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1.
The objective of this study was to estimate parameters required for genetic evaluation of Simmental carcass merit using carcass and live animal data. Carcass weight, fat thickness, longissimus muscle area, and marbling score were available from 5,750 steers and 1,504 heifers sired by Simmental bulls. Additionally, yearling ultrasound measurements of fat thickness, longissimus muscle area, and estimated percentage of intramuscular fat were available on Simmental bulls (n = 3,409) and heifers (n = 1,503). An extended pedigree was used to construct the relationship matrix (n = 23,968) linking bulls and heifers with ultrasound data to steers and heifers with carcass data. All data were obtained from the American Simmental Association. No animal had both ultrasound and carcass data. Using an animal model and treating corresponding ultrasound and carcass traits separately, genetic parameters were estimated using restricted maximum likelihood. Heritability estimates for carcass traits were 0.48 +/- 0.06, 0.35 +/- 0.05, 0.46 +/- 0.05, and 0.54 +/- 0.05 for carcass weight, fat thickness, longissimus muscle area, and marbling score, respectively. Heritability estimates for bull (heifer) ultrasound traits were 0.53 +/- 0.07 (0.69 +/- 0.09), 0.37 +/- 0.06 (0.51 +/- 0.09), and 0.47 +/- 0.06 (0.52 +/- 0.09) for fat thickness, longissimus muscle area, and intramuscular fat percentage, respectively. Heritability of weight at scan was 0.47 +/- 0.05. Using a bivariate weight model including scan weight of bulls and heifers with carcass weight of slaughter animals, a genetic correlation of 0.77 +/- 0.10 was obtained. Models for fat thickness, longissimus muscle area, and marbling score were each trivariate, including ultrasound measurements on yearling bulls and heifers, and corresponding carcass traits of slaughter animals. Genetic correlations of carcass fat thickness with bull and heifer ultrasound fat were 0.79 +/- 0.13 and 0.83 +/- 0.12, respectively. Genetic correlations of carcass longissimus muscle area with bull and heifer ultrasound longissimus muscle area were 0.80 +/- 0.11 and 0.54 +/- 0.12, respectively. Genetic correlations of carcass marbling score with bull and heifer ultrasound intramuscular fat percentage were 0.74 +/- 0.11 and 0.69 +/- 0.13, respectively. These results provide the parameter estimates necessary for genetic evaluation of Simmental carcass merit using both data from steer and heifer carcasses, and their ultrasound indicators on yearling bulls and heifers.  相似文献   

2.
Live weight and ultrasound measures of fat thickness and longissimus muscle area were available on 404 yearling bulls and 514 heifers, and carcass measures of weight, longissimus muscle area, and fat thickness were available on 235 steers. Breeding values were initially estimated for carcass weight, longissimus muscle area, and fat thickness using only steer carcass data. Breeding values were also estimated for weight and ultrasound muscle area and fat thickness using live animal data from bulls and heifers, with traits considered sex-specific. The combination of live animal and carcass data were also used to estimate breeding values in a full animal model. Breeding values from the carcass model were less accurate and distributed more closely around zero than those from the live data model, which could at least partially be explained by differences in relative amounts of data and in phenotypic mean and heritability. Adding live animal data to evaluation models increased the average accuracy of carcass trait breeding values 91, 75, and 51% for carcass weight, longissimus muscle area, and fat thickness, respectively. Rank correlations between breeding values estimated with carcass vs live animal data were low to moderate, ranging from 0.16 to 0.43. Significant rank changes were noted when breeding values for similar traits were estimated exclusively with live animal vs carcass data. Carcass trait breeding values estimated with both live animal and carcass data were most accurate, and rank correlations reflected the relative contribution of carcass data and their live animal indicators. The addition of live animal data to genetic evaluation of carcass traits resulted in the most significant carcass trait breeding value accuracy increases for young replacements that had not yet produced progeny with carcass data.  相似文献   

3.
Carcass measurements for weight, longissimus muscle area, 12-13th-rib fat thickness, and marbling score, as well as for live animal measurements of weight at the time of ultrasound, ultrasound longissimus muscle area, ultrasound 12-13th-rib fat thickness, and ultrasound-predicted percentage ether extract were taken on 2,855 Angus steers. The average ages for steers at the time of ultrasound and at slaughter were 391 and 443 d, respectively. Genetic and environmental parameters were estimated for all eight traits in a multivariate animal model. In addition to a random animal effect, the model included a fixed effect for contemporary group and a covariate for measurement age. Heritabilities for carcass weight, carcass longissimus muscle area, carcass fat thickness, carcass marbling score, ultrasound weight, ultrasound longissimus muscle area, ultrasound fat thickness, and ultrasound-predicted percentage ether extract were 0.48, 0.45, 0.35, 0.42, 0.55, 0.29, 0.39, and 0.51, respectively. Genetic correlations between carcass and ultrasound longissimus muscle area, carcass and ultrasound fat thickness, carcass marbling score and ultrasound-predicted percentage ether extract, and carcass and ultrasound weight were 0.69, 0.82, 0.90, and 0.96, respectively. Additional estimates were derived from a six-trait multivariate animal model, which included all traits except those pertaining to weight. This model included a random animal effect, a fixed effect for contemporary group, as well as covariates for both measurement age and weight. Heritabilities for carcass longissimus muscle area, carcass fat thickness, carcass marbling score, ultrasound longissimus muscle area, ultrasound fat thickness, and ultrasound-predicted percentage ether extract were 0.36, 0.39, 0.40, 0.17, 0.38, and 0.49, respectively. Genetic correlations between carcass and ultrasound longissimus muscle area, carcass and ultrasound fat thickness, and carcass marbling and ultrasound-predicted percentage ether extract were 0.58, 0.86, and 0.94, respectively. The high, positive genetic correlations between carcass and the corresponding real-time ultrasound traits indicate that real-time ultrasound imaging is an alternative to carcass data collection in carcass progeny testing programs.  相似文献   

4.
Heifer and steer progeny of 2-yr-old first-cross (F1) heifers and 3- to 6-yr-old F1 cows, from Hereford dams and five sire breeds, were evaluated for postweaning feedlot growth and carcass composition. Breeds of sire of dam were Angus (A), Red Poll (RP), Tarentaise (T), Simmental (Sm), and Pinzgauer (P). Calves from 2-yr-old heifers were sired by Shorthorn, and calves from 3- to 6-yr-old dams were sired by Charolais. Breed of sire of dam was significant (P less than .05 to P less than .01) for total gain and final weight for female progeny from 2-yr-old dams. At all weights, Sm, P, and T ranked above A and RP. Progeny of A, P, Sm, and T F1 2-yr-old dams were not significantly different but were higher (P less than .05) than RP heifers in total feedlot gain. Breed of sire of dam was significant (P less than .05) for carcass weight and longissimus muscle area; T ranked highest and RP lowest. Breed was not significant for any growth traits of steer progeny of 2-yr-old dams. Breed was significant for marbling score; A ranked highest and exceeded (P less than .01) both RP and Sm steers. Breed was significant (P less than .05) for most growth traits in the heifer progeny of the 3- to 6-yr-old dams bred to Charolais sires. Heifer calves of the Sm group were heavier (P less than .05) than all other groups for most weights and total gain. For total gain, P and T were intermediate and A and RP lowest. For heifer carcass traits from 3- to 6-yr-old dams, breed was significant (P less than .05 to P less than .01) for carcass weight, longissimus muscle area, percentage of cutability, and estimated kidney, heart, and pelvic fat. Heifers from Sm-sired dams were heavier (P less than .05) than those from all other groups but ranked second to heifers from P for percentage of cutability. Marbling scores of RP heifer carcasses ranked highest of all groups. Breed was not significant (P greater than .05) for any of the weights or gains in steer progeny of 3- to 6-yr-old dams; however, the Sm and P groups ranked above A and RP for all feedlot test weights.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

5.
Adjustment factors to allow comparison of EPD from several breed associations for birth, weaning, and yearling weights have been available for more than 10 yr. This paper describes steps to calculate adjustment factors for EPD for 4 carcass traits: marbling score, fat thickness, ribeye area, and retail product percentage. The required information is the same as for the weight traits: 1) breed of sire solutions based on measurements on progeny at the US Meat Animal Research Center (USMARC) that have sires with breed association EPD, 2) mean EPD of sires weighted by number of progeny at USMARC (USMARC progeny not included in breed association EPD), and 3) mean EPD of nonparents from breed associations (defined as animals born 2 yr prior to calculation of EPD). Records at USM-ARC are adjusted to 100% heterozygosity because the purpose of the adjustment factors is to allow prediction of performance of progeny of sires mated to other breeds of dam. A critical step is to adjust breed of sire solutions, which are based on an earlier sample of sires, to the equivalent of a sample from a more recent nonparent group using the difference between mean EPD from information sources 2) and 3). The difference is multiplied by the coefficient of regression of USMARC progeny on EPD of their sires. With weight traits, these coefficients are not greatly different from unity. With the carcass traits, 2 sets of coefficients can be used depending on whether the EPD are based on carcass or ultrasound measurements. The regression coefficients also reflect differences in conditions for USMARC progeny (all steers) and factors associated with breed association EPD. Only for marbling score and ribeye area were any estimates of the regression coefficients near unity. For other traits, the coefficients ranged from 1.65 to 2.82. The solutions for breed of sire, differences in mean EPD, and regression coefficients are then used to calculate adjustment factors for EPD of 11 breeds including the arbitrary base breed, Angus.  相似文献   

6.
Angus bulls (n = 20) from three pure-bred herds in Georgia were acquired to determine the impact of selecting sires based on phenotypic yearling ultrasound intramuscular fat percentage (UIMF) or UIMF EPD on marbling score of steer progeny. Each year in each herd, pairs of bulls were selected to create large differences based on their age adjusted phenotypic yearling UIMF measurements. The average UIMF, weighted by number of progeny per sire, was 3.75% (SD = 1.10%) and 1.70% (SD = 0.53%) for high UIMF (HU) and low UIMF (LU) bulls, respectively. All available ultrasound measurements collected in the purebred co-operator herds were combined with other ultrasound records collected by the American Angus Association for the computation of genetic values for ultrasound fat thickness, ribeye area, and intramuscular fat percentage. Each year bulls were randomly mated to 14 to 30 commercial Angus females. Carcass weight, fat thickness at the 12th rib, ribeye area at the 12th rib, marbling score, yield grade, and quality-grade measurements were collected on 188 steer progeny. Carcass data were linearly adjusted to 480 d of age at slaughter. Steer progeny sired by HU bulls had higher age-adjusted marbling score and quality grade (P < 0.05), and smaller age-adjusted ribeye area (P < 0.05) than steer progeny sired by LU bulls. No significant differences between phenotypic UIMF lines were found for age-adjusted fat thickness (P = 0.84) and yield grade (P = 0.33) in the steer progeny. The regression of age-adjusted carcass marbling score and quality grade of the steer progeny on ultrasound intramuscular fat percentage EPD of the sires produced highly significant regression coefficients of 90.50 and 49.20, respectively. Thus, yearling Angus bulls selected for high-phenotypic UIMF and UIMF EPD can be expected to produce steer progeny with significantly higher amounts of marbling and quality grade. It also appears that marbling can be increased without corresponding increases in external fat thickness and yield grade.  相似文献   

7.
Carcass and live-animal measures from 1,029 cattle were collected at the Iowa State University Rhodes and McNay research farms over a 6-yr period. Data were from bull, heifer, and steer progeny of composite, Angus, and Simmental sires mated to three composite lines of dams. The objectives of this study were to estimate genetic parameters for carcass traits, to evaluate effects of sex and breed of sire on growth models (curves), and to suggest a strategy to adjust serially measured data to a constant age end point. Estimation of genetic parameters using a three-trait mixed model showed differences between bulls and steers in estimates of h2 and genetic correlations. Heritability for carcass weight, percentage of retail product, retail product weight, fat thickness, and longissimus muscle area from bull data were .43, .04, .46, .05, and .21, respectively. The corresponding values for steer data were in order of .32, .24, .40, .42, and .07, respectively. Analysis of serially measured fat thickness, longissimus muscle area, body weight, hip height, and ultrasound percentage of intramuscular fat using a repeated measures model showed a limitation in the use of growth models based on pooled data. In further evaluation of regression parameters using a linear mixed model analysis, sex and breed of sire showed an important (P < .05) effect on intercept and slope values. Regression of serially measured traits on age within animal showed a relatively larger R2 (62 to 98%) and a smaller root mean square error (RMSE, .09 to 8.85) as compared with R2 (0 to 58%) and RMSE (.31 to 67.9) values when the same model was used on pooled data. We concluded that regression parameters from a within-animal regression of a serially measured trait on age, averaged by sex and breed, are the best choice in describing growth and adjusting data to a constant age end point.  相似文献   

8.
Growth and carcass measurements were made on 2,411 Hereford steers slaughtered at a constant weight from a designed reference sire program involving 137 sires. A second data set consisted of ultrasound measures of backfat (USFAT) and longissimus muscle area (USREA) from 3,482 yearling Hereford cattle representing 441 sires. Restricted maximum likelihood procedures were used to estimate genetic parameters among carcass traits and live animal weight traits from these two separate data sets. Heritability estimates for the slaughter weight constant steer carcass backfat (FAT) and longissimus muscle area (REA) were .49 and .46, respectively. In addition, FAT had a negative genetic correlation with REA (-.37), weaning weight (-.28), and yearling weight (-.13) but positive with marbling (.19) and carcass weight (.36). Marbling was moderately heritable (.35) and highly correlated with total postweaning average daily gain (.54) and feedlot relative growth rate (.62). Heritability estimates for weight constant USFAT and USREA were .26 and .25, respectively. The genetic correlation between weight constant USFAT and USREA was positive (.39), indicating that in these young animals USFAT does not seem to be an indication of maturity. Mean USFAT measures and variability were small (.48 +/- .17 cm, n = 3,482). Results indicate that carcass fat on slaughter steers and ultrasound measures of backfat on young breeding animals may have different relationships with growth and muscling. These relationships need to be explored before wide scale selection based on ultrasound is implemented.  相似文献   

9.
In order to estimate genetic parameters, abattoir carcass data on 1,713 Angus and 1,007 Hereford steers and heifers were combined with yearling live-animal ultrasound measurements on 8,196 Angus and 3,405 Hereford individuals from seedstock herds. Abattoir measures included carcass weight (CWT), percentage of retail beefyield (RBY), near-infrared measured intramuscular fat percentage (CIMF), preslaughter scanned eye muscle area (CEMA), and subcutaneous fat depth at the 12th rib (CRIB) and at the P8 site (CP8). Ultrasound scans on yearling animals included 12th-rib fat depth (SRIB), rump fat depth at the P8 site (SP8), eye muscle area (SEMA), and percentage of intramuscular fat (SIMF). Records on CWT were adjusted to 650-d slaughter age, and the remaining abattoir traits were adjusted to 300-kg CWT. Scan data were analyzed treating records on males and females as different traits. Multivariate analyses were performed on a variety of trait combinations using animal model and REML algorithm. Heritability (h2) estimates for CWT, RBY, CIMF, CP8, CRIB, and CEMA were .31, .68, .43, .44, .28, and .26, respectively, for Angus and .54, .36, .36, .08, .27, .38, respectively, for Hereford. Pooled across sexes, h2 estimates for SIMF, SP8, SRIB, and SEMA were .33, .55, .51, and .42, respectively, for Angus and .20, .31, .18, and .38, respectively, for Hereford. Genetic correlations (r(g)) between the same pair of carcass traits measured at yearling through scanning and directly at the abattoir were moderate to strongly positive, suggesting that selection using yearling ultrasound measurements of seedstock cattle should result in predictable genetic improvement for abattoir carcass characteristics. Estimates of r(g) between the scanned fat measurements and RBY were negative, ranging from -.85 for Angus heifers to -.05 for Hereford heifers. Also, the estimates of r(g) between SEMA and the fat records measured at the abattoir were negative and ranged from -.94 in Hereford heifers to -.02 in Angus heifers.  相似文献   

10.
Real time ultrasound (RTU) measures of longissimus muscle area and fat depth were taken at 12 and 14 mo of age on composite bulls (n = 404) and heifers (n = 514). Carcass longissimus muscle area and fat depth, hot carcass weight, estimated percentage lean yield, marbling score, Warner-Bratzler shear force, and 7-rib dissectable seam fat and lean percentages were measured on steers (n = 235). Additive genetic variances for longissimus muscle area were 76 and 77% larger in bulls at 12 and 14 mo than the corresponding estimates for heifers. Heritability estimates for longissimus muscle area were 0.61 and 0.52 in bulls and 0.49 and 0.47 in heifers at 12 and 14 mo, respectively. The genetic correlations of longissimus muscle area of bulls vs heifers were 0.61 and 0.84 at 12 and 14 mo, respectively. Genetic correlations of longissimus muscle area measured in steer carcasses were 0.71 and 0.67 with the longissimus muscle areas in bulls and heifers at 12 mo and 0.73 and 0.79 at 14 mo. Heritability estimates for fat depth were 0.50 and 0.35 in bulls and 0.44 and 0.49 in heifers at 12 and 14 mo, respectively. The genetic correlation of fat depth in bulls vs heifers at 12 mo was 0.65 and was 0.49 at 14 mo. Genetic correlations of fat depth measured in bulls at 12 and 14 mo with fat depth measured in steers at slaughter were 0.23 and 0.21, and the corresponding correlations of between heifers and steers were 0.66 and 0.86, respectively. Live weights at 12 and 14 mo were genetically equivalent (r(g) = 0.98). Genetic correlations between live weights of bulls and heifers with hot carcass weight of the steers were also high (r(g) > 0.80). Longissimus muscle area measured using RTU was positively correlated with carcass measures of longissimus muscle area, estimated percentage lean yield, and percentage lean in a 7-rib section from steers. Measures of backfat obtained using RTU were positively correlated with fat depth and dissectable seam fat from the 7-rib section of steer carcasses. Genetic correlations between measures of backfat obtained using RTU and marbling were negative but low. These results indicate that longissimus muscle area and backfat may be under sufficiently different genetic control in bulls vs heifers to warrant being treated as separate traits in genetic evaluation models. Further, traits measured using RTU in potential replacement bulls and heifers at 12 and 14 mo of age may be considered different from the corresponding carcass traits of steers.  相似文献   

11.
Carcass and growth measurements of finished crossbred steers (n = 843) and yearling ultrasound and growth measurements of purebred bulls (n = 5,654) of 11 breeds were analyzed to estimate genetic parameters. Multiple-trait restricted maximum likelihood (REML) was used to estimate heritabilities and genetic correlations between finished steer carcass measurements and yearling bull ultrasound measurements. Separate analyses were conducted to examine the effect of adjustment to three different end points: age, backfat thickness, and weight at measurement. Age-constant heritability estimates from finished steer measurements of hot carcass weight, carcass longissimus muscle area, carcass marbling score, carcass backfat, and average daily feedlot gain were 0.47, 0.45, 0.35, 0.41, and 0.30, respectively. Age-constant heritability estimates from yearling bull measurements of ultrasound longissimus muscle area, ultrasound percentage of intramuscular fat, ultrasound backfat, and average daily postweaning gain were 0.48, 0.23, 0.52, and 0.46, respectively. Similar estimates were found for backfat and weight-constant traits. Age-constant genetic correlation estimates between steer carcass longissimus muscle area and bull ultrasound longissimus muscle area, steer carcass backfat and bull ultrasound backfat, steer carcass marbling and bull ultrasound intramuscular fat, and steer average daily gain and bull average daily gain were 0.66, 0.88, 0.80, and 0.72, respectively. The strong, positive genetic correlation estimates between bull ultrasound measurements and corresponding steer carcass measurements suggest that genetic improvement for steer carcass traits can be achieved by using yearling bull ultrasound measurements as selection criteria.  相似文献   

12.
In a 4-yr study, early-weaned Simmental steers (n = 192) of known genetics were individually fed to determine genetic, performance, and carcass factors explaining variation in carcass value and profitability. Steers were weaned at 88.0 +/- 1.1 d of age and pen-fed a high-concentrate diet (108.99 dollars/t) for 84.5 +/- 0.4 d before allotment. Calves were implanted with Synovex C at weaning and successively with Synovex S (Fort Dodge Animal Health, Fort Dodge, IA) and Revalor S (Intervet, Inc., Millsboro, DE). Steers consumed a 90% concentrate diet (98.93 dollars/t), consisting primarily of coarse cracked corn and corn silage, for 249.7 +/- 0.7 d and slaughtered at 423.3 +/- 1.4 d of age. Five-year price data were collected for feedstuffs, dressed beef, and grid premiums, and discounts. Average dressed beef price was 110.67 dollars/45.4 kg. Premiums (dollars/45.4 kg) were given for Prime (5.62 dollars), Average Choice (1.50 dollars), and yield grades (YG) 1 (2.46 dollars), 2A (1.31 dollars), and 2B (1.11 dollars). Discounts (dollars/45.4 kg) were given for Standard (-16.85 dollars), Select (-8.90 dollars), and YG 3A (-0.12 dollars), 3B (-0.19 dollars), 4 (-14.16 dollars), and 5 (-19.56 dollars). Discounts were given for HCW extremes as well (409 to 431 kg, -0.64 dollars; 432 to 454 kg -11.39 dollars; > 454 kg, -19.71 dollars). Input costs included annual cow costs (327.77 dollars), veterinary/medical and labor (35 dollars per animal), feed markup (22 dollars/t), yardage (0.25 dollars/d per animal), and interest (10%). Dependent variables were carcass value and profit per steer. Independent variables were year, weaning weight EPD, yearling weight EPD, marbling EPD, DMI, ADG, G:F, HCW, calculated YG, and marbling score (MS). Carcass value was correlated (P < 0.05) with yearling weight and marbling EPD, DMI, ADG, feed efficiency, HCW, and MS. Carcass weight, MS, and YG accounted for nearly 80% of the variation in carcass value among steers, explaining 51, 10, and 8%, respectively. Profit was correlated (P < 0.05) with DMI, ADG, feed efficiency, HCW, and MS. Carcass weight, MS, YG, and DMI accounted for nearly 78% of the variation in profit among steers, explaining 21, 18, 12, and 3%, respectively. Carcass weight was the most critical factor contributing to carcass value, whereas BW and carcass quality were the primary factors affecting steer profitability. These models represent the relative importance of factors contributing to value and profitability in early-weaned Simmental steers based on historical pricing scenarios.  相似文献   

13.
A primary genomic screen for quantitative trait loci (QTL) affecting carcass and growth traits was performed by genotyping 238 microsatellite markers on 185 out of 300 total progeny from a Bos indicus x Bos taurus sire mated to Bos taurus cows. The following traits were analyzed for QTL effects: birth weight (BWT), weaning weight (WW), yearling weight (YW), hot carcass weight (HCW), dressing percentage (DP), fat thickness (FT), marbling score (MAR), longissimus muscle area (LMA), rib bone (RibB), rib fat (RibF), and rib muscle (RibM), and the predicted whole carcass traits, retail product yield (RPYD), fat trim yield (FATYD), bone yield (BOYD), retail product weight (RPWT), fat weight (FATWT), and bone weight (BOWT). Data were analyzed by generating an F-statistic profile computed at 1-cM intervals for each chromosome by the regression of phenotype on the conditional probability of receiving the Brahman allele from the sire. There was compelling evidence for a QTL allele of Brahman origin affecting an increase in RibB and a decrease in DP on chromosome 5 (BTA5). Putative QTL at or just below the threshold for genome-wide significance were as follows: an increase in RPYD and component traits on BTA2 and BTA13, an increase in LMA on BTA14, and an increase in BWT on BTA1. Results provided represent a portion of our efforts to identify and characterize QTL affecting carcass and growth traits.  相似文献   

14.
The first objective of this study was to test the ability of systems of weighing and classifying bovine carcasses used in commercial abattoirs in Ireland to provide information that can be used for the purposes of genetic evaluation of carcass weight, carcass fatness class, and carcass conformation class. Secondly, the study aimed to test whether genetic and phenotypic variances differed by breed of sire. Variance components for carcass traits were estimated for crosses between dairy cows and 8 breeds of sire commonly found in the Irish cattle population. These 8 breeds were Aberdeen Angus, Belgian Blue, Charolais, Friesian, Hereford, Holstein, Limousin, and Simmental. A multivariate animal model was used to estimate genetic parameters within the Holstein sire breed group. Univariate analyses were used to estimate variance components for the remaining 7 sire breed groups. Multivariate sire models were used to formally test differences in genetic variances in sire breed groups. Field data on 64,443 animals, which were slaughtered in commercial abattoirs between the ages of 300 and 875 d, were analyzed in 8 analyses. Carcass fat class and carcass conformation class were measured using the European Union beef carcass classification system (EUROP) scale. For all 3 traits, the sire breed group with the greatest genetic variance had a value of more than 8 times the sire breed group with least genetic variance. Heritabilities ranged from zero to moderate for carcass fatness class (0.00 to 0.40), from low to moderate for carcass conformation class (0.04 to 0.36), and from low to high for carcass weight (0.06 to 0.65). Carcass weight was the most heritable (0.26) of the 3 traits. Carcass conformation class and carcass fatness class were equally heritable (0.17). Genetic and phenotypic correlations were all positive in the Holstein sire breed group. The genetic correlations varied from 0.11 for the relationship between carcass weight and carcass fatness class to 0.44 for the relationship between carcass conformation class and carcass fatness class. Carcass weight and classification data collected in Irish abattoirs are useful for the purposes of genetic evaluation for beef traits of Irish cattle. There were significantly different variance components across the sire breed groups.  相似文献   

15.
Commercial slaughter steers (n = 329) and heifers (n = 335) were selected to vary in frame size, muscle score, and carcass fat thickness to study the effectiveness of live evaluation and ultrasound as predictors of carcass composition. Three trained personnel evaluated cattle for frame size, muscle score, fat thickness, longissimus muscle area, and USDA quality and yield grade. Live and carcass real-time ultrasound measures for 12th-rib fat thickness and longissimus muscle area were taken on a subset of the cattle. At the time of slaughter, carcass ultrasound measures were taken at "chain speed." After USDA grade data were collected, one side of each carcass was fabricated into boneless primals/subprimals and trimmed to .64 cm of external fat. Simple correlation coefficients showed a moderately high positive relationship between 12th rib fat thickness and fat thickness measures obtained from live estimates (r = .70), live ultrasound (r = .81), and carcass ultrasound (r = .73). The association between estimates of longissimus muscle area and carcass longissimus muscle area were significant (P < .001) and were higher for live evaluation (r = .71) than for the ultrasonic measures (live ultrasound, r = .61; carcass ultrasound, r = .55). Three-variable regression equations, developed from the live ultrasound measures, explained 57% of the variation in percentage yield of boneless subprimals, followed by live estimates (R2 = .49) and carcass ultrasound (R2 = .31). Four-variable equations using frame size, muscle score, and selected fat thickness and weight measures explained from 43% to 66% of the variation for the percentage yield of boneless subprimals trimmed to .64 cm. Live ultrasound and(or) live estimates are viable options for assessing carcass composition before slaughter.  相似文献   

16.
Genetic parameters for carcass traits of 1774 field progeny (1281 steers and 493 heifers), and their genetic relationships with feed efficiency traits of their sire population (740 bulls) were estimated with REML. Feed efficiency traits included feed conversion ratio (FCR) and residual feed intake (RFI). RFI was calculated by the residual of phenotypic (RFIphe) and genetic (RFIgen) regression from the multivariate analysis of feed intake on metabolic weight and daily gain. Progeny traits were carcass weight (CWT), rib eye area (REA), rib thickness (RBT), subcutaneous fat, yield estimate (YEM), marbling score (MSR), meat quality grade, meat color, fat color, meat firmness and meat texture. The estimated heritability for CWT (0.70) was high and heritabilities for all the other traits were moderate (ranged from 0.32 to 0.47), except for meat and fat color and meat texture which were low (ranged from 0.02 to 0.25). The high genetic correlation (0.62) between YEM and MSR suggests that simultaneous improvement of high carcass yield and beef marbling is possible. Estimated genetic correlations of RFI (RFIphe and RFIgen) of sires with CWT (− 0.60 and − 0.53) and MSR (− 0.62 and − 0.50) of their progeny were favorably negative indicating that the selection against RFI of sires may have contributed to produce heavier carcass and increase in beef marbling. The correlated responses in CWT, REA and RBT of progeny were higher to selection against RFI than those to selection against FCR of sires. This study provides evidence that selection against RFI is preferred over selection against FCR in sire population for getting better correlated responses in carcass traits of their progeny.  相似文献   

17.
Data from 534 steers representing six sire breed groups were used to develop live animal ultrasound prediction equations for weight and percentage of retail product. Steers were ultrasonically measured for 12th-rib fat thickness (UFAT), rump fat thickness (URPFAT), longissimus muscle area (ULMA), and body wall thickness (UBDWALL) within 5 d before slaughter. Carcass measurements included in USDA yield grade (YG) and quality grade calculations were obtained. Carcasses were fabricated into boneless, totally trimmed retail products. Regression equations to predict weight and percentage of retail product were developed using either live animal or carcass traits as independent variables. Most of the variation in weight of retail product was accounted for by live weight (FWT) and carcass weight with R2 values of 0.66 and 0.69, respectively. Fat measurements accounted for the largest portion of the variation in percentage of retail product when used as single predictors (R2 = 0.54, 0.44, 0.23, and 0.54 for UFAT, URPFAT, UBDWALL, and carcass fat, respectively). Final models (P < 0.10) using live animal variables included FWT, UFAT, ULMA, and URPFAT for retail product weight (R2 = 0.84) and UFAT, URPFAT, ULMA, UBDWALL, and FWT for retail product percentage (R2 = 0.61). Comparatively, equations using YG variables resulted in R2 values of 0.86 and 0.65 for weight and percentage of retail product, respectively. Results indicate that live animal equations using ultrasound measurements are similar in accuracy to carcass measurements for predicting beef carcass composition, and alternative ultrasound measurements of rump fat and body wall thickness enhance the predictive capability of live animal-based equations for retail yield.  相似文献   

18.
Growth and carcass data on 7,154 cattle from a purebred project and 1,241 cattle from a crossbred project, comprising 916 first-crosses and 325 purebred Brahman controls, were analyzed to estimate genetic parameters, including the genetic correlations between purebred and crossbred performance (rpc). The data also allowed the estimation of sire breed means for various growth and carcass traits. Crossbred calves were produced using 9 Angus, 8 Hereford, 7 Shorthorn, 14 Belmont Red, and 8 Santa Gertrudis sires bred to Brahman dams. These same sires produced 1,568 progeny in a separate purebreeding project. Cattle in both projects were managed under two finishing regimens (pasture and feedlot) to representative market live weights of 400 (domestic), 520 (Korean), and 600 kg (Japanese). The traits studied included live weight at around 400 d of age (400W), hot carcass weight (CWT), retail beef yield percentage (RBY), intramuscular fat percentage (IMF), rump fat depth (P8), and preslaughter ultrasound scanned eye muscle area (SEMA). Estimated breeding values (EBV) of sires from their BREEDPLAN genetic evaluations were used to assess their value in predicting crossbred performance. Regressions of actual crossbred calf performance on sire EBV for each of the traits differed little from their expectation of 0.5. Angus sires produced crossbred carcasses with the highest P8 and lowest RBY but highest IMF. In contrast, crossbred progeny from Belmont Red sires had the lightest 400W and CWT, lowest P8, and highest RBY. Estimates of rpc were 0.48, 0.48, 0.83, 0.95, 1.00, and 0.78 for 400W, CWT, RBY, IMF, P8, and SEMA, respectively. Commercial breeders selecting sires for crossbreeding programs with Brahman females, based on EBV computed from purebred data, might encounter some reranking of sire's performance for weight-related traits, with little expected change in carcass traits.  相似文献   

19.
Data (n = 1,746) collected from 1985 through 1995 on Korean Native Cattle by the National Livestock Research Institute of Korea were used to estimate genetic parameters for marbling score, dressing percentage, and longissimus muscle area, with backfat thickness, slaughter age, or slaughter weight as covariates. Estimates were obtained with REML. Model 1 included animal genetic and residual random effects. Model 2 was extended to include an uncorrelated random effect of the dam. Model 3 was based on Model 1 but also included sire x region x year-season interaction effects. Model 4 combined Models 2 and 3. All models included fixed effects for region x year-season and age of dam x sex combinations. From single-trait analyses, estimates of heritability with covariates to adjust for backfat thickness, slaughter age, and slaughter weight from Model 4 were, respectively, .10, .08, and .01 for marbling score; .09, .12, and .16 for dressing percentage; and .18, .17, and .24 for longissimus muscle area. From three-trait analyses, estimates of genetic correlations between marbling score and dressing percentage, marbling score and longissimus muscle area, and dressing percentage and longissimus muscle area were, respectively, -.99, .20, and -.11 with backfat thickness as covariate; -.88, .47, and .01 with slaughter age as covariate; and -.03, .39, and .91 with slaughter weight as covariate. Results of this study suggest that choice of covariate (backfat thickness, slaughter age, or slaughter weight) for the model seems to be important for carcass traits for Korean Native Cattle. Including sire x region x year-season interaction effects in the model for marbling score and dressing percentage may be important because whether sire x region x year-season interaction effects were in the model affected estimates of other variance components for the three carcass traits. Whether the maternal effect was in the model had little effect on estimates of other parameters. With backfat thickness and slaughter age end points, selection for increasing marbling score would be expected to result in decreasing dressing percentage for Korean Native Cattle. With slaughter weight as a covariate for end point, increased longissimus muscle area would be associated with increased dressing percentage, and increased marbling score would be related to increased longissimus muscle area. The differences in estimates associated with choice of end point, however, need further study.  相似文献   

20.
This study was conducted to determine the live weights at which large-, medium-, and small-framed feeder steers and heifers attain a degree of finish associated with a carcass quality grade of low Choice and to examine the relationship of feeder cattle muscle thickness to carcass yield grade traits. Feeder steers (n = 401) and heifers (n = 463) representing three age classes (calf, yearling, long yearling) were selected randomly at a commercial feedlot to exhibit wide ranges in frame size and muscularity. Individual weights were recorded and a panel of five experienced evaluators scored each animal for frame size, muscle thickness, and flesh condition. The cattle were finished on a high-concentrate finishing diet and harvested at an estimated carcass fat thickness of 10 mm. Final weights and USDA carcass grade data were collected for all cattle. Frame size scores effectively predicted finished weight at a marbling end point of Small(00) for both heifers (r2 = 0.89, SE = 16 kg) and steers (r2 = 0.94, SE = 13 kg). For heifers, the Small/Medium and Medium/ Large frame score intersects corresponded to live weights of 460 kg and 520 kg, respectively. For steers, the Small/Medium and Medium/Large frame score lines corresponded to live weights of 504 kg and 577 kg, respectively. These weights were greater than weights specified in the 1979 USDA grade standards. Evaluations of feeder cattle muscling, based on 1979 USDA Standards, were associated (P < 0.05) with differences in longissimus muscle area but were not related (P = 0.08) to differences in numerical carcass yield grades. An alternative muscle thickness classification scheme, involving the use of four thickness classes, was effective for stratifying feeder cattle according to eventual differences (P = 0.004) in carcass yield grade. Our findings suggest that USDA feeder cattle grade standards developed in 1979 are no longer adequate for describing today's population of feeder cattle.  相似文献   

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