Biomedical subjects

L V Cundiff

Publications and source records attributed to L V Cundiff.

At least 19 recordsLinked to original sources

PubMed1996

Prediction of breeding values for tenderness of market animals from measurements on bulls.

Data were tenderness measures on steaks from 237 bulls (Group II) slaughtered after producing freezable semen and on 1,431 related steers and heifers (market animals, Group I) from Angus, Hereford, Pinzgauer, Brahman, and Sahiwal crosses from the Germ Plasm Evaluation project at the U.S. Meat Animal Research Center. Tenderness was assessed through Warner-Bratzler Shear Force (SF), taste panel tenderness (TPT), marbling score (MS), and myofibrillar fragmentation index (MFI). For all traits, as fraction Bos indicus inheritance increased, implied tenderness decreased. Heritability estimates were generally not significantly different from zero. Genetic correlations generally indicated favorable associations among the traits. The range in predicted breeding values of bulls for market animal tenderness was small and from -.34 to .32 kg for market animal shear force. Because of low estimates of heritability for SF or TPT, results from this experiment indicate that selection based on tenderness of steaks sampled from intact or late castrate males slaughtered following collection of freezable quality semen would not be very effective in improving average tenderness of steaks from steers of heifer progeny. If a mean of heritability estimates reported in the literature of .27 for shear value was assumed for market steer and heifer progeny instead of .02 as found in the present study, then selection based on estimates of shear force in young bulls would be relatively more effective in improving shear force of market progeny.

Animals↗

PubMed1996

Characterization of biological types of cattle (Cycle IV): carcass traits and longissimus palatability.

Carcass and longissimus thoracis palatability traits from 888 steers obtained from mating Hereford and Angus cows to Hereford or Angus (HA), Charolais (Ch), Gelbvieh (Gb), Pinzgauer (Pz), Shorthorn (Sh), Galloway (Gw), Longhorn (Lh), Nellore (Ne), Piedmontese (Pm), and Salers (Sa) sires were compared. Data were adjusted to constant age (426 d), carcass weight (324 kg), fat thickness (1.2 cm), fat trim percentage (23%), and marbling (small00) end points. At a constant age of 426 d, carcasses from Ch steers were heaviest (P < .05) and Gw and Lh carcasses were lightest (P < .05). Adjusted fat thickness was greatest (P < .05) on carcasses from HA and least (P < .05) on carcasses from Ch, Gb, Lh, and Pm steers. USDA numerical yield grades were lowest (P < .05) for carcasses from Pm and highest (P < .05) for carcasses from HA, Ne, and Sh steers. Marbling scores were highest (P < .05) for carcasses from HA, Pz, and Sh and lowest (P < .05) for carcasses from Ch, Ne, and Pm steers. Longissimus thoracis from Pz had a lower (P < .05) shear force than that from all other breeds except HA, Gb, and Pm. Longissimus thoracis of carcasses from Ne steers was least (P < .05) tender. Adjustment of traits to various end points resulted in some changes in sire breed differences depending on the end point and the trait being considered but had little effect on palatability traits. Carcasses from Pm-sired steers provided the most desirable combination of carcass and longissimus palatability traits.

Analysis of Variance↗

PubMed1996

Effects of twinning on dystocia, calf survival, calf growth, carcass traits, and cow productivity.

This paper reports results from a long-term experiment with a primary objective to increase twinning rate in cattle at the Roman L. Hruska U.S. Meat Animal Research Center. Survival of singles was 13% higher (P < .01) than that of twins at birth, and the difference in survival in favor of singles was of similar magnitude at 72 h (12.9%, P < .01), 150 d (14.8%, P < .01), and 200 d (15.2%, P < .01). Survival of calves with no dystocia was higher than survival of calves with dystocia: 8.6% (P < .01) at birth, 10.8% (P < .01) at 72 h, 12% (P < .01) at 150 d, and 12.2% (P < .01) at 200 d. The effect of dystocia on survival was greater (P < .01) in twins than in singles at birth and at 72 h. Least squares means for dystocia were 20.4% in singles compared with 42.2% in twins. Most of the dystocia in singles resulted from a traction requirement (84.7%) of normal presentations, whereas most of the dystocia in twins (77.8%) resulted from malpresentations, with 59.2% of the malpresentations accompanied with a requirement for traction. Survival in singles ranged from 10.7% to 15.3% greater than in twins at different ages when there was no requirement for assistance in either singles or twins. Calves born as singles were 8.8 kg heavier (P < .01) at birth and 28 kg heavier (P < .01) at 200 d than calves born and reared as twins. Calf weight produced per cow calving was 53.1%, 54.7%, and 58.4% greater (P < .01) at birth, 150 d, and 200 d, respectively, in cows producing twins than in cows producing singles. Cows producing twins had 65.2% more (P < .01) live calves at 200 d than cows producing singles. Single male calves gained 74 g more per day than twin males from birth to 200 d, 45 g more (P < .01) per day from 200 d to slaughter and 57 g more (P < .01) per day from birth to slaughter. Differences between twin and single males in carcass traits were small. A sample of steers from the Twinning Project gained significantly faster and produced significantly more desirable carcasses than a sample of steers from a high performance reference population. Freemartins did not differ (P < .05) from normal females in growth traits, but freemartins had higher (P < .05) scores for marbling with a higher percentage (P < .05) of USDA Choice or better quality grade carcasses and lower estimated percentage retail product.

Analysis of Variance↗

PubMed1995

Prediction of genetic values of sires for growth traits of crossbred cattle using a multivariate animal model with heterogeneous variances.

The purpose of this study was to evaluate the effect of adjusting for heterogeneous variances across breed groups on prediction of breeding values (PBV) of selected sires and on breed of sire effects. Data on weights at birth (BWT), 200 d (WW), and 365 d (YW) of purebred and crossbred calves from matings of Angus (A), Hereford (H), Polled Hereford, Charolais, Shorthorn, Simmental, Limousin, Maine-Anjou, Chianina, Gelbvieh, Tarentaise, and Salers Bulls to A and H cows were used. Calf performance in H and A dams was treated as a different trait. Models compared included fixed birth year, cow age, and sex classes and crossbreeding effect as a covariate; random direct and maternal genetic and permanent environmental effects were also included, but their variance structure was different. Model I assumed homogeneous variances across breed groups. Model II accounted for heterogeneous variances. Sires were ranked based on PBV from each model, and means of PBV of selected sires were calculated based on Model II. Differences between mean PBV were small for BWT, intermediate for WW, and larger for YW. Differences in PBV of selected sires increased as selection intensity increased, but only for WW and YW. Large differences in mean PBV of selected sires between maternal environments (H vs A) were observed for WW and YW for various sire breeds. Means of PBV of selected sires based on Model II exceeded those based on Model I by 6 to 16 kg of YW for various selection intensities and maternal environments. Estimates of breed of sire effects from Model I or II were similar for BWT and WW, but large differences were found for YW. Results indicate that some additional economic returns may be gained by commercial producers if sires are chosen across breeds based on predicted genetic values computed with models accounting for heterogeneous variances.

Aging↗

PubMed1995

Direct and maternal genetic responses to selection for weaning or yearling weight or for yearling weight and muscle score in Hereford cattle.

An experiment involving crosses among selection and control lines was conducted to partition direct and maternal additive genetic response to 20 yr of selection for 1) weaning weight (WWL), 2) yearling weight (YWL), and 3) an index of yearling weight and muscle score (IXL). Maternal response was estimated from reciprocal crosses among unselected sires and dams of control (CTL) and the selection lines. An Angus line was added to increase the number of reciprocal cross comparisons. Direct responses of WWL, YWL, and IXL linebreds compared with CTL were significant for all traits. Maternal genetic responses were much smaller than direct responses. Direct response in birth weight was largest for YWL, followed by WWL and IXL. Maternal effect of IXL on birth weight was larger and that of WWL and YWL was smaller than CTL. Direct responses in weaning weight did not differ greatly among selection lines; maternal response was greater for IXL than for WWL, which was selected for this trait, and response was negative for YWL. Responses in maternal effects on final weight were much reduced in Hereford crosses because of a negative relation between maternal responses in pre- and postweaning gains, especially in YWL and IXL. However, in Angus crosses, a positive association between pre- and postweaning gains increased maternal responses in final weight. Direct response for postweaning gain was greater in IXL than in YWL of WWL in Hereford crosses. In Angus crosses, YWL had larger direct responses for birth weight, preweaning gain, and postweaning gain than in other lines. The direct response for muscle score from selection in IXL, which was selected for muscle score and yearling weight, was greater than in other lines; maternal response was not important. The greatest gain in final weight was obtained when selection resulted in a favorable change in the total of direct and maternal effects pre- and postweaning, which in this experiment was provided by including a muscle score along with yearling weight as selection criteria.

Aging↗

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

Growth, digestive capability, carcass, and meat characteristics of Bison bison, Bos taurus, and Bos x Bison.

Three experiments involving 39 Bos taurus, 14 Bison bison, and 20 Bos x Bison fed diets differing in proportions of roughage and concentrate to evaluate growth, digestive capability, carcass, and meat characteristics are reported. Bos taurus consumed more (P < .05) feed per day and gained more (P < .05) rapidly than bison or Bos x Bison except during a period of extremely cold weather. Efficiency of gain was similar for all species types. There was no tendency for bison or Bos x Bison to gain more than Bos taurus on the higher-roughage diets. Bison and Bos x Bison had higher (P < .10 to .01) digestion coefficients for all components evaluated (i.e., DM, CP, GE, NDF,hemicellulose, and cellulose). Species x diet interactions were not significant, indicating that the higher digestion coefficients of bison were not specific to high-roughage diets. Bison and their hybrids had more (P < .05) lean meat and less (P < .01) fat trim in all wholesale cuts except the chuck and rib cuts. Fat thickness at the 12th rib of bison was higher (P < .01) than that of Bos taurus because most of the carcass fat of bison is located over the thoracic area. Bison and Bos x Bison had higher (P < .01) dressing percentages and a lower (P < .01) proportion of their carcass in the hindquarter than Bos taurus. Shear force and sensory tenderness scores indicated bison were more (P < .05) tender and had a flavor different (P < .01) from that of Bos taurus. Bison and Bos x Bison had more (P < .01) cholesterol in the longissimus muscle and less (P < .05) in the subcutaneous fat than Bos taurus. Bison had a lower (P < .01) percentage of white and higher percentage of intermediate muscle fibers than Bos taurus with essentially no difference in percentage of red fibers.

Animals↗

PubMed1995

Real-time ultrasonic measurement of fat thickness and longissimus muscle area: I. Description of age and weight effects.

Serial ultrasonic measures of fat thickness (FTU) and longissimus muscle area (LMU) were taken on 180 feedlot steers representing 11 sire-breed groups at two 60-d intervals. Cattle then were slaughtered in four groups of 45 at 21-d intervals with ultrasonic measures taken at each interval. Analyses of variance indicated weight (WT) effects (P < .001) for all FTU measures and many of the LMU measures. Age was a source of variation (P < .05) for FTU and LMU over the first five measurement dates. Sire-breed (SBD) effects (P < .001) were prevalent for all FTU estimates and early LMU predictions. Some dam line and SBD x dam line interactions were detected (P < .1) for the FTU and LMU estimates. Age effects were described quadratically (P < .001) when FTU and LMU were regressed on age (R2 = 47 and 68%, respectively). When FTU and LMU were regressed on WT, effects were described quadratically (P < .001) with R2 values of 46 and 72%, respectively. Animals then were assigned to one of four biological types (BT) based on percentage of retail product (0-mm fat trim) using discriminant cluster analysis. Within BT, ultrasonic variables were regressed on age. Quadratic effects (P < .01) were detected for both FTU and LMU. Weight also contributed to variation observed in both ultrasonically measured variables for all BT (P < .001). These data indicate that changes in fat and muscle size as affected by age and weight are detectable using serially collected ultrasound measures. Furthermore, the age and weight relationships of predicted FTA and LMA varied across the four biological types. This suggests a need for derivation of biological type-specific age and(or) weight adjustment equations for cattle evaluation purposes.

Adipose Tissue↗

PubMed1995

Real-time ultrasonic measurement of fat thickness and longissimus muscle area: II. Relationship between real-time ultrasound measures and carcass retail yield.

Feedlot steers (n = 180) representing 11 sire-breed groups were ultrasonically measured for fat thickness (FTU) and longissimus muscle area (LMU) at two 60-d intervals during the feeding period and four 21-d intervals corresponding to serial slaughter dates to predict carcass retail yield parameters. Two fat trim levels, 8 and 0 mm, were used to calculate percentage of trimmable fat (FAT8P and FAT0P) and retail product percentage (RPD8P and RPD0P) for each carcass. Regression techniques were used to evaluate best-fit equations that explained variation in retail product components. When FAT8P, FAT0P, RPD8P, and RPD0P were regressed on USDA yield grade (YG), R2 values ranged from 75 to 76% (P < .001). Comparatively, when live animal predictors of YG components (FTU, LMU, and final live weight) were used as the independent variables, equations predicting retail yield had R2 values of 61 to 65% (P < .01). Equations using final FTU as the independent variable explained 58 to 64% (P < .001) of the variation in FAT8P, FAT0P, RPD8P, and RPD0P. Equations with FTU, LMU, and either WT, AGE, marbling, or quality grade resulted in R2 values similar to those with only FTU, indicating the strong influence of fat on retail yields. These results indicate that ultrasonic predictors explained about 10% less variation in retail product percentage than did carcass measures.

Adipose Tissue↗

PubMed1995

Genetic and phenotypic (co)variances for growth and carcass traits of purebred and composite populations of beef cattle.

Least squares means, genetic (sigma g), and phenotypic (sigma p) standard deviations, and phenotypic coefficients of variation (CV) were estimated on an age-constant basis for growth, carcass, and meat traits of castrate males from 12 breed groups combined, for 9 purebreds combined, and for the F3 generation of three composite populations combined to which the nine purebreds contributed. Also, heritabilities (h2) and genetic (rg) and phenotypic (rp) correlations were estimated among growth, carcass, and meat traits for all breed groups combined involving 1,594 individuals that were the progeny of 306 sires (214 purebred and 92 composites). Coefficients of variation and sigma g generally were similar for composites and contributing purebreds for growth and size-related traits. For traits relating to carcass composition and meat quality, means, sigma p, or CV for composites and contributing purebreds generally were similar. Generally, estimates of sigma g and h2 were similar among all breed groups combined, contributing purebreds combined, and composites combined. Generally, rg were high among all measures of carcass fat, indicating major difficulty in achieving a high percentage of retail product simultaneously with a high fat content of the longissimus muscle that is required for carcass quality grade. Generally, rp were of smaller magnitude than rg. All rp of marbling score or percentage of ether-extracted fat in the longissimus muscle with all end-use properties relating to palatability including shear force, and sensory evaluation of tenderness, juiciness, and flavor were below .30.

Animals↗

PubMed1995

Genetic and phenotypic (co)variances for production traits of intact male populations of purebred and composite beef cattle.

Least squares means, genetic (sigma g) and phenotypic (sigma p) standard deviations, and phenotypic coefficients of variation (CV) were estimated for growth traits of intact males from 12 breed groups combined, for nine purebreds combined, and for the F1, F2, F3, and F4 generations of three composite populations to which the nine purebreds contributed. Heritabilities (h2) and genetic (rg) and phenotypic (rp) correlations were estimated for growth traits, calving difficulty of calves with dams of different ages, and gestation length. Coefficients of variation and sigma g generally were similar for composites and contributing purebreds. Generally, estimates of h2 were similar for all breed groups combined, contributing purebreds combined, and composites combined. Estimates of h2 for calving difficulty were higher for calves with 2-yr-old dams than for calves with dams > or = 3 yr old and were sufficiently high (.27 and .31) to be a useful selection criterion for reducing calving difficulty. Mean h2 pooled within all breed groups ranged from .35 for 200-d weight and 368-d weight to .48 for 368-d height. Estimates of h2 for subjective scores of anatomical traits were only slightly lower than those for growth and size traits. The h2 of scrotal circumference (.43) was similar to those for growth and size traits. Genetic correlations between birth weight and calving difficulty were similar for 1) calves with dams of all ages, 2) calves with 2-yr-old dams, and 3) calves with dams > or = 3 yr old.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

PubMed1995

Genetic and phenotypic (co)variances for production traits of female populations of purebred and composite beef cattle.

Least squares means, genetic and phenotypic standard deviations, and phenotypic coefficients of variation were estimated for growth, size, condition score, age at puberty, gestation length, and calving difficulty as traits of individual females from 12 breed groups combined, for nine purebreds combined, and for the F1, F2, and F3 generations of three composite populations to which the nine purebreds contributed. Heritabilities and genetic and phenotypic correlations were estimated for growth and size traits, age at puberty, gestation length, and calving difficulty of calves with dams of different ages. Coefficients of variation and genetic standard deviations were similar for composites and contributing purebreds for the traits evaluated. Generally, estimates of heritability were similar for all breed groups combined, contributing purebreds combined, and composites combined. Estimates of heritability for calving difficulty were higher for calves with 2-yr-old dams than for calves with dams > or = 3 yr old and were sufficiently high (.33 and .26) to be a useful selection criterion for reducing calving difficulty. Estimate of heritability for age at puberty was .31 and for gestation length was .45. The rg between birth weight and calving difficulty score was higher for calves with 2-yr-old dams (.59) than for calves with dams > or = 3 yr old (.44). The higher genetic correlation between birth weight and calving difficulty score (.59) in calves with 2-yr-old dams than between birth weight and 368-d weight (.33) suggests opportunity to reduce calving difficulty by reducing birth weight while maintaining 368-d weight.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

PubMed1995

Heterogeneity of variance by sire breed, sex, and dam breed in 200- and 365-day weights of beef cattle from a top cross experiment.

The nature of the heterogeneity of variance for 200- and 365-d weights by sex, sire breed, and dam breed subclasses was studied. Data consisted of records for weaning (n = 7,829) and yearling (n = 7,367) weights of progeny from 673 and 672 sires, respectively, from 22 breeds that have been evaluated in the Germ Plasm Evaluation Program at the U.S. Meat Animal Research Center, Clay Center, NE. Sires were mated to Hereford and Angus cows. Each trait was analyzed separately. Three studies were undertaken separately to investigate heterogeneity due to the different factors (i.e., sire breed, sex, or dam breed). Only data from seven sire breeds were used to study the factor sire breed, but all data (22 sire breeds) were used to study the factors sex and dam breed. In each study, three sire and dam models with records of animals of the four sex x dam breed combinations considered different traits and with the same model equation, but covariance structures for random effects (sires, dams, and residuals) of increasing generality were fitted. First, (co)variances across subclasses were assumed equal. Second, correlations and fractions of phenotypic variance were assumed equal but phenotypic variance differed by sire breed, sex, or dam breed as appropriate. Third, variances and covariances were different for each subclass of the factor under study. Variance components were estimated by derivative-free REML. Models for each trait and each factor were compared through likelihood ratio tests. For both traits, variances differed (P < .02) in scale, but not as fractions of phenotypic variance (P > .10), by sire breed and sex subclasses. Variances were not different (P > .10) by dam breed subclasses, either in scale or as fractions of phenotypic variance. Estimates of correlations among genetic effects on weights of calves from different sex-dam breed subclasses were at least .85. Across all sex, sire breed, and dam breed subclasses, pooled estimates of sire and dam variances as fractions of phenotypic variance were, respectively, .06 and .39 for weaning weight and .11 and .24 for yearling weight. The conclusion is that the assumption of equal phenotypic variances among sire breeds and between sexes may not be appropriate in genetic evaluations.

Algorithms↗

PubMed1995

Effect of accounting for different phenotypic variances by sire breed and sex on selection of sires based on expected progeny differences for 200- and 365-day weights.

The effects of accounting for different phenotypic variances according to sire breed and sex subclasses on estimation of sire breed effects and prediction of expected progeny differences of sires mated to Hereford and Angus cows were investigated. Data consisted of 6,977 and 6,530 records of 200-d (weaning) and 365-d (yearling) weights, respectively, of F1 calves sired by bulls (662 and 661, respectively) of 23 breeds that have been evaluated in the Germ Plasm Evaluation Program at the U.S. Meat Animal Research Center, Clay Center, NE. Models compared included fixed effects of genetic group of sire (samples of sires evaluated at different times), dam breed, sex, birth year of calf and age of dam, plus sire within genetic group and dam within dam breed as random effects. Variance structures were different: Model I assumed homogeneous variances across sire breed-sex subclasses; Model II accounted for differences in phenotypic variance by sire breed and sex subclasses. Differences between estimates of sire group effects obtained with the two models were not significant for either trait. Product-moment and rank correlations between expected progeny differences obtained with Model I and Model II were greater than .93 when computed within each group and .99 or larger when computed across breeds. There were slight changes in the numbers of sires contributed by different breeds to the proportions selected across breeds under different selection intensities when sires were ranked with the two models. However, differences between means predicted under Model II were small when sires were ranked and selected based on the two models. Changes in standard errors of prediction for expected progeny differences and standard errors for estimates of breed effects obtained when adjusting for differences of phenotypic variances, compared to not adjusting, were proportional to the ratios of the phenotypic standard deviations of the sire breeds to the common phenotypic standard deviation.

Animals↗

PubMed1994

Effect of marbling degree on beef palatability in Bos taurus and Bos indicus cattle.

This study was designed to evaluate the relationship between marbling score and breed-type (Bos taurus vs < or = 1/4 Bos indicus) on palatability of cooked beef. One thousand six hundred sixty-seven steers and heifers (1,337 Bos taurus and 330 Bos indicus x Bos taurus crosses) that had been managed and fed alike were used. Shear force and tenderness rating indicated that meat from Bos indicus cattle was less tender (P < .05) than meat from Bos taurus cattle, regardless of marbling score. Meat from Bos indicus cattle decreased (P < .05) in shear force as marbling increased from Traces to Small. Meat from Bos taurus cattle also decreased (P < .05) in shear force as marbling increased from Traces to Small, but Small was not different (P > .05) from Modest or Moderate marbling. In addition, variation in shear force was lower (P < .05) in meat from Bos taurus cattle and tended to decrease as marbling increased. Meat with Modest and Moderate marbling from Bos taurus cattle was more juicy (P < .05) than meat with Traces or Slight marbling. Beef flavor intensity rating was not affected (P > .05) by marbling score in either Bos taurus or Bos indicus cattle. Percentage yield of retail product decreased (P < .05) as marbling score increased but was not related (P > .05) to shear force or tenderness rating.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

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

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↗