter at 356 to 575 d of age. Steers were slaughtered at commercial packing plants and longissimus muscle color, texture, and firmness were scored by trained carcass evaluators. Sire line least squares means for lean color, texture, and firmness ranged approximately one unit on a 7-point scale. Chianina crosses had darker-colored lean than all breed groups except Tarentaise and Simmental crosses (P < .05). Moreover, a higher percentage (P < .05) of Chianina crosses than of all other breed groups had unacceptably dark-colored ("dark red" or darker) lean. Bos indicus sire lines were not different from Bos taurus sire lines in frequency of carcasses with unacceptably dark-colored lean. However, Bos indicus crosses were more likely to be scored "very light cherry-red." Lean color and texture were lowly heritable, whereas lean firmness was moderately heritable. Thus, this experiment demonstrated that there is genetic variation in the incidence of the DFD condition; however, genetic variation was small relative to environmental variation.

Analysis of Variance↗

PubMed1994

Heritabilities and phenotypic and genetic correlations for bovine postrigor calpastatin activity, intramuscular fat content, Warner-Bratzler shear force, retail product yield, and growth rate.

To estimate the heritability (h2) of postrigor calpastatin activity (CA), 555 steers were reared and processed conventionally. Breed-types included purebreds (Angus [A], Braunvieh [B], Charolais [C], Gelbvieh [G], Hereford [H], Limousin [L], Pinzgauer [P], Red Poll [RP], and Simmental [S]), composite populations (MARC I [1/4 C, 1/4 B, 1/4 L, 1/8 H, 1/8 A], MARC II [1/4 S, 1/4 G, 1/4 H, 1/4 A], and MARC III [1/4 RP, 1/4 H, 1/4 P, 1/4 A]), and F1 crosses (H, A, C, G, P, Shorthorn, Galloway, Longhorn, Nellore, Piedmontese, or Salers x H or A). Steers were serially slaughtered on an age-constant (across breed groups) basis. Heritability estimates for CA, i.m. fat content (IMF), Warner-Bratzler shear (WBS) force, retail product yield (RPY), and ADG were .65 +/- .19, .93 +/- .02, .53 +/- .15, .45 +/- .18, and .32 +/- .26, respectively. The genetic correlations (rg) of CA with WBS, RPY, and ADG were .50 +/- .22, .44 +/- .25, and -.52 +/- .37, respectively. The rg of IMF with WBS, RPY, and ADG were -.57 +/- .16, -.63 +/- .15, and -.04 +/- .11, respectively. These h2 and rg estimates indicate that it should be possible to select for improvements in CA, IMF, and WBS. However, selection against CA may be a more suitable approach for improving meat tenderness than selection for increased IMF because the level of genetic antagonism between CA and RPY was not as great as that between IMF and RPY.

Adipose Tissue↗

PubMed1994

The efficacy of adding a minimum adjusted fat thickness requirement to the USDA beef quality grading standards for select grade beef.

The present analysis was conducted to test the efficacy of adding a minimum 5-mm adjusted s.c. fat thickness requirement to the present USDA beef quality grading standards for the Select grade. Carcass grade data and longissimus thoracis Warner-Bratzler shear force and trained sensory panel ratings were analyzed for calf-fed steers (n = 1,602). The experimental group (nine breeds and three composite populations finished on medium- and high-energy diets) contained a large amount of variation in yield grade, marbling score, Warner-Bratzler shear force, and sensory panel overall tenderness ratings (CV = 30.8, 17.9, 25.0, and 14.0%, respectively). All but one of the carcasses were of A maturity and 37% of the carcasses had < 5 mm adjusted fat thickness. Among carcasses with a "slight" amount of marbling, WBS values were higher (5.58 vs 5.32 kg; P < .01) and overall tenderness (4.82 vs 4.99; P < .01) was lower for carcasses with < 5 mm s.c. fat thickness than for those with > or = 5 mm s.c. fat thickness. However, the magnitude of those differences was so small that the current and proposed Select grades did not differ with respect to shear force (5.45 vs 5.32 kg), overall tenderness (4.90 vs 4.99), juiciness (5.09 vs 5.12), beef flavor intensity (4.86 vs 4.86), or the percentage of samples rated "slightly tender" or higher for overall tenderness (48.7 vs 52.0). Thus, it seems that the addition of a minimum fat thickness requirement to the standards for the Select grade would not improve the tenderness of Select grade longissimus thoracis steaks.

Adipose Tissue↗

PubMed1992

Retail cut yields of Rambouillet wether lambs fed the beta-adrenergic agonist L644,969.

Twenty Rambouillet wether lambs were given ad libitum access to a diet with (BAA, n = 10) or without (control, n = 10) 1 ppm of the beta-adrenergic agonist L644,969. Lambs were fed to a constant slaughter weight end point of 54.5 kg. Carcasses were fabricated to yield bone-in and boneless cuts that were trimmed progressively to 1.27, .64, .32, and .00 cm of s.c. fat remaining. Addition of BAA did not affect growth traits. Actual and adjusted fat thickness, body wall thickness, and percentage of kidney-pelvic fat did not differ between control and BAA lambs. However, BAA increased longissimus muscle area, longissimus muscle depth, and leg score while decreasing USDA yield grade. The BAA increased carcass conformation scores and decreased flank lean color scores. No other carcass quality measurements were affected by BAA. Addition of BAA did not affect overall carcass yields of bone-in retail cuts. However, BAA increased overall carcass yields of boneless retail cuts regardless of fat trim level. The BAA increased bone-in leg yield. Yield of boneless sirloin, bone-in loin and boneless loin were not affected by BAA. For these cuts, the percentage change from the control was highly dependent on fat trim level. There was no difference in short-cut, shank-off, semiboneless leg yield between control and BAA. Addition of BAA did not affect yield of bone-in rack regardless of fat trim level. However, BAA greatly increased yield of boneless ribeye. The BAA did not affect yield of bone-in or boneless shoulder.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗

PubMed1992

Effect of hot-fat trimming on factors associated with the subprimal yield of beef carcasses.

Thirty-two crossbred cattle (steers = 17; heifers = 15) exhibiting an ultrasound fat thickness at the 12 to 13th rib region of at least 10 mm were selected from a slaughter shift at a commercial packing plant. After splitting, alternating sides of each carcass were trimmed of 1) subcutaneous fat in excess of 6.4 mm; 2) all kidney, pelvic, and heart fat; and 3) all cod or udder fat and fat in the flank region. Both sides of each carcass were fabricated into subprimals (final trim level of 6.4 mm) according to normal industry procedures. Effect of hot-fat trimming, yield grade (3, 4, and 5), and gender on hot-fat trim, fabrication fat trim, major subprimal, and total subprimal yield of untrimmed and trimmed carcasses were determined. Higher numerical yield grade (YG) corresponded with higher (P less than .05) percentages of hot-fat trim. Hot-fat trimming increased (P less than .05) the difference in fabrication fat trim between steers and heifers and between YG 3 and YG 5. Steers and heifers differed (P less than .05) in percentage of major subprimals and total subprimals when processed conventionally, whereas hot-fat trimming eliminated this difference (P less than .05). Untrimmed YG 3 carcasses had 3.1 and 5.0% higher major subprimal yield (P less than .05) than untrimmed YG 4 and YG 5 carcasses, respectively, whereas hot-fat trimming reduced this difference to 2.5% for YG 4 and to 3.7% for YG 5.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗

PubMed1992

Lean color characteristics of bullock and steer beef.

Twelve young bulls and 12 steers were slaughtered and the carcasses were fabricated at 48 h postmortem. Top rounds, bottom rounds, and rib eyes were vacuum-packaged and stored at 0 degrees C until 21 d postmortem. After subprimal storage, steaks were removed from each cut and displayed under simulated retail conditions for 3 d. Consumer panelists (n = 110) showed little difference in buying preference for top round, bottom round, and rib eye steaks from steers vs bullocks. Also, consumer panelists could not detect color differences between steaks from steers and bullocks. Experienced panelists (n = 6) detected brighter (P less than .05) muscle color for top round and rib eye steaks from steers but detected no difference in muscle color of bottom round steaks from bullocks and steers. Generally, overall desirability scores favored steaks from steer carcasses. This was particularly true of rib eye steaks. Sex-class of carcass did not affect aerobic plate counts of top round, bottom round, or rib eye steaks either before or after 3 d of retail display. Muscle pH was lower for top round and rib eye steaks from steer carcasses; however, the magnitude of this difference was not large enough to affect retail display stability. Muscle pH of bottom round steaks was not affected by sex-class. Although experienced panelists could detect differences in visual appearance of beef retail cuts from steers and bullocks, consumer panelists did not show a clear purchase preference for steer vs bullock beef. These data suggest that beef retail cuts from bullocks are acceptable in visual appearance.

Animals↗

PubMed1991

An evaluation of tenderness of the longissimus muscle of Angus by Hereford versus Brahman crossbred heifers.

Postmortem aging of carcasses obtained from Angus-Hereford (n = 8) and 5/8 Brahman crossbred (n = 8) heifers was investigated to determine the cause of variation in meat tenderness. Raw longissimus muscle (LM) myofibril fragmentation index was lower and cooked LM Warner-Bratzler shear force was greater for the 5/8 Brahman crossbreds (P less than .05). The activities of calcium-dependent protease (CDP) -I and -II were not affected (P greater than .05) by breed; however, CDP inhibitor activity was higher (P less than .05) in the 5/8 Brahman carcasses. The activities of cathepsins B and B + L were not affected by breed or postmortem storage time (0, 1, 3, 7 or 14 d). Hereford-Angus carcasses were fatter opposite the 12th rib and had higher USDA yield grades and marbling scores (P less than .05). Hereford-Angus crossbreds had less dark, coarse band formation around the exterior of the LM and lighter, finer-textured lean (P less than .05). Cooking loss (%) and cooking rate (g/min) were not affected by breed or postmortem aging (P greater than .05). The increased toughness in the 5/8 Brahman carcasses may be due to increased CDP inhibitor activity.

Animals↗

PubMed1991

Effect of the beta-adrenergic agonist L644,969 on muscle growth, endogenous proteinase activities, and postmortem proteolysis in wether lambs.

To examine the effect of a beta-adrenergic agonist (BAA) on muscle growth, proteinase activities, and postmortem proteolysis, 16 wether lambs were randomly assigned to receive 0 or 4 ppm of L644,969 in a completely mixed high-concentrate diet for 6 wk. Weight of the biceps femoris was 18.6% heavier in treated lambs. At 0 h after slaughter, treated lambs had higher cathepsin B (35.6%), cathepsins B + L (19.1%), calpastatin (62.8%), and m-calpain (24.6%) than control lambs, but both groups had similar mu-calpain activities. In both longissimus and biceps femoris muscles, treated lambs had higher protein and RNA and lower DNA concentrations. However, total DNA was not affected, indicating that the increase in muscle mass was probably due to muscle hypertrophy rather than to hyperplasia. The pattern of postmortem proteolysis was significantly altered by BAA feeding. In treated lambs, postmortem storage had no effect on the myofibril fragmentation index and degradation of desmin and troponin-T. These results indicate that the ability of the muscle to undergo postmortem proteolysis has been dramatically reduced with BAA feeding. Similar proteolytic systems are thought to be involved in antemortem and postmortem degradation of myofibrillar proteins, so BAA-mediated protein accretion is probably due, at least in part, to reduced protein degradation. To examine whether protein synthesis was altered with BAA feeding, the level of skeletal muscle alpha-actin mRNA was quantified. Longissimus muscle alpha-actin mRNA abundance was 30% greater in BAA-fed lambs. Collectively, these results indicate that dietary administration of BAA increases muscle mass through hypertrophy and that the increase in muscle protein accretion is due to reduced degradation and possibly to increased synthesis of muscle proteins.

Actins↗

PubMed1991

Effect of calcium chloride infusion on the tenderness of lambs fed a beta-adrenergic agonist.

The objective of this study was to examine the effectiveness of CaCl2 infusion in overcoming the toughness of meat associated with dietary administration of a beta- adrenergic agonist (BAA) to lambs. Thirty-two crossbred (1/2 Finnsheep X 1/4 Dorset X 1/4 Rambouillet) wether lambs were randomly assigned to receive 0 or 4 ppm BAA (L644,969; Merck, Sharpe and Dohme Research Laboratories) in a completely mixed, high-concentrate diet for 6 wk. Animals were slaughtered in two groups of 16. At each slaughter time half of each group (0 or 4 ppm BAA) was randomly assigned to CaCl2 infusion. Feeding the BAA decreased (P less than .05) fat thickness, kidney-pelvic fat, yield grade, and marbling and increased (P less than .05) dressing percentage, lean firmness, leg score, and biceps femoris weight. Weight of biceps femoris was 32.8% greater in BAA-fed lambs. Treated, but not infused, lambs were significantly less tender than control lambs after 1, 7, and 14 d of postmortem storage. At 24 h postmortem, BAA-fed lambs had higher (P less than .05) cathepsin B, calcium-dependent protease-II (CDP-II), and CDP inhibitor activities. Calcium chloride infusion increased marbling, decreased lean firmness, increased lean color score, and increased dressing percentage (P less than .05). Infusion of carcasses with CaCl2 decreased (P less than .05) shear force at all postmortem times. Infusion of carcasses with CaCl2 had no effect on cathepsins B and B + L activities, but it had a significant effect on CDP-I, CDP-II, and CDP inhibitor activities.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗

PubMed1991

National beef tenderness survey.

To determine the average tenderness and sensory ratings of beef subprimal cuts sold in retail cases across the United States, retail cuts were purchased through typical retail outlets in 14 metropolitan cities and transported to Texas A&M University for sensory and Warner-Bratzler shear analysis. The overall mean shear force for all cuts was 3.65 kg, and the mean shear force values for chuck, rib, loin, and round cuts were 3.72, 3.36, 3.17, and 4.31 kg, respectively. No difference (P greater than .05) in tenderness was detected among the cuts from the rib. Mean palatability ratings and shear force values of top loin steaks were similar to those of rib cuts. Top sirloin steaks were tougher (P less than .05) and received the lowest sensory ratings compared with other loin cuts. Approximately two to three times as many round and chuck steaks had shear force values in excess of 4.6 kg compared with their roast counterparts. In all cases, roasts tended to be more tender than steaks from the same subprimal source. USDA Choice chuck retail cuts, compared to Select and No-roll chuck cuts, had approximately 10% fewer cuts with shear force values in excess of 4.0 kg. More work is needed to improve meat tenderness, primarily for retail cuts from the round and chuck primals. Future research must investigate the interaction of antemortem and postmortem factors associated with variation in beef tenderness.

Animals↗