Detection of quantitative trait loci for growth and carcass composition in cattle

The objective of the present study was to detect quantitative trait loci for economically important traits in a family from a Bos indicus x Bos taurus sire. A Brahman x Hereford sire was used to develop a half-sib family (n = 547). The sire was mated to Bos taurus cows. Traits analyzed were birth (kg) and weaning weights (kg); hot carcass weight (kg); marbling score; longissimus area (cm2); USDA yield grade; estimated kidney, pelvic, and heart fat (%); fat thickness (cm); fat yield (%); and retail product yield (%). Meat tenderness was measured as Warner-Bratzler shear force (kg) at 3 and 14 d postmortem. Two hundred and thirty-eight markers were genotyped in 185 offspring. One hundred and thirty markers were used to genotype the remaining 362 offspring. A total of 312 markers were used in the final analysis. Seventy-four markers were common to both groups. Significant QTL (expected number of false-positives < 0.05) were observed for birth weight and longissimus area on chromosome 5, for longissimus area on chromosome 6, for retail product yield on chromosome 9, for birth weight on chromosome 21, and for marbling score on chromosome 23. Evidence suggesting (expected number of false-positives < 1) the presence of QTL was detected for several traits. Putative QTL for birth weight were detected on chromosomes 1, 2, and 3, and for weaning weight on chromosome 29. For hot carcass weight, QTL were detected on chromosomes 10, 18, and 29. Four QTL for yield grade were identified on chromosomes 2, 11, 14, and 19. Three QTL for fat thickness were detected on chromosomes 2, 3, 7, and 14. For marbling score, QTL were identified on chromosomes 3, 10, 14, and 27. Four QTL were identified for retail product yield on chromosomes 12, 18, 19, and 29. A QTL for estimated kidney, pelvic, and heart fat was detected on chromosome 15, and a QTL for meat tenderness measured as Warner-Bratzler shear force at 3 d postmortem was identified on chromosome 20. Two QTL were detected for meat tenderness measured as Warner-Bratzler shear force at 14 d postmortem on chromosomes 20 and 29. These results present a complete scan in all available progeny in this family. Regions underlying QTL need to be assessed in other populations.     

Phenotypic ranges and relationships among carcass and meat palatability traits for fourteen cattle breeds, and heritabilities and expected progeny differences for Warner-Bratzler shear force in three beef cattle breeds

Carcass and Warner-Bratzler shear force (WBSF) data from strip loin steaks were obtained from 7,179 progeny of Angus, Brahman, Brangus, Charolais, Gelbvieh, Hereford, Limousin, Maine-Anjou, Red Angus, Salers, Shorthorn, Simbrah, Simmental, and South Devon sires. Trained sensory panel (TSP) evaluations were obtained on 2,320 steaks sampled from contemporary groups of progeny from one to five sires of each breed. Expected progeny differences for marbling and WBSF were developed for 103 Simmental sires from 1,295 progeny, 23 Shorthorn sires from 310 progeny, and 69 Hereford sires from 1,457 progeny. Pooled phenotypic residual correlations, including all progeny, showed that marbling was lowly correlated with WBSF (-0.21) and with TSP overall tenderness (0.18). The residual correlation between WBSF and TSP tenderness was -0.68, whereas residual correlations for progeny sired by the three Bos indicus breeds were only slightly different than for progeny sired by Bos taurus breeds. The phenotypic range of mean WBSF among sires across breeds was 6.27 kg, and the phenotypic range among breed means was 3.93 kg. Heritability estimates for fat thickness, marbling score, WBSF, and TSP tenderness, juiciness, and flavor were 0.19, 0.68, 0.40, 0.37, 0.46, and 0.07, respectively. Ranges in EPD for WBSF and marbling were -0.41 to +0.26 kg and +0.48 to -0.22, respectively, for Simmentals; -0.41 to +0.36 kg and 0.00 to -0.32, respectively, for Shorthorns; and -0.48 to +0.22 kg and +0.40 to -0.24, respectively, for Herefords. More than 20% of steaks were unacceptable in tenderness. Results of this study demonstrated that 1) selection for marbling would result in little improvement in meat tenderness; 2) heritability of marbling, tenderness, and juiciness are high; and 3) sufficient variation exists in WBSF EPD among widely used Simmental, Shorthorn, and Hereford sires to allow for genetic improvement in LM tenderness.     

Effect of postmortem treatments on the tenderness of meat from Hereford, Brahman and Brahman-cross beef cattle

The effect of postmortem aging (7, 14, 21 or 28 d), high-voltage electrical stimulation (stimulated or not stimulated) and blade tenderization (none or once; crossbreds only) on the sensory and cooking properties of meat from four beef breeds or breed-types (purebred Hereford, purebred Brahman, Hereford x Brahman and Brahman x Hereford) was determined. The meat from purebred Brahman cattle that was not electrically stimulated was less tender and more variable in tenderness than that from other breed-types but electrical stimulation reduced these differences in tenderness. The Brahman crossbred steers produced meat that was not different in tenderness or variability in tenderness from that of purebred Hereford steers, although all were only judged "slightly tender." Electrical stimulation reduced the length of postmortem aging needed to reach a given level of tenderness regardless of breed or breed-type. Meat from crossbred animals that was blade-tendernized was not different in tenderness from meat that was electrically stimulated. The results of this investigation indicate that purebred Brahman muscle was inherently less tender, but postmortem tenderization procedures produced meat that was similar tenderness to that of the other breed-types used in this study.     

The use of vitamin D3 to improve beef tenderness

An experiment was designed to test the hypothesis that short-term oral administration of dietary vitamin D3 to beef cattle before slaughter would increase beef tenderness through greater calcium-activated calpain activity in postmortem aged skeletal muscle. Thirty continental crossbred steers were allotted randomly to three treatment groups housed in one pen. One group served as a control; two other groups were administered boluses with either 5 x 10(6) or 7.5 x 10(6) IU of vitamin D3 daily for 9 d. Cattle were slaughtered 1 d later. The longissimus lumborum was excised from each carcass 72 h postmortem and steaks removed at 3, 7, 14, and 21 d postmortem. The semimembranosus muscle (top round) was excised from each carcass 72 h postmortem and steaks removed at 7, 14, and 21 d postmortem. Blood plasma calcium concentration of cattle treated with 5 or 7.5 x 10(6) IU of vitamin D3 was higher (P < .05) than that of controls. Strip loin and top loin steaks from cattle fed supplemental doses of vitamin D3 had lower (P < .05) Warner-Bratzler (W-B) shear values at 14 d postmortem but were not significantly different from controls at 3, 7, or 21 d (strip loins) or 7 or 21 d (top rounds). No significant difference in strip loin steak tenderness was observed by sensory panel at 14 d postmortem (P < .17) between steaks from control and vitamin D3-treated steers. At 14 d postmortem, strip loin and top round steaks from cattle fed 5 x 10(6) IU of vitamin D3, but not from those given 7.5 x 10(6) IU, showed more proteolysis (P < .05) than did steaks from control cattle, based on Western blotting analysis. Therefore, the use of supplemental dietary vitamin D3 given daily for 9 d before slaughter did improve tenderness (lower W-B shear values) of 14-d postmortem aged beef. Increased proteolysis seems to be the mechanism of tenderization.     

Supranutritional oral supplementation with vitamin D3 and calcium and the effects on beef tenderness

Ultimate meat tenderness can be influenced by numerous preslaughter and postmortem management techniques. Increased levels of intracellular Ca2+, through postmortem injection, infusion, or marination, have been shown to improve the tenderness of cooked meat products. Oral supplementation with vitamin D3 effectively increases serum Ca2+ and has been hypothesized to increase muscle Ca2+ content, the activity of muscle proteases, and thus the tenderness of cooked beef. Individual Charolais x Hereford heifers (n = 191) were assigned to an unsupplemented control group or groups that were supplemented via oral bolus (for dose regulation purposes) with one of seven levels of vitamin D3 (1, 2, 3, 4, or 5 x 10(6) IU D3/d, 2 x 10(6) IU DS/d plus 75 g CaCO3 or 4 x 106 IU D3/d plus 75 g CaCO3) for 2, 4, 6, or 8 d antemortem. Individual feedlot performance, serum Ca2+ levels, and carcass data were collected, and eight longissimus steaks/carcass were used to obtain Warner-Bratzler shear force values measured at 2, 7, 14, and 21 d postmortem for longissimus steaks cooked to 70 degrees or 85 degrees C. Cattle supplemented with 4 x 10(6) IU D3/d plus 75 g of CaCO3 had lower daily feed intake (as-fed) and reduced (P < 0.05) average daily gains compared with controls during the 8-d supplementation period. Additionally, supplemented cattle had numerically higher dressing percentages, possibly due to less fill at the time of slaughter, because carcass weights and USDA yield grades did not differ (P > 0.05) across treatment groups. Supplementation with 1, 2, 3, 4, or 5 x 10(6) IU D3/d, for 2 or more days, increased (P < 0.05) serum Ca2+ concentrations compared with controls. Whereas cattle that received additional dietary Ca2+ in the form of CaCO3 had the lowest blood serum Ca2+ concentration. Although blood serum Ca2+ was increased, supplementation with any level of vitamin D3 for any length of time up to 8 d did not improve (P > 0.05) Warner-Bratzler shear force at 2, 7, 14, or 21 d of postmortem aging compared with controls when steaks were cooked to final internal temperatures of either 70 (control means 6.27, 4.91, 4.64, and 3.80 kg, respectively) or 85 degrees C (control means 7.31, 5.32, 4.69, and 4.46 kg, respectively). Results indicated that oral supplementation with vitamin D3 (at high or low doses) for 2 to 8 d before slaughter increased serum Ca2+ concentration but does not improve cooked longissimus tenderness.     

Effects of ractopamine supplementation and postmortem aging on longissimus muscle palatability of beef steers differing in biological type

Effects of ractopamine hydrochloride (RAC) supplementation and postmortem aging on palatability of beef from steers differing in biological type were evaluated using LM samples from British, Continental crossbred, and Brahman crossbred calf-fed steers (n = 98/type). Equal numbers of steers within each type were assigned to treatments of 0 or 200 mg.steer(-1).d(-1) of RAC fed during the final 28 d of the finishing period. Warner-Bratzler shear force (WBSF) was measured at 3, 7, 14, and 21 d postmortem, and trained sensory panel (TP) evaluation was conducted using LM samples aged for 14 d postmortem. A RAC x type interaction (P = 0.006) was detected for WBSF. Within each type, steers fed RAC produced steaks with greater (P < 0.05) WBSF values than steaks from control steers; however, the magnitude of the effect of RAC on WBSF was more pronounced among Brahman cross-breds (5.53 vs. 4.96 +/- 0.10 kg) than among Continental crossbred (4.16 vs. 3.96 +/- 0.10 kg) and British steers (4.10 vs. 3.75 +/- 0.10 kg). The effect of RAC on WBSF, though diminished slightly by aging (mean WBSF difference: 3 d = 0.49 kg; 21 d = 0.24 kg), was not completely mitigated by 21 d of postmortem storage (P(RAC x AGE) = 0.16). Steers fed RAC produced steaks that received lower (P < 0.05) TP ratings for tenderness (8.09 vs. 8.95 +/- 0.18) and juiciness (7.41 vs. 8.07 +/- 0.16 kg), along with slightly lower (P = 0.06) ratings for beef flavor (6.67 vs. 6.93 +/- 0.10 kg), compared with steaks from unsupplemented steers, regardless of biological type. Among the 3 biological types, Brahman crossbred cattle produced steaks with the greatest (P < 0.05) WBSF values at each aging period; WBSF values for steaks from British and Continental type steers did not differ (P > 0.05) at any aging time. Sensory panel ratings of tenderness, juiciness, and beef flavor were greatest (P < 0.05) for steaks from British steers, and least (P < 0.05) for steaks produced by Brahman-type steers. Results from this study suggest that RAC supplementation slightly decreases LM tenderness (WBSF and TP) of British, Continental crossbred, and Brahman cross-bred steers, and that the effect of RAC on WBSF may be more pronounced in steaks from Brahman crossbred cattle than among stenks from Continental type or British steers.     

Characterization of estrogen-trenbolone acetate implants on tenderness and consumer acceptability of beef under the effect of 2 aging times

Anabolic steroid implants are commonly used to increase growth performance and carcass leanness. The objective of this study was to determine the effects of various trenbolone acetate implants on Warner-Bratzler shear force (WBSF), slice shear force, and consumer palatability ratings for USDA Choice and Select beef strip steaks aged for 14 and 21 d from cattle implanted before slaughter. Beef steers (n = 1,740) were subjected to the following treatments: 1) nonimplanted control (CON); 2) Revalor-IS on d 0 and Revalor-S on d 70 (IS/S); or 3) Revalor-XS (RXS) on d 0, and were randomly assigned to pens within blocks. A subsample of USDA Choice (n = 82) and USDA Select (n = 81) carcasses was selected. Strip loins from these carcasses were collected, and steaks measuring 2.54 cm were fabricated and aged for 14 or 21 d postmortem. Select steaks aged 14 d from RXS cattle had decreased (P < 0.05) WBSF values compared with IS/S steaks, but CON steaks did not differ from either implant treatment. Warner-Bratzler shear force did not differ among treatments (P > 0.05) from USDA Choice steaks aged 14 and 21 d or from Select steaks aged 21 d. Consumer scores for flavor and overall liking for USDA Choice 14-d aged RXS steaks were less (P < 0.05) than CON steaks; however, there were no differences between RXS, IS/S, and CON for tenderness or juiciness, or for tenderness and overall acceptability. Select steaks aged 14 d from IS/S cattle had less (P < 0.05) tenderness, tenderness acceptability, overall acceptability, overall liking, juiciness, and flavor scores than RXS and CON steaks; however, consumers also rated RXS steaks less for tenderness, juiciness, and tenderness acceptability when compared with CON steaks. Consumer scores for overall liking, flavor, and tenderness for USDA Choice steaks aged 21 d from RXS, IS/S, and CON did not differ. However, implant affected (P < 0.05) overall liking, flavor, juiciness, and tenderness for USDA Select steaks aged 21 d. Even so, there were no differences between RXS, IS/S, and CON steaks for tenderness or overall acceptability for steaks aged 21 d, regardless of quality grade. Results indicated that tenderness differences exist among implant strategies when strip steaks were aged 14 d; however, tenderness and overall consumer acceptability were only influenced by implant in Select steaks aged 14 d. Furthermore, aging for 21 d can minimize and even eliminate implant differences in WBSF and slice shear force, as well as tenderness and overall consumer acceptability.     

Effect of two dietary concentrate levels on tenderness, calpain and calpastatin activities, and carcass merit in Waguli and Brahman steers

The objective of this study was to compare carcass characteristics of a newly introduced breed, the Waguli (Wagyu x Tuli), with the carcass characteristics of the Brahman breed. Brahman cattle are used extensively in the Southwest of the United States because of their tolerance to adverse environmental conditions. However, Brahman carcasses are discounted according to the height of their humps because of meat tenderness issues. The Waguli was developed in an attempt to obtain a breed that retained the heat tolerance of the Brahman but had meat quality attributes similar to the Wagyu. Twenty-four animals were used. Six steers from each breed were fed a 94% concentrate diet and 6 steers from each breed were fed an 86% concentrate diet. Eight steers, 2 from each group, were harvested after 128 d, after 142 d, and after 156 d on feed. Waguli steers had larger LM, greater backfat thickness, greater marbling scores, and greater quality grades than the Brahman steers (P < 0.05). The Japanese Wagyu breed is well known for its highly marbled and tender meat, and these traits are also present in the Waguli. The Waguli had significantly lower Warner-Bratzler shear force values than the Brahman steers after 7 and 10 d of postmortem aging (P < 0.05); this difference decreased after 14 d postmortem (P = 0.2), when tenderness of the slower aging Brahman had increased to acceptable levels. Toughness of the Brahman has been associated with high levels of calpastatin in Brahman muscle, and the Waguli LM had significantly less calpastatin activity (P = 0.02) at 0 h postmortem than the Brahman LM. At 0-h postmortem, the total LM calpain activity did not differ between the Brahman and Waguli (P = 0.57). Neither diet nor days on feed had any significant effect on the 0-h postmortem calpain or at 0-h postmortem calpastatin activity, nor an effect on Warner-Bratzler shear-force values. In conclusion, LM muscle from the Waguli steers had a high degree of marbling, lower shear force values, and low calpastatin activity, all of which are related to more tender meat.     

A putative quantitative trait locus on chromosome 20 associated with bovine pathogenic disease incidence

The objective of this study was to detect QTL associated with the incidence of multiple pathogenic diseases in offspring from half-sib bovine families. Four F(1) sires were used to produce offspring: Brahman x Hereford (BH; n = 547), Piedmontese x Angus (PA; n = 209), Brahman x Angus (n = 176), and Belgian Blue x MARC III (n = 246). Treatment records for bovine respiratory disease, infectious keratoconjunctivitis (pinkeye), and infectious pododermatitis (footrot) were available for all of the offspring from birth to slaughter. The incidences of these 3 microbial pathogenic diseases were combined into a single binary trait to represent an overall pathogenic disease incidence. Offspring diagnosed and treated for 1 or more of the previously mentioned pathogenic diseases were coded as a 1 for affected. Cattle with no treatment record were coded as 0 for healthy. A putative QTL for pathogenic disease incidence was detected in the family derived from the BH sire at the genome-wise suggestive level. This was supported by evidence, in the same chromosomal region, of a similar QTL in the family derived from the PA sire. The maximum F-statistic (F = 13.52; P = 0.0003) was located at cM 18. The support interval of the QTL spanned from cM 9 to 28. Further studies should explore this QTL by using other bovine populations to further confirm the QTL and refine the QTL support interval. Offspring inheriting the Hereford allele, in the family from the BH sire, and the Angus allele, in the family from the PA sire, were less susceptible to incidence of pathogenic diseases, when compared with those inheriting the Brahman allele and Piedmontese allele, from the BH and PA sires, respectively.     

Effects of slaughter weight and carcass electrical stimulation on the quality and palatability of beef from young purebred bulls

Seventy-eight purebred Angus and Brahman bulls (10 to 18 mo at slaughter) were used to determine the effects of slaughter weight (60, 80, 90 or 100% of the average mature-cow weight for the respective breed) and carcass electrical stimulation (500 V, 20 2-s impulses on the right side) on carcass and meat characteristics. Angus bulls grazed summer forage (millet) after weaning, while Brahman bulls were fed to stimulate gains achieved on forage by Angus bulls. Bulls were then placed in the feedlot for finishing to their designated slaughter weight (293, 381, 412 and 463 kg for Angus and 316, 420, 463 and 516 kg for Brahman). Coarse dark band formation and lean color problems normally associated with bullock carcasses were either eliminated or reduced by stimulation. Increasing slaughter weight from 60 to 90% was associated with an increase in panel tenderness scores for loin steaks. However, increasing slaughter weight from 90 to 100% little change was detected. On the other hand, shear values for loin steaks decreased with increasing slaughter weight. Stimulation increased the tenderness of loin steaks as determined by both panel scores and shear values, and of bottom round steaks (shear-force values). The data from this study suggest that meat from the bulls slaughtered at lighter weights was generally tough, but was improved when bulls were fed to heavier, yet acceptable weights. This research encourages implementation of electrical stimulation on carcasses from young bulls to improve quality-indicating factors.     

Influence of early postmortem protein oxidation on beef quality

The objective of this study was to examine the effect of early postmortem protein oxidation on the color and tenderness of beef steaks. To obtain a range of oxidation levels, the longissimus lumborum muscles (LM) from both strip loins of 20 steers fed either a finishing diet with vitamin E (1,000 IU per steer daily, minimum of 126 d [VITE]; n = 10 steers) or fed the same finishing diet without vitamin E (CON; n = 10 steers) were used. Within 24 h after slaughter, the LM muscle from each carcass was cut into 2.54-cm-thick steaks and individually vacuum packaged. Steaks from each steer were assigned to a nonirradiated group or an irradiated group. Steaks were irradiated within 26 h postmortem, and were aged at 4 degrees C for 0, 1, 3, 7, and 14 d after irradiation. Steaks from each diet/irradiation/aging time treatment were used to determine color, shear force, and degree of protein oxidation (carbonyl content). Steaks from steers fed the VITE diet had higher (P < 0.01) alpha-tocopherol contents than steaks from steers fed the CON diet. Immediately following irradiation, steaks that had been irradiated had lower (P < 0.05) L* values regardless of diet. Irradiated steaks, regardless of diet, had lower a* (P < 0.05) and b* (P < 0.01) values than nonirradiated steaks at all aging times. Carbonyl concentration was higher (P < 0.05) in proteins from irradiated steaks compared to nonirradiated steaks at 0, 1, 3, and 7 d postirradiation. Immunoblot analysis showed that vitamin E supplementation decreased the number and extent of oxidized sarcoplasmic proteins. Protein carbonyl content was positively correlated with Warner-Bratzler shear force values. These results indicate that increased oxidation of muscle proteins early postmortem could have negative effects on fresh meat color and tenderness.     

Supplemental vitamin D3 concentration and biological type of steers. II. Tenderness, quality, and residues of beef

Vitamin D3 was orally supplemented to determine the supplemental dose that improved beef tenderness in different cattle breed types. Feedlot steers (n = 142) were arranged in a 4 x 3 factorial arrangement consisting of four levels of supplemental vitamin D3 (0, 0.5, 1, and 5 million IU/steer daily) administered for eight consecutive days antemortem using three biological types (Bos indicus, Bos Taurus-Continental, and Bos Taurus-English). Warner-Bratzler shear force (WBSF) was measured at 3, 7, 10, 14, and 21 d postmortem, and trained sensory analysis was conducted at 7 d postmortem on LM, semimembranosus, gluteus medius, and supraspinatus steaks. Concentrations of vitamin D3 and the metabolites 25-hydroxyvitamin D3, and 1,25-dihydroxyvitamin D3 were determined in the LM, liver, kidney, and plasma. Biological type of cattle did not interact (P > 0.10) with vitamin D3 supplementation for sensory or tenderness traits, suggesting that feeding vitamin D3 for 8 d before slaughter affected the different biological types of cattle similarly. Supplementing steers with 0.5, 1, or 5 million IU/(steer(d) decreased (P < 0.05) LM WBSF at 7, 10, 14, and 21 d postmortem compared with controls, and vitamin D3 treatments of 0.5, 1, and 5 million IU decreased (P < 0.05) semimembranosus WBSF at 3, 7, and 14 d postmortem. In general, vitamin D3-induced improvements in WBSF were most consistent and intense in LM steaks. Sensory panel tenderness was improved (P < 0.05) by all vitamin D3 treatments in LM steaks. Sensory traits ofjuiciness, flavor, connective tissue, and off-flavor were not (P > 0.05) affected by vitamin D3 treatments. All vitamin D3 treatments decreased micro-calpain activity and increased muscle Ca concentrations (P < 0.05). Vitamin D3 concentrations were increased (P < 0.05) by supplementation in all tissues tested (liver, kidney, LM, and plasma); however, cooking steaks to 71 degrees C decreased (P < 0.05) treatment residue effects. The vitamin D metabolite 1,25-dihydroxyvitamin D3 was increased (P < 0.05) only in plasma samples as a result of the vitamin D3 treatments. These results indicate that supplementation with vitamin D3 at 0.5 million IU/steer daily for eight consecutive days before slaughter improved tenderness in steaks from different subprimal cuts by affecting muscle Ca concentrations, micro-calpain activities, and muscle proteolysis, with only a small effect on tissue residues of vitamin D3.     

Association of a single nucleotide polymorphism in the calpastatin gene with carcass and meat quality traits of beef cattle

Calpastatin (CAST) is a naturally occurring protein that inhibits the normal tenderization of meat as it ages postmortem. A SNP was identified in the CAST gene (a G to C substitution) and genotyped on crossbred commercially fed heifers (n = 163), steers (n = 226), and bulls (n = 61) from beef feedlots, and steers (n = 178) from a University of Guelph feeding trial. The association of the CAST SNP with carcass and meat quality traits was studied. Carcass traits included fat, lean, and bone yield; grade fat; LM area; and HCW. Meat quality traits included marbling grade; i.m. fat content of LM; tenderness evaluation of LM (Warner-Bratzler shear force) at 2, 7, 14, and 21 d of postmortem aging; and tenderness evaluation of semitendinosus muscle at 7 d of postmortem aging. The mixed model used in the analyses included fixed effects of CAST genotype, sex, slaughter group, and breed composition (linear covariate); sire was a random effect. For the analysis of shear force, i.m. fat content of LM was also included in the model as a linear covariate. Shear force measures were analyzed within days of postmortem aging and by repeated measures analysis. The CAST SNP allele C was more frequent (63%) in the crossbred population than allele G. The CAST SNP was associated with shear force across days of postmortem aging (P = 0.005); genotype CC yielded beef that was more tender than GG (-0.32 kg +/- 0.13), and CG had intermediate tenderness. The corresponding average allele substitution effect (G to C substitution) was also highly significant (-0.15 +/- 0.05 kg, P = 0.002). A lower percentage of unacceptably tough steaks (shear force > 5.7 kg) at 2 and 7 d postmortem was associated with an increasing number of C alleles (P < or = 0.05). At 7 d postmortem, the percentage of unacceptably tough steaks decreased by 24 and 35%, respectively, for animals carrying 1 and 2 copies of the C allele relative to animals with no C alleles. However, genotype CC had a greater fat yield (+1.44 +/- 0.56%; P = 0.037) than genotype GG, with a corresponding allele substitution effect of 0.67 +/- 0.27% (P = 0.015). Therefore, the CAST SNP allele C was associated with increased LM tenderness across days of postmortem aging and, importantly for the beef industry, had a significant reduction in the percentage of steaks rated unacceptably tough by consumers based on an assumed threshold level.     

Effect of days fed, carcass grade traits, and subcutaneous fat removal on postmortem muscle characteristics and beef palatability.

Angus x Hereford steers (n = 48) similar in frame size and in muscle thickness were allotted to eight groups (n = 6) of similar mean live weight for serial slaughter at 28-d intervals (0 to 196 d). Except for d-0 steers, which served as grass-fed controls, all steers were fed a high-concentrate diet during the finishing period. Upon slaughter, one side of each carcass was trimmed of subcutaneous fat in the wholesale rib region. Postmortem longissimus muscle (LM) temperature was monitored for each side during the 24-h chilling period. After quality and yield grade data were collected, rib steaks were removed and aged (7 d) and sensory traits of the steaks were evaluated. Most carcass grade traits increased linearly (P less than .01) with days on feed, whereas most sensory panel variables and marbling increased curvilinearly (P less than .05). Generally, after 56 d on feed, carcasses chilled at slower rates (P less than .05) with increased days fed. Taste panel tenderness, amount of perceived connective tissue, and shear force values peaked at 112 d and were slightly less desirable for cattle fed longer than 112 d (quadratic term, P less than .01). Postmortem muscle temperature at 2.5 h was the chilling time most highly correlated with tenderness values among untrimmed sides. Correlations for shear force with 2.5-h LM temperature, marbling score, days fed, fat thickness, and carcass weight were -.63, -.61, -.56, -.55, and -.53, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Quantitative trait loci affecting growth and carcass composition of cattle segregating alternate forms of myostatin

The effects of the bovine myostatin gene on chromosome 2 on birth and carcass traits have been previously assessed. The objective of this study was to identify additional quantitative trait loci (QTL) for economically important traits in two families segregating an inactive copy of myostatin. Two half-sib families were developed from Belgian Blue x MARC III (n = 246) and Piedmontese x Angus (n = 209) sires. Traits analyzed were birth (kg) and yearling weight (kg); hot carcass weight (kg); fat depth (cm); marbling score; longissimus muscle area (cm2); estimated kidney, pelvic, and heart fat (%); USDA yield grade; retail product yield (%); fat yield (%); and wholesale rib-fat yield (%). Meat tenderness was measured as Warner-Bratzler shear force at 3 and 14 d postmortem. The effect of myostatin on these traits was removed by using phase information obtained from the previous study with six microsatellite markers flanking the locus. Selective genotyping was done on 92 animals from both families to identify genomic regions potentially associated with retail product yield and fat depth, using a total of 150 informative markers in each family. Regions in which selective genotyping indicated the presence of QTL were evaluated further by genotyping the entire population and additional markers. For the family with Belgian Blue inheritance (n = 246), a significant QTL for birth and yearling weight was identified on chromosome 6. Suggestive QTL were identified for longissimus muscle area and hot carcass weight on chromosome 6 and for marbling on chromosomes 17 and 27. For the family with Piedmontese inheritance (n = 209), suggestive QTL on chromosome 5 were identified for fat depth, retail product yield, and USDA yield grade and on chromosome 29 for Warner-Bratzler shear force at 3 and 14 d postmortem. Interactions suggesting the presence of QTL were observed between myostatin and chromosome 5 for Warner-Bratzler shear force at 14 d postmortem and between myostatin and chromosome 14 for fat depth. Thus, in families segregating an inactive copy of myostatin in cattle, other loci influencing quantitative traits can be detected. These results are the initial effort to identify and characterize QTL affecting carcass and growth traits in families segregating myostatin.     

A new single nucleotide polymorphism in CAPN1 extends the current tenderness marker test to include cattle of Bos indicus, Bos taurus, and crossbred descent

The three objectives of this study were to 1) test for the existence of beef tenderness markers in the CAPN1 gene segregating in Brahman cattle; 2) test existing CAPN1 tenderness markers in indicus-influenced crossbred cattle; and 3) produce a revised marker system for use in cattle of all subspecies backgrounds. Previously, two SNP in the CAPN1 gene have been described that could be used to guide selection in Bos taurus cattle (designated Markers 316 and 530), but neither marker segregates at high frequency in Brahman cattle. In this study, we examined three additional SNP in CAPN1 to determine whether variation in this gene could be associated with tenderness in a large, multisire American Brahman population. One marker (termed 4751) was associated with shear force on postmortem d 7 (P < 0.01), 14 (P = 0.015), and 21 (P < 0.001) in this population, demonstrating that genetic variation important for tenderness segregates in Bos indicus cattle at or near CAPN1. Marker 4751 also was associated with shear force (P < 0.01) in the same large, multisire population of cattle of strictly Bos taurus descent that was used to develop the previously reported SNP (referred to as the Germplasm Evaluation [GPE] Cycle 7 population), indicating the possibility that one marker could have wide applicability in cattle of all subspecies backgrounds. To test this hypothesis, Marker 4751 was tested in a third large, multisire cattle population of crossbred subspecies descent (including sire breeds of Brangus, Beefmaster, Bonsmara, Romosinuano, Hereford, and Angus referred to as the GPE Cycle 8 population). The highly significant association of Marker 4751 with shear force in this population (P < 0.001) confirms the usefulness of Marker 4751 in cattle of all subspecies backgrounds, including Bos taurus, Bos indicus, and crossbred descent. This wide applicability adds substantial value over previously released Markers 316 and 530. However, Marker 316, which had previously been shown to be associated with tenderness in the GPE Cycle 7 population, also was highly associated with shear force in the GPE Cycle 8 animals (P < 0.001). Thus, Marker 316 may continue to be useful in a variety of populations with a high percentage of Bos taurus backgrounds. An optimal marker strategy for CAPN1 in many cases will be to use both Markers 316 and 4751.     

Assessment of single nucleotide polymorphisms in genes residing on chromosomes 14 and 29 for association with carcass composition traits in Bos indicus cattle

Objective of this study was to assess the association of SNP in the diacylglycerol O-acyltransferase 1 (DGAT1), thyroglobulin (TG), and micromolar calcium-activated neutral protease (CAPN1) genes with carcass composition and meat quality traits in Bos indicus cattle. A population of Brahman calves (n = 479) was developed in central Florida from 1996 to 2000. Traits analyzed were ADG, hip height, slaughter weight, fat thickness, HCW, marbling score, LM area, estimated KPH fat, yield grade, retail yield, sensory panel tenderness score, carcass hump height, and cooked meat tenderness measured as Warner-Bratzler shear force at 7, 14, and 21 d postmortem. Single nucleotide polymorphisms previously reported in the TG and DGAT1 genes were used as markers on chromosome 14. Two previously reported and two new SNP in the CAPN1 gene were used as markers on chromosome 29. One SNP in CAPN1 was uninformative, and another one was associated with tenderness score (P < 0.05), suggesting the presence of variation affecting meat tenderness. All three informative SNP at the CAPN1 gene were associated with hump height (P < 0.02). The TG marker was associated with fat thickness and LMA (P < 0.05), but not with marbling score. No significant associations of the SNP in the DGAT1 gene were observed for any trait. Allele frequencies of the SNP in TG and CAPN1 were different in this Brahman population than in reported allele frequencies in Bos taurus populations. The results suggest that the use of molecular marker information developed in Bos taurus populations to Bos indicus populations may require development of appropriate additional markers.     

Feeding 25-hydroxyvitamin D3 to improve beef tenderness

The objective of this trial was to determine if a single oral bolus of 25-hydroxyvitamin D3 (25-OH D3) given at various times before slaughter would enhance the tenderness of beef loin steaks. One hundred eight crossbred steers were allotted to 18 pens so that the mean weight of the cattle in each pen was similar. Treatments (25-OH D3 dose [62.5 or 125 mg]) and time of administration of the single oral bolus (4, 7, 21, or 35 d before slaughter) were assigned randomly to each pen of steers. Serial plasma samples were collected at each bolus administration time for control animals. For steers assigned to a treatment group, a baseline blood sample was collected before bolus administration and at each subsequent administration when other treatment groups received their bolus. Plasma samples were assayed for 25-OH D3 and calcium concentrations. Troponin-T degradation and Warner-Bratzler shear force were measured as indicators of tenderness for loin steaks collected at slaughter and aged for 6 or 14 d postmortem. Muscle samples, collected concurrently, were assayed for 25-OH D3 and calcium concentrations. A single oral bolus of 25-OH D3 was sufficient to increase plasma 25-OH D3 concentrations (P < 0.001) through slaughter, regardless of dose or time of bolus administration. The single oral bolus of 25-OH D3, however, did not increase plasma calcium concentrations (P > 0.05). As a result, neither troponin-T degradation nor Warner-Bratzler shear force was improved (P > 0.05) by treatment. Muscle 25-OH D3 concentrations were increased (P > 0.001) by treatment with 25-OH D3. Although sustained plasma 25-OH D3 concentrations did not increase plasma or muscle calcium at slaughter nor influence tenderness, the use of 25-OH D3 as a nutritional means of improving beef tenderness is in its infancy, and more research to delineate an effective dose and the potential interaction of seasonal exposure to ultraviolet light is warranted.     

Calcium-activated tenderization of strip loin, top sirloin, and top round steaks in diverse genotypes of cattle

Steers of known percentage Brahman (B) and Angus (A) breeding (100% A, n = 6; F1 B x A, n = 6; and 100% B, n = 6) were used to determine the effect of calcium chloride injection on the calpain proteinase system and meat tenderness. The steers were slaughtered in six replications (at either 9 or 14 mm of backfat, determined ultrasonically), with each breed type represented. Calpains and calpastatin activities were measured on fresh, prerigor longissimus muscle samples. Carcass data were collected after a 24-h chill, and the short loin (IMPS #180), top sirloin (IMPS #184), and top round (IMPS #168) were removed from both sides of each carcass. The cuts from the right side were then injected at 5% (wt/wt) with CaCl2 solution (2.2%). Longissimus muscle calpain and calpastatin activities were also measured at 48 h postmortem from the injected and control sides of each carcass. Warner-Bratzler shear force was measured on steaks from the three subprimals aged 1, 2, 5, 15, or 31 d. Marbling scores and USDA quality grades were higher (P<.05) in A than in F1 B x A and B carcasses. Calpastatin activity was higher (P<.05) in muscle from B than in muscle from A and F1 B x A steers, and postmortem storage (O vs 48 h) and CaCl2 injection reduced (P<.05) the activity of the calpains and calpastatin. Strip loin and top sirloin steaks from A and F1 B x A steers were more tender (P<.05) than steaks from B steers; however, top round steak tenderness did not differ (P>.05) across breed type. Calcium injection improved strip loin and top sirloin steak tenderness, but it did not affect top round steak tenderness. Collectively, these data show that CaC12 injection can be used to improve meat tenderness, with similar responses shown in cattle containing 0, 50, and 100% B inheritance. However, even with CaCl2 injection, B steaks are less tender than their A and F1 B x A counterparts.