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M Koohmaraie

Publications and source records attributed to M Koohmaraie.

At least 19 recordsLinked to original sources
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↗
PubMed1995

Is Z-disk degradation responsible for postmortem tenderization?

A number of studies have suggested that Z-disk degradation is a major factor contributing to postmortem tenderization. These conclusions seem to have been based largely on experimental findings showing that the calpain system has a major role in postmortem tenderization, and that when incubated with myofibrils or muscle strips, purified calpain removes Z-disks. Approximately 65 to 80% of all postmortem tenderization occurs during the first 3 or 4 d postmortem, however, and there is little or no ultrastructurally detectable Z-disk degradation during this period. Electron microscope studies described in this paper show that, during the first 3 or 4 d of postmortem storage at 4 degrees C, both costameres and N2 lines are degraded. Costameres link myofibrils to the sarcolemma, and N2 lines have been reported to be areas where titin and nebulin filaments, which form a cytoskeletal network linking thick and thin filaments, respectively, to the Z-disk, coalesce. Filamentous structures linking adjacent myofibrils laterally at the level of each Z-disk are also degraded during the first 3 or 4 d of postmortem storage at 4 degrees C, resulting in gaps between myofibrils in postmortem muscle. Degradation of these structures would have important effects on tenderness. The proteins constituting these structures, nebulin and titin (N2 lines); vinculin, desmin, and dystrophin (three of the six to eight proteins constituting costameres); and desmin (filaments linking adjacent myofibrils) are all excellent substrates for the calpains, and nebulin, titin, vinculin, and desmin are largely degraded within 3 d postmortem in semimembranosus muscle. Electron micrographs of myofibrils used in the myofibril fragmentation index assay show that these myofibrils, which have been assumed to be broken at their Z-disks, in fact have intact Z-disks and are broken in their I-bands.

Animals↗
PubMed1995

Postmortem injection of calcium chloride effects on beef quality traits.

Twenty-two Bos indicus type steers were commercially slaughtered, and their carcasses were chilled and processed to determine the effects of injecting calcium chloride (CaCl2) on beef steak palatability and quality traits. Top loin and inside round subprimals were removed from each carcass using industry fabrication procedures. No injection (control) or injection of 200 mM CaCl2 at 5% (wt/wt) was applied at 30 h postmortem to subprimals from alternating right and left sides. After vacuum storage for 7 d postmortem at 2 degrees C, 2.54-cm thick steaks were cut from each subprimal. Eighty-six percent of the control longissimus lumborum (LL) steaks and 78% of the semimembranosus (SM) control steaks had Warner-Bratzler (WBS) values > 4.5 kg, and the injection of CaCl2 reduced this percentage to 43 and 24%, respectively. The injection of CaCl2 improved (P < .05) trained sensory tenderness ratings for both LL and SM, while not affecting (P > .05) flavor intensity or causing any off-flavor problems (P > .05), compared with the controls. Lean color scores for the LL were not affected (P > .05) by the injection of CaCl2, but SM lean color was lighter red (P < .05) than controls. Therefore, a 5% (wt/wt) injection of 200 mM CaCl2 solution can be applied under commercial conditions to improve beef steak tenderness and reduce tenderness variation without detrimental effects on other palatability or quality traits.

Animals↗
PubMed1994

Temporal response of rabbits to beta-adrenergic agonist feeding: tissue weight, calpains and calpastatin activities, and nucleic acid and protein concentrations.

Forty-eight crossbred rabbits were used in three replications of a 2 x 4 factorial arrangement to investigate the short-term responses of tissue accretion, calpains and calpastatin activity, and nucleic acid and protein concentrations to beta-adrenergic agonist (BAA) feeding. Rabbits were fed a 17% CP diet with or without 7 ppm of L644,969 and slaughtered after 1, 4, 8, or 16 d of treatment. Empty body dressing percentage and biceps femoris weight (as a percentage of empty body weight [EBW]) were significantly higher in the treated rabbits than in the controls after 16 d of treatment. Heart and liver weights (as a percentage of EBW) were higher (P < .05) after 1 d and liver weight (as a percentage of EBW) was lower (P < .05) after 16 d in treated vs controls. Except for an elevation of skeletal muscle m-calpain after 16 d, BAA-supplementation did not affect the calpain-calpastatin system. Muscle RNA concentrations and RNA:DNA ratios were higher (P < .05) in treated rabbits after 1 d and remained higher thereafter. Protein:RNA ratios were lower (P < .01) in treated than in control rabbits after 4 d and remained lower throughout the trial. Muscle DNA content was lower after 4 d and higher after 16 d; RNA content was higher after 4, 8, and 16 d; and protein content was higher after 16 d in treated vs control rabbits. Liver nucleic acid and protein concentrations were not affected by BAA treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Agonists↗
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

Bovine skeletal muscle calpastatin: cloning, sequence analysis, and steady-state mRNA expression.

Calpastatin is a specific inhibitor of the calpains. Calpains play a key role in postmortem tenderization of meat and have been hypothesized to be involved in muscle protein degradation in living tissue. Isolation, cloning of complementary DNA, and nucleotide sequencing of bovine calpastatin from the longissimus muscle have been completed. Two clones were identified that encompass the entire coding sequence. Clone pCR41, derived by reverse transcription-PCR, covers domains L and 1; clone pBSA1, obtained from cDNA library screening, covers domains 2 through 4 in addition to the 3'-nontranslated region. Nucleotide sequence analysis of the cDNA for bovine calpastatin revealed an average nucleotide sequence identity of approximately 70 to 80% compared with published calpastatin nucleotide sequences of human, rabbit, and pig. Exon 3, corresponding to a highly conserved 22-amino acid region, was deleted from bovine calpastatin domain L. The calculated molecular weight of bovine skeletal muscle calpastatin of 706 amino acid residues (M(r) 75,842) corresponds to the value of purified bovine skeletal muscle calpastatin as determined by SDS-PAGE (M(r) 68,000). Northern blot analysis revealed the presence of multiple calpastatin mRNA transcripts having estimated sizes of 3.8, 3.0, and 1.5 kb in beef and 3.8, 3.0, 2.5, and 1.5 kb in sheep. Calpastatin mRNA expression was increased with beta-adrenergic agonist-induced muscle hypertrophy.

Amino Acid Sequence↗
PubMed1994

Breed effects and retained heterosis for growth, carcass, and meat traits in advanced generations of composite populations of beef cattle.

Retained heterosis for growth, carcass, and meat traits was estimated in F3 generation castrate male progeny in three composite populations finished on two levels of dietary energy density (2.82 Mcal of ME and 3.07 Mcal of ME and 11.50% CP) and serially slaughtered at four end points at intervals of 20 to 22 d. Breed effects were evaluated in nine parental breeds (Red Poll [R], Hereford [H], Angus [A], Limousin [L], Braunvieh [B], Pinzgauer [P], Gelbvieh [G], Simmental [S], and Charolais [C] that contributed to the three composite populations (MARC I = 1/4 B, 1/4 C, 1/4 L, 1/8 H, 1/8 A; MARC II = 1/4 G, 1/4 S, 1/4 H, 1/4 A; and MARC III = 1/4 R, 1/4 P, 1/4 H, and 1/4 A). Breed effects were important (P < .01) for carcass weight, dressing percentage, fat thickness, and marbling score; for retail product, fat trim and bone percentages and weights at two levels of fat trim (8 and 0 mm); and for carcass lean, fat, and bone percentages and weights. Mean slaughter weight was 54.7 kg greater for the Simmental, Gelbvieh, and Charolais breeds than for the Limousin but did not differ (P > .05) from Limousin in retail product weight or carcass lean weight because of higher dressing percentage, lower fat trim percentage, and lower bone percentage of Limousin. The effects of dietary energy density were important (P < .01) for most traits. The interaction of breed group x dietary energy density generally was not important. Retained heterosis generally was significant for each composite population for weight of retail product, fat trim, bone, and carcass lean, fat, and bone. For percentage of retail product, fat trim, carcass lean, carcass fat, and chemical fat in the 9-10-11th rib cut, generally, heterosis was significant for composites MARC II and MARC III but not for composite MARC I (i.e., composites MARC II and MARC III had a lower percentage of retail product and carcass lean and a higher percentage of fat trim, carcass fat, and chemical fat in the 9-10-11th rib cut than the mean of contributing purebreds).

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

Breed effects, retained heterosis, and estimates of genetic and phenotypic parameters for carcass and meat traits of beef cattle.

Retained heterosis for meat traits was estimated in F3 generation castrate males in three composite populations of beef cattle finished on two levels of dietary energy density (2.82 Mcal of ME and 3.07 Mcal of ME and 11.50% CP) and serially slaughtered at four end points at intervals of 20 to 22 d. Breed effects were evaluated in nine parental breeds (Red Poll [R], Hereford [H], Angus [A], Limousin [L], Braunvieh [B], Pinzgauer [P], Gelbvieh [G], Simmental [S], and Charolais [C]) that contributed to the three composite populations (MARC I = 1/4 B, 1/4 C, 1/4 L, 1/8 H, 1/8 A; MARC II = 1/4 G, 1/4 S, 1/4 H, 1/4 A; and MARC III = 1/4 R, 1/4 P, 1/4 H, and 1/4 A). Breed effects were important (P < .01) for all carcass and meat traits evaluated. Dietary energy density and slaughter group affected (P < .05) most traits evaluated. The effects of retained heterosis were not consistent among composites. For the mean of the three composites, retained heterosis was significant only for percentage of 9-10-11th rib fat and for percentage of retail product. Phenotypic correlations indicated that marbling score was a poor predictor of palatability attributes of individual carcasses. Estimates of heritability were intermediate to high for measures of fatness but were generally low for palatability attributes. The high negative genetic correlation (-.56) between percentage of retail product and marbling score and the relatively low genetic correlations between percentage of retail product and palatability attributes suggests the need for simultaneous attention to percentage of retail product and palatability attributes rather than to marbling score. Correlations among breed group means were generally high for measures of fatness with palatability attributes and were high and negative for percentage of retail product with marbling score and with other measures of fatness. Limited opportunity exists for selecting among breeds to achieve high levels of marbling in the longissimus muscle simultaneously with a high percentage of retail product. These results suggest that the most logical approach to resolution of the genetic antagonism between favorable carcass composition and less favorable palatability attributes is to form composite breeds with breed contributions organized to achieve an optimum balance between favorable carcass composition and desirable palatability attributes at optimum slaughter weights.

Analysis of Variance↗
PubMed1994

Prerigor and postrigor changes in tenderness of ovine longissimus muscle.

A novel approach was used to measure the tenderness of prerigor ovine longissimus thoracis et lumborum by avoiding the confounding effects of heat-induced shortening resulting from cooking prerigor meat. The objective was to determine the tenderness of the muscle at the time of slaughter and to monitor changes in tenderness during rigor development and postmortem aging. Nine Romanov and 12 Finnsheep rams were slaughtered at 49.3 kg live weight. Samples of longissimus thoracis et lumborum were removed at 0, 3, 6, 9, 12, 24, 72, or 336 h after exsanguination. Five of the eight sample times were represented in each carcass and all carcasses were sampled at 0, 12, and 24 h. Prerigor muscle samples (0, 3, 6, 9, and 12 h) were clamped between two metal plates before excision to prevent shortening. The samples were frozen at -30 degrees C then stored at -5 degrees C for 10 d to allow glycolysis to proceed to completion, and thus ultimate pH and complete rigor mortis were attained. The longissimus thoracis et lumborum was then cut into chops and cooked and shear force was determined. Sarcomere length decreased through 24 h postmortem, then increased slightly through 336 h postmortem. Warner-Bratzler shear force values were 5.1 kg at 0 and 3 h, increased to 8.3 kg from 3 to 9 h, and then declined to 3.1 kg from 24 to 336 h postmortem. These data imply that longissimus thoracis et lumborum at slaughter is intermediate in tenderness, rigor shortening toughens the meat, and proteolysis tenderizes the meat, resulting in more tender meat after 14 d of aging than at slaughter.

Animals↗
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↗
PubMed1994

Effects of cooking and shearing methodology on variation in Warner-Bratzler shear force values in beef.

Longissimus lumborum between the 13th rib and the 4th lumbar vertebra from 57 steers was obtained at 48 h postmortem, stored at 2 degrees C, and frozen after 7 d postmortem. Consecutive 2.54-cm-thick, paired steaks were used to make the following comparisons: Protocol A) steaks were broiled to 70 degrees C, chilled 24 h at 3 degrees C, cored parallel to fiber orientation, and sheared with a Warner-Bratzler attachment to the Instron and Protocol B) steaks were modified-oven-broiled to 65 degrees C, cooled 30 min at 23 degrees C, cored perpendicular to the steak surface, and sheared with a Warner-Bratzler shear machine. Each of the four differences in protocol was subsequently compared one at a time with paired steaks. Protocol A resulted in higher (P < .05) shear force values than Protocol B (6.29 vs 3.60 kg). Neither shearing instrument nor cooling condition contributed to the difference (P > .05) in shear values. However, parallel vs perpendicular core orientation (6.31 vs 4.51 kg, respectively) and broil to 70 degrees C vs modified-oven broil to 65 degrees C cooking method (6.37 vs 5.31 kg, respectively) increased (P < .05) shear force values. Total variance (6.2 vs 1.2 kg2) and the proportion of variance in shear value attributed among animals was greater (P < .05) for Protocol A than for Protocol B (70.0 vs 44.5%). These data indicate that Protocol A resulted in greater animal differences in shear values, and thus was more discriminating than Protocol B.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Comparison of proteolytic variables in a lean and obese strain of pig at the ages of 2.5 and 7 months.

The mode(s) of skeletal muscle protein turnover as well as muscle and animal growth may be studied by using lean and obese animals as models. The objectives of this study were to look at proteolytic variables implicated in these processes. A lean and obese strain of swine from similar genetic lineage (Duroc x Yorkshire, 50:50) have been well established and may prove ideal for this purpose. This study was done in two phases. Phase I included eight lean and eight obese pigs at 2.5 months of age, and phase II was identical, but the pigs were 7 months old. Longissimus muscle samples were processed immediately after euthanasia for activity measurements of mu-calpain, m-calpain, calpastatin, and lysosomal cathepsins B and B + L. Additional samples were taken for DNA, RNA, and total protein determinations. In phase I, total calpastatin activity, total and specific cathepsin B+L activity, and total protein/g muscle were greater in the obese pigs than in the lean pigs. In contrast, DNA and RNA/g muscle were greater in the lean pigs. No other differences were observed in phase I. In phase II, total calpastatin activity and total cathepsin B activity were greater in the obese pigs than in the lean pigs. No other differences were observed in phase II. From phase I to phase II, mu-calpain total activity increased in the lean pigs but not in the obese pigs and calpastatin activity decreased in both lean and obese pigs; however, the phase-II-obese and phase-I-lean total calpastatin concentrations were not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1993

Effects of postmortem injection time, injection level, and concentration of calcium chloride on beef quality traits.

Two experiments were conducted to determine the optimum protocol for maximizing meat quality with CaCl2 injection. Experiment 1 compared the effects of 30 min or 24 h postmortem injection of 175 mM CaCl2 or water at 10% (wt/wt) to controls on various measures of meat quality. An injection of CaCl2 reduced (P < .05) shear force values in all three beef muscles evaluated (longissimus, semimembranosus, and triceps brachii). Retail lean color was not affected (P > .05) by a CaCl2 injection at 24 h postmortem, but was slightly darker (P < .05) for an injection at 30 min postmortem. Psychrophilic and total aerobic microbial counts were higher (P < .05) in 30-min than in 24-h treatments and were higher (P < .05) in CaCl2- or water-injected semimembranosus muscle than in the control, but the treatment differences were minimal in 24-h injected meat. Experiment 2 compared the effects of 24-h postmortem injection of 200 mM or 250 mM CaCl2 at either 5 or 10% (wt/wt) to controls on meat quality traits. Both 200 and 250 mM CaCl2 reduced (P < .05) shear force values compared with the control. In addition, variation in shear force was decreased (P < .05) with CaCl2 injection. Beef flavor intensity was slightly lower (P < .05) and off-flavor ratings were slightly higher (P < .05) in CaCl2-injected meat, but the small differences were of no practical significance. Retail lean color was not affected (P > .05) by injection of the CaCl2 at 24 h. Injecting 200 mM CaCl2 at 5% (wt/wt) into 24 h postmortem meat can produce consistently tender meat without compromising other palatability or lean quality traits.

Animals↗
PubMed1993

Effect of castration on myofibrillar protein turnover, endogenous proteinase activities, and muscle growth in bovine skeletal muscle.

The effect of castration on endogenous proteinase activity and myofibrillar protein turnover was investigated in cattle. Six each of MARC III composite bulls and steers weighing approximately 210 kg were given ad libitum access to a typical growing diet. At 0, 42, 84, 126, and 168 d, two consecutive 24-h urine samples were obtained. Urine was analyzed for N tau-methylhistidine (N tau MH) and creatinine. Following slaughter after 170 d on feed, a longissimus muscle sample was removed immediately from each carcass for quantification of mu-calpain, m-calpain, calpastatin, cystatin(s), cathepsin B, and cathepsin B + L activities. Bulls were heavier (P < .05) at 126 and 168 d and more efficient (P < .05) in conversion of feed to gain at 84 and 168 d than were steers. Compared with steers, bulls excreted less (P < .05) N tau MH at 84, 126, and 168 d and displayed lower (P < .05) fractional degradation rates (FDR) at all sample times. No differences (P > .05) in calpain or cathepsin activities were observed between bulls and steers. However, muscle from bulls had greater (P < .05) activities of calpastatin and cystatin(s) than that from steers. A negative relationship existed between d-168 FDR and calpastatin (r = -.72; P < .05) and cystatin (r = -.62; P < .05) activities. These results indicate that decreased FDR of skeletal muscle from growing bulls contributes to their greater efficiency of growth and could be related partially to cystatin-mediated cathepsin activity and(or) calpastatin-mediated calpain activity.

Animals↗
PubMed1993

Effects over time of feeding a beta-adrenergic agonist to wether lambs on animal performance, muscle growth, endogenous muscle proteinase activities, and meat tenderness.

Forty wether lambs were used in a 2 x 4 factorial arrangement to determine the response of animal performance, muscle growth, proteinase activity, and meat tenderness to beta-adrenergic agonist (BAA) supplementation. Lambs were fed a finishing diet with or without 4 ppm of L644,969 and slaughtered after 0, 2, 4, and 6 wk of treatment. The ADG was higher (P < .05) in the treated than in the control lambs after 2 wk and returned to control levels thereafter. Semitendinosus weight and calpastatin activity were higher and mu-calpain activity was lower in the treated than in the control lambs after 2, 4, and 6 wk. Cathepsin B activity was higher (P < .01) and cystatin-like activity was lower (P < .05) after 2 wk in treated than in control lambs but returned to control levels thereafter. Longissimus protein:DNA was higher after 4 (P < .05) and 6 (P < .01) wk in the treated lambs than in the controls. The concentration of RNA and RNA:DNA ratio were higher (P < .01) in the longissimus and semitendinosus muscles in the treated lambs after 2 wk and remained higher throughout the study. Semitendinosus protein and RNA content were higher after 2, 4, and 6 wk and DNA content was higher after 2 and 6 wk in the treated than in the control lambs. Longissimus shear-force values were higher (P < .001) in the treated than in the control lambs at all slaughter end points. These data indicate a rapid alteration of muscle growth, activity of the calpain-calpastatin system, and meat tenderness during BAA treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Agonists↗
PubMed1992

The role of Ca(2+)-dependent proteases (calpains) in post mortem proteolysis and meat tenderness.

This manuscript summarizes research results from our laboratory regarding the role of endogenous proteases in post mortem proteolysis resulting in meat tenderization. Proteolysis of key myofibrillar proteins is the principal reason for ultrastructural changes in skeletal muscle associated with meat tenderization. Proteases should have the following characteristics to be considered as possible candidates for bringing about post mortem changes: i) to be located within skeletal muscle cells; ii) to have access to the substrate ie, myofibrils); and iii) to be able to hydrolyze the same proteins that are degraded during post mortem storage. Of the proteases located within skeletal muscle cells and thus far characterized, only calpains have all of the above characteristics. Numerous experiments conducted in our laboratory have indicated that the calcium-dependent proteolytic system (calpains) is responsible for post mortem proteolysis. Some of this evidence includes: 1) incubation of muscle slices with buffer containing Ca2+ accelerates post mortem proteolysis; 2) incubation of muscle slices with Ca2+ chelators inhibits post mortem proteolysis; 3) infusion or injection of carcasses with a solution of calcium chloride accelerates post mortem proteolysis and the tenderization process such that post mortem storage beyond 24 h to ensure meat tenderness is no longer necessary; 4) infusion of carcasses with zinc chloride, a potent inhibitor of calpains, blocks post mortem proteolysis and the tenderization process; and 5) feeding a beta-adrenergic agonist to lambs results in a reduction of the proteolytic capacity of the calpain system, which leads to a decreased rate of post mortem proteolysis and produces tough meat.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗