J. Anim Sci. 2007. 85:2807-2814. doi:10.2527/jas.2007-0179
© 2007 American Society of Animal Science
Assessing the association of single nucleotide polymorphisms at the thyroglobulin gene with carcass traits in beef cattle1,2
E. Casas3,
S. N. White4,
S. D. Shackelford,
T. L. Wheeler,
M. Koohmaraie,
G. L. Bennett and
T. P. L. Smith
USDA, ARS, US Meat Animal Research Center, Clay Center, NE 68933
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Abstract
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The objective of this study was to assess the association of SNP in the thyroglobulin gene, including a previously reported marker in current industry use, with marbling score in beef cattle. Three populations, designated GPE6, GPE7, and GPE8, were studied. The GPE6 population sampled breeds that could be used as alternative germplasm sources in beef cattle production, including Wagyu, Swedish Red and White, Friesian, and Norwegian Red. The GPE7 population sampled 7 popular beef cattle breeds used in temperate climates of the United States: Angus, Charolais, Gelbvieh, Hereford, Limousin, Red Angus, and Simmental. The GPE8 population sampled Bos indicus-influenced breeds used in subtropical regions of the country and subtropical and tropical regions of the world, including Beefmaster, Bonsmara, Brangus, and Romosinuano. Evaluation of 6 SNP in the thyroglobulin gene, including 5 newly described variations, showed no association (P > 0.10) with marbling score in these populations, except a tendency (P < 0.10) for an association with the previously described marker in GPE6. Closer examination of the GPE6 data revealed that the source of the tendency was an association (P < 0.02) with marbling in animals of Wagyu inheritance. Animals having Wagyu background and inheriting the TT genotype had a greater marbling score (599 ± 20) than those inheriting the CC (540 ± 10) or the CT (541 ± 11) genotype. No association was detected with any other carcass trait for this marker in the 3 populations. Furthermore, none of the 5 newly described markers in the gene displayed an association with marbling score. The data indicate that markers at the thyroglobulin gene may be a useful predictor of marbling performance for producers raising Wagyu-based cattle. Although associations with marbling score in the remaining populations were not large or significant, the TT genotype had the numerically greatest marbling score in each population.
Key Words: beef cattle • carcass trait • marbling • thyroglobulin
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INTRODUCTION
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An important factor in determining carcass value is the amount of marbling, with high-premium carcasses exhibiting abundant intramuscular fat and little inter-muscular and subcutaneous fat (USDA, 1997
). Carcasses with Grade A maturity and at least a Slightly Abundant marbling score are classified as Prime, whereas those with much less marbling fat that have a Slight marbling score are classified as Select (USDA, 1997). Marbling is one of the most important factors in determining the value of beef carcasses, yet genetic selection programs to modify marbling in beef cattle have been limited, largely because of the time and expense necessary for progeny testing potential sires (Barendse et al., 2004). Several breed associations publish ultrasound-based marbling EPD. Deoxyribonucleic acid tests with predictive merit for marbling propensity would provide a useful tool to facilitate genetic progress in increased marbling.
Marbling is a quantitative trait affected by multiple genes and can display marked variation among individuals and breeds. A candidate gene proposed to affect marbling produces thyroglobulin (gene symbol TG), the precursor to thyroid hormones with known endocrine roles in fat metabolism (Barendse, 1999). An SNP upstream from the promoter of TG (marker TG5) has a reported association with marbling and is the source of a commercially available DNA test (Barendse, 1999; Barendse et al., 2004). However, studies of its effect on marbling in beef cattle have produced conflicting results (Barendse et al., 2004; Casas et al., 2005; Rincker et al., 2006).
Thus, the objective of this study was to assess the association of the TG5 and additional SNP in TG with marbling score in several populations by sampling a wide variety of beef cattle breeds.
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MATERIALS AND METHODS
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All experimental procedures were reviewed and accepted by the ARS Animal Care and Use Committee and were in accordance with the Federation of Animal Science Society’s Guide to care and use of agricultural animals in agricultural research and teaching.
Populations
Three populations were studied, representing different cycles of the US Meat Animal Research Center Germplasm Evaluation Project (Wheeler et al., 2006). Hereford and Angus sires were included in all 3 cycles to provide a link for statistical comparison; however, no purebred Hereford or Angus matings were made to avoid confounding sire breed effects with heterosis effects. These 2 breeds were treated as 1 breed group (British breeds) for statistical analysis. Cycle 6 of this project (GPE6 population) sampled sire breeds that could be used as alternative germplasm sources in beef cattle production (Wheeler et al., 2004; Casas and Cundiff, 2006). In the first year of the cycle, semen from Norwegian Red, Swedish Red and White, Wagyu, or Friesian sires was used on Hereford, Angus, and MARC III (one-fourth Angus, one-fourth Hereford, one-fourth Red Poll, one-fourth Pinzgauer) cows to produce a mixed F1 population. Heifers in the F1 generation were mated in 4 separate breeding pastures for 2 consecutive years, to 54 Charolais sires via multisire natural service (without record of individual sire-progeny relationships). This produced 653 crossbred steers and heifers. Details of the population structure, animal management, and feeding regimen have been described previously (Casas and Cundiff, 2006).
The second population was cycle 7 of the Germplasm Evaluation Project (GPE7), evaluating popular sire breeds used in the temperate areas of the United States. Details of the population structure, animal management, and feeding regimen have been reported previously (Wheeler et al., 2005). The GPE7 population was produced by using semen from Red Angus, Simmental, Gelbvieh, Limousin, and Charolais (as well as Angus and Hereford sires), with approximately equal numbers of calves produced from each sire breed (149 total sires, ranging from 18 to 23 sires per breed) produced from a similar population of Hereford, Angus, and MARCIII cows as GPE6. The population included 554 F1 steers.
The third population of animals came from cycle 8 of the Germplasm Evaluation Project (GPE8), and sampled sires from tropically adapted Bos indicus-influenced breeds, which are used in subtropical regions of the country and subtropical and tropical regions of the world (Wheeler et al., 2006). The GPE8 population was produced by using semen from Beefmaster, Brangus, Bonsmara, and Romosinuano bulls (as well as Angus and Hereford sires) on Angus and MARCIII cows. A total of 127 purebred sires were sampled, producing the 578 crossbred steers (approximately equal numbers of calves per sire breed) that were used in this study (Wheeler et al., 2006). Management of these animals and collection of phenotypes were similar to GPE7 (Wheeler et al., 2006).
Traits Evaluated
Marbling score was evaluated on a cross-section of the LM at the 12th- to 13th-rib interface as follows: Practically Devoid = 200 to 299; Traces = 300 to 399; Slight = 400 to 499; Small = 500 to 599; Modest = 600 to 699; Moderate = 700 to 799; Slightly Abundant = 800 to 899; Moderately Abundant = 900 to 999; and Abundant = 1,000 to 1,099 (USDA, 1997; Wheeler et al., 2005). In addition to marbling score, traits recorded for the animals were live BW (kg), postweaning ADG (kg/d), dressing percentage, yield grade, fat thickness (cm), LM area (LMA, cm2), HCW (kg), estimated KPH (%), retail product yield (%), fat yield (%), and bone yield (%). Retail, fat, and bone yields were estimated by using prediction equations that included carcass yield grade traits (LMA, adjusted fat thickness, and estimated KPH) and marbling score (Shackelford et al., 1995).
Markers Used and Genotyping Procedure
The previously reported SNP TG5 is a C/T in a repetitive element upstream from the promoter of the TG gene, located at position 422 of accession no. X05380 (Barendse, 1999). This polymorphism was genotyped as described by Casas et al. (2005). Additional SNP were detected by amplification of portions of the gene and sequencing of the PCR products from a panel of 32 animals, including representatives from each of the sire breeds in the GPE7 and GPE8 populations. The SNP were detected and annotated as described by Stone et al. (2002). The data for the markers has been deposited in the dbSNP database at the National Center for Bio-technology Information (www.ncbi.nlm.nih.gov; last accessed 7 September 2007) with accession numbers given in Table 1. The SNP were genotyped by PCR of each locus, followed by primer extension and product detection via mass spectrometry by using a Sequenom Mass-ARRAY genotyping system, as recommended by the manufacturer (Sequenom, La Jolla, CA). The primer sequences used for amplification and detection are given in Table 1.
A saturated salt procedure (Miller et al., 1988) was used to obtain DNA from white blood cells. Blood samples were collected in 60-mL syringes with 4% EDTA. Blood samples were collected from the jugular vein via needle puncture. Blood was spun at 2,500 rpm (1,300 x g) for 25 min and buffy coats were aspirated, cleaned, and frozen until DNA was extracted. A genotype for each animal was collected on the MassARRAY system, and the automated calls were checked by visualization of the spectrographs to minimize errors. Limited availability of buffy coats and problems with the degradation of existing DNA samples hampered the collection of a complete data set of all animals for all markers. When necessary, genotype assays were performed a second time to increase the number of successful genotypes, but genotype assays were not attempted a third time.
Statistical Methods
Models were evaluated by using the MIXED procedure (SAS Inst. Inc., Cary, NC). The model for GPE6 included fixed effects of maternal grandsire breed, maternal granddam breed, interaction of maternal grandsire breed and maternal granddam breed, sex class, year of birth, slaughter group within year, and TG5 genotype. The random effect of maternal grandsire within maternal grandsire breed and a linear covariate based on age at weaning also were included in the model. Further analysis of this population was pursued by evaluating animals with Wagyu inheritance and animals without Wagyu inheritance. When evaluating the population with Wagyu inheritance, a similar model was used, but the effects of maternal grandsire and the interaction of maternal grandsire breed and maternal granddam breed were excluded. When evaluating animals without Wagyu inheritance, the original statistical model was used. The model used for GPE7 and GPE8 included sire breed, dam breed, the interaction between sire breed and dam breed, year of birth, slaughter group within year, and TG5 genotype as fixed effects (White et al., 2005). Weaning age was included as a linear covariate. Sire was included as a random effect nested within sire breed. Probability values shown are nominal and not corrected for multiple testing.
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RESULTS
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The first goal was to determine the predictive merit of the previously reported TG5 marker, a C/T SNP upstream of the promoter now in commercial use, in the 3 crossbred populations. Genotyping of the GPE6, GPE7, and GPE8 animals indicated that T was the less frequent allele, present at 25, 24, and 21% frequency, respectively (Table 2). The frequency of the TT genotype was 7.7, 5.6, and 5.2% in GPE6, GPE7, and GPE8, respectively, providing sufficient numbers to estimate the effect of genotype for all 3 genotypic classes in each population. The models used for estimation of putative effects varied slightly among the populations because of their different structures; specifically, the GPE6 animals were of both sexes and had uncertain sires because of the natural service multisire pasture matings, whereas the GPE7 and GPE8 animals had known parentage, but were all steers. Classification of animals in the 3 populations by SNP genotype did not reveal any statistically significant association with marbling score (Table 3); however, in GPE6 there was a tendency (P < 0.10) for an association between marbling score and TG5.
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Table 2. Number of individuals inheriting the CC, CT, and TT genotypes at the TG5 marker in the GPE6,1 GPE7, and GPE8 populations
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Table 3. Level of significance, least squares means, and SE for the effect of the TG5 marker on various traits1 of the GPE6, GPE7, and GPE8 populations
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The original study reporting the TG5 marker (Barendse, 1999) was performed in a crossbred population by using the greatly marbled Wagyu breed, which suggested further examination of the marker in the GPE6 population that also incorporated Wagyu germplasm. As a consequence of the population structure in GPE6, the Wagyu alleles were transmitted to the phenotyped generation from the maternal grandsire. Table 4 shows a breakdown of GPE6 genotypes by maternal grandsire breed. All breeds had T as the allele with the lowest frequency (20 to 31% frequency). The Wagyu subpopulation had the greatest T allele frequency of any of the alternative maternal grandsire breeds (31%). The number of animals in the Wagyu subpopulation having the TT genotype was low (n = 17), potentially limiting the power to detect an association if the mode of inheritance is recessive. Despite this limitation, a significant (P < 0.02) association of the TG5 genotypes was detected with an apparently recessive mode of action, with the TT genotype having greater marbling than the CT or CC genotype class (Table 5). The remainder of the GPE6 animals, when analyzed separately from Wagyu as a group, showed no sign of a tendency toward association (Table 5).
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Table 4. Number of individuals inheriting the CC, CT, and TT genotypes, and allelic frequencies, at the TG5 marker by sire breed of the dam in the GPE61 population
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Table 5. Number of individuals, level of significance, least squares means, and SE for the effect of TG5 marker on marbling score1 in offspring derived from Wagyu maternal grandsires and non-Wagyu maternal grandsires in the GPE62 population
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Because the TG5 marker is in current application, it was of interest to determine whether it had detectable effects on other production-related traits despite a lack of detectable effect on marbling. However, no association was detected for any of the other 11 traits analyzed in these populations, indicating that selection would be neither beneficial nor detrimental to these phenotypes (Table 3
).
The data suggest the possibility that variation in TG might influence marbling, but that the reported TG5 marker is not in linkage disequilibrium with other functional loci, except in the Wagyu breed. Therefore, we developed additional markers in the gene to determine whether a marker in disequilibrium with a common variant affecting marbling in the most common US beef cattle breeds could be identified. Bovine TG is a relatively large gene including 48 exons spanning more than 200 kilobases of the genome. Fifteen genomic fragments of approximately 1 kilobase each, spread from intron 5 through exon 45, were sequenced in a discovery panel of 32 bovine genomic DNA samples (White et al., 2005) representing the sire breeds from GPE7 and GPE8 (data not shown). Five SNP were chosen for investigation based on the allele with the lowest frequency in the panel. Table 6 reports the genomic positions in the gene, as well as genotype frequencies of these markers in GPE7. The markers span a range of alleles, with the lowest frequencies from 3% (marker 668) to 46% (marker 957), and were not part of gene-wide haplotypes (i.e., the genotype at one marker was not predictive of the genotype at another; data not shown). Analysis of these 5 markers in GPE7 did not detect an association with marbling score (P > 0.1). Nominally significant associations (P < 0.05) of marker 551 with fat yield and bone yield, and of marker 668 with ADG, retail product yield, and fat yield were observed (Tables 7 and 8). However, these associations must be interpreted with caution.
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Table 6. Position in the gene and number of individuals per genotype in GPE71 for markers 993, 776, 551, 957, and 668
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Table 7. Level of significance, least squares means, and SE for the effect of marker 551 of the thyroglobulin gene on fat yield (FATYD) and bone yield (BONEYD) in the GPE71 population
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Table 8. Level of significance, least squares means, and SE for the effect of marker 668 of the thyroglobulin gene on postweaning ADG, retail product yield (RPYD), and fat yield (FATYD) in the GPE71 population
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DISCUSSION
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The objective of this study was to determine whether variation in the thyroglobulin gene was associated with marbling score and other carcass traits in 3 cattle populations. Conflicting reports have been published about the association of the TG5 SNP with marbling score in beef cattle (Thaller et al., 2003; Barendse et al., 2004; Casas et al., 2005; Rincker et al., 2006). This could be a result of the variable populations and production systems used in the analyses. Barendse et al. (2004) used purebred Angus and Shorthorn cattle of undetermined parentage fed for less than 250 d in Australia, and observed an association of the TG5 marker with marbling; Casas et al. (2005) examined Brahman cattle raised in Florida and fed approximately 140 d and failed to detect an association; Rincker et al. (2006) used Sim-mental cattle fed for approximately 250 d in Montana and failed to detect an association; Thaller et al. (2003) found an association between the TG5 marker and marbling score in a small German Holstein population but failed to find such an association in a Charolais population.
It is possible that the TG5 marker is in linkage disequilibrium with other functional loci in some genetic backgrounds but not others, or that the effect of the allele is dependent on the production system. The likelihood of the former is related to the average distance of linkage disequilibrium in this area of the bovine genome, the distance between the marker and functional variation responsible for the observed effect, and the natural history of cattle carrying the functional variant. The likelihood of environmental differences is even more difficult to determine, but could be critical for determining circumstances in which the marker can be successfully applied.
The populations used for our study represent a test for the association of marker genotype with phenotype (Page et al., 2004). The animals included a wide variety of breeds, individuals, and sire lines. Analyses of the 3 populations did not detect a significant association of the TG5 genotypes with marbling score. However, it is important to note that, whereas differences were not significant in any population, the TT genotype class had the greatest marbling score in all 3 populations (Table 3). The probability of this occurring at random, if the genotype has no effect on marbling, is less than 0.04 (0.33 x 0.33 x 0.33), suggesting that in these cattle populations the genotypic effect was obscured by some unaccounted for effect. Two of these populations (GPE7 and GPE8) have been used to identify significant effects of markers associated with meat tenderness (Page et al., 2004; White et al., 2005) and growth (White et al., 2007), demonstrating that they can be successfully used for this purpose. To increase the power of the study, it would be necessary to increase the frequency of the T allele in the populations to establish statistical differences, if they exist in outbred cattle populations, because no population with greater minor allele frequency and marbling phenotypes is currently available.
The current study detected an association of the TG5 marker with marbling in one subpopulation: the segment of GPE6 with Wagyu inheritance. In this subpopulation, animals with the TT genotype had significantly greater marbling scores than those with the other 2 genotypes. The fact that the effect was detected in a pedigree-defined subsample supports the hypothesis that the failure to observe an association was not due to environmental effects. One obvious source of this complication could be that the marker has a different phase with respect to causative variation in different genetic backgrounds. This phenomenon has previously been observed in studies of markers in the bovine µ-calpain (CAPN1) gene, in which the allele encoding Ile at AA 530 was found to be associated with decreased tenderness in the GPE7 population, but was found to increase tenderness in certain commercial populations used for validation studies (Page et al., 2004; R. Quaas, personal communication). It is likely that the TG5 marker will produce unreliable results in US beef cattle herds if used in a selection program to increase marbling.
Two hypotheses for the conflicting results with the TG5 marker are that it is relatively distant (in genetic units) from the causative variation, such that recombination has changed the phase of the marker allele in some cattle genomes, or that the T allele of the marker is associated with a mixture of multiple variations with differing effects on marbling, whose composition may differ among populations. The latter is more likely, because the mean for all populations was consistently greater for the TT genotype. Previous studies of CAPN1 locus markers and meat tenderness revealed a series of markers having associations in various phases in different populations, as mentioned above. By testing a number of markers in multiple populations, it was possible to develop marker systems with consistent predictive merit for this trait (White et al., 2005; Casas et al., 2006). These results suggested the possibility that, if functional variation in the TG gene commonly affects marbling in the GPE populations, different markers might produce more reliable results. To address these issues, additional SNP in the gene were identified and tested in an attempt to ascertain their utility in selection for increased marbling. However, none of the SNP developed displayed an association with marbling score in GPE7. These new markers were not evaluated in the other populations, because the goal was to identify markers with robust predictive merit for use in US beef cattle selection and management. A likely explanation for the data is that the causative variation being detected in populations showing an association lies relatively distant from the marker and is not an allele of the TG gene itself.
Quantitative trait loci for subcutaneous fat thickness and marbling score have been detected on chromosome 14, containing the TG gene, in a population of F2 cattle obtained from Wagyu and Limousin (Michal et al., 2006). However, the marbling score QTL was positioned telomeric from the TG gene, and the study reported an association of an SNP in the bovine fatty acid binding protein 4 (FABP4) gene with both marbling score and subcutaneous fat. The FABP4 gene is also positioned under QTL for fat thickness, as identified by Casas et al. (2000), Casas et al. (2003), and Moore et al. (2003), suggesting that it may be a reasonable candidate gene for harboring the putative causative variation for the marbling effect of TG5 in some populations. Two studies using Wagyu purebred families identified QTL for BW, carcass weight, and growth rate on chromosome 14, but did not detect an effect of the TG5 polymorphism or QTL for marbling (Mizoshita et al., 2004; Mizoguchi et al., 2006). This result suggests that the functional variation may be fixed in Wagyu, and previous studies with Wagyu crosses have detected the difference between this fixed allele in Wagyu and alleles present in other beef cattle breeds.
Additional markers developed in the thyroglobulin gene have shown an inconsistent association with carcass traits. Barendse et al. (2004) indicated that further discovery of SNP in the thyroglobulin gene should allow identification of the causal mutation. Markers developed at the gene in the current study indicate that the causal mutation is yet to be identified. Additional markers developed in the gene were not associated with marbling score in the GPE7 population; therefore, results of their association with other traits should be interpreted with extreme caution.
Further research will be needed to clarify the role of markers at the thyroglobulin gene in marbling or to develop alternative marker systems to track what appears to be likely variation in beef cattle on chromosome 14. Although associations of the TG5 marker have been observed (Barendse, 1999; Thaller et al., 2003; Barendse et al., 2004), there are also studies in which no association has been detected. The TG5 marker in the thyroglobulin gene promoter region does not appear to be a consistent, effective predictor of marbling score performance in common production environments in the United States.
The commercially available SNP reported in the thyroglobulin gene was associated with marbling score in cattle with Wagyu inheritance. The marker may explain a portion of the variation observed for marbling score in beef cattle. Further studies are needed to ascertain the effect of this marker on marbling score. Five additional markers developed in this gene were not associated with marbling score and were inconsistently associated with variation in other carcass traits of beef cattle.
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Footnotes
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1 Mention of trade names, proprietary products, or specified equipment does not constitute a guarantee or warranty by the USDA and does not imply approval to the exclusion of other products that may be suitable. 
2 The authors thank P. Beska, L. Flathman, R. Godtel, S. Nejez-chleb, S. Simcox, K. Simmerman, P. Tammen, and K. Tennill for technical assistance, the US Meat Animal Research Center staff for outstanding husbandry and animal care, and J. Watts for secretarial support.
4 Present address: USDA, ARS, Animal Disease Research Unit, Pullman, WA 99164-6630.
3 Corresponding author: Eduardo.Casas{at}ars.usda.gov
Received for publication March 21, 2007.
Accepted for publication July 26, 2007.
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LITERATURE CITED
|
|---|
Barendse, W. 1999. Assessing lipid metabolism. Int. Pat. Appl. PCT/AU98/00882, Int. Pat. Publ. WO 99/23248.
Barendse, W., R. Bunch, M. Thomas, S. Armitage, S. Baud, and N. Donaldson. 2004. The TG5 thyroglobulin gene test for a marbling quantitative trait loci evaluated in feedlot cattle. Aust. J. Exp. Agric. 44:669–674.[CrossRef]
Casas, E., and L. V. Cundiff. 2006. Postweaning growth and carcass traits in crossbred cattle from Hereford, Angus, Norwegian Red, Swedish Red and White, Friesian, and Wagyu maternal grandsires. J. Anim. Sci. 84:305–310.[Abstract/Free Full Text]
Casas, E., S. D. Shackelford, J. W. Keele, M. Koohmaraie, T. P. L. Smith, and R. T. Stone. 2003. Detection of quantitative trait loci for growth and carcass composition in cattle. J. Anim. Sci. 81:2976–2983.[Abstract/Free Full Text]
Casas, E., S. D. Shackelford, J. W. Keele, R. T. Stone, S. M. Kappes, and M. Koohmaraie. 2000. Quantitative trait loci affecting growth and carcass composition of cattle segregating alternate forms of myostatin. J. Anim. Sci. 78:560–569.[Abstract/Free Full Text]
Casas, E., S. N. White, D. G. Riley, T. P. L. Smith, R. A. Brenneman, T. A. Olson, D. D. Johnson, S. W. Coleman, G. L. Bennett, and C. C. Chase Jr. 2005. Assessment of single nucleotide polymorphisms in genes residing on chromosomes 14 and 29 for association with carcass composition traits in Bos indicus cattle. J. Anim. Sci. 83:13–19.[Abstract/Free Full Text]
Casas, E., S. N. White, T. L. Wheeler, S. D. Shackelford, M. Koohmaraie, D. G. Riley, C. C. Chase Jr., D. D. Johnson, J. W. Keele, and T. P. L. Smith. 2006. Effects of calpastatin and micro-calpain markers in beef cattle on tenderness traits. J. Anim. Sci. 84:520–525.[Abstract/Free Full Text]
Michal, J. J., Z. W. Zhang, C. T. Gaskins, and Z. Jiang. 2006. The bovine fatty acid binding protein 4 gene is significantly associated with marbling and subcutaneous fat depth in Wagyu x Limousin F2 crosses. Anim. Genet. 37:400–402.[CrossRef][Medline]
Miller, S. A., D. D. Dykes, and H. F. Polesky. 1988. A simple salting out procedure for extracting DNA from human nucleated cells. Nucleic Acids Res. 16:1215.[Free Full Text]
Mizoguchi, Y., T. Watanabe, K. Fujinaka, E. Iwamoto, and Y. Sugimoto. 2006. Mapping of quantitative trait loci for carcass traits in a Japanese Black (Wagyu) cattle population. Anim. Genet. 37:51–54.[CrossRef][Medline]
Mizoshita, K., T. Watanabe, H. Hayashi, C. Kubota, H. Yamakuchi, J. Todoroki, and Y. Sugimoto. 2004. Quantitative trait loci analysis for growth and carcass traits in a half-sib family of purebred Japanese Black (Wagyu) cattle. J. Anim. Sci. 82:3415–3420.[Abstract/Free Full Text]
Moore, S. S., C. Li, J. Basarab, W. M. Snelling, J. Kneeland, B. Murdoch, C. Hansen, and B. Benkel. 2003. Fine mapping of quantitative trait loci and assessment of positional candidate genes for backfat on bovine chromosome 14. J. Anim. Sci. 81:1919–1925.[Abstract/Free Full Text]
Page, B. T., E. Casas, R. L. Quaas, R. M. Thallman, T. L. Wheeler, S. D. Shackelford, M. Koohmaraie, S. N. White, G. L. Bennett, J. W. Keele, M. E. Dikeman, and T. P. L. Smith. 2004. Association of markers in the bovine CAPN1 gene with meat tenderness in large crossbred populations that sample influential industry sires. J. Anim. Sci. 82:3474–3481.[Abstract/Free Full Text]
Rincker, C. B., N. A. Pyatt, L. L. Berger, and D. B. Faulkner. 2006. Relationship among GeneSTAR marbling marker, intramuscular fat deposition, and expected progeny differences in early weaned Simmental steers. J. Anim. Sci. 84:686–693.[Abstract/Free Full Text]
Shackelford, S. D., L. V. Cundiff, K. E. Gregory, and M. Koohmaraie. 1995. Predicting beef carcass cutability. J. Anim. Sci. 73:406–413.[Abstract]
Stone, R. T., W. M. Grosse, E. Casas, T. P. L. Smith, J. W. Keele, and G. L. Bennett. 2002. Use of bovine EST data and human genomic sequences to map 100 gene-specific bovine markers. Mamm. Genome 13:211–215.[CrossRef][Medline]
Thaller, G., C. Kuhn, A. Winter, G. Ewald, O. Bellman, J. Wegner, H. Zuhlke, and R. Fries. 2003. DGAT1, a new positional and functional candidate gene for intramuscular fat deposition in cattle. Anim. Genet. 34:354–357.[CrossRef][Medline]
USDA. 1997. Official United States Standards for Grades of Carcass Beef. Agric. Marketing Service, USDA, Washington, DC.
Wheeler, T. L., L. V. Cundiff, S. D. Shackelford, and M. Koohmaraie. 2004. Characterization of biological types of cattle (Cycle VI): Carcass, yield, and longissimus muscle palatability traits. J. Anim. Sci. 82:1177–1189.[Abstract/Free Full Text]
Wheeler, T. L., L. V. Cundiff, S. D. Shackelford, and M. Koohmaraie. 2005. Characterization of biological types of cattle (Cycle VII): Carcass, yield, and longissimus palatability traits. J. Anim. Sci. 83:196–207.[Abstract/Free Full Text]
Wheeler, T. L., L. V. Cundiff, L. D. Van Vleck, G. D. Snowder, R. M. Thallman, S. D. Shackelford, and M. Koohmaraie. 2006. Preliminary results from Cycle VIII of the Cattle Germplasm Evaluation Program at the U. S. Meat Animal Research Center. Germplasm Evaluation Program Progress Report No. 23. Agric. Res. Serv., USDA, Clay Center, NE.
White, S. N., E. Casas, M. F. Allan, J. W. Keele, W. N. Snelling, T. L. Wheeler, S. D. Shackelford, M. Koohmaraie, and T. P. L. Smith. 2007. Beef cattle evaluation of six DNA markers developed for dairy traits reveals an osteopontin polymorphism is associated with post-weaning growth. J. Anim. Sci.
White, S. N., E. Casas, T. L. Wheeler, S. D. Shackelford, M. Koohmaraie, D. G. Riley, C. C. Chase Jr., D. D. Johnson, J. W. Keele, and T. P. L. Smith. 2005. A new single nucleotide polymorphism in CAPN1 extends the current tenderness marker test to include cattle of Bos indicus, Bos taurus, and crossbred descent. J. Anim. Sci. 83:2001–2008.[Abstract/Free Full Text]
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Abstract
INTRODUCTION
