Effect of myostatin F94L on carcass yield in cattle

Relationship between Some Myostatin Variants and Meat Production Related Calving, Weaning and Muscularity Traits in Charolais Cattle

The slaughter value of live cattle can be assessed during visual conformation scoring, as well as by examining different molecular genetic information, e.g., the myostatin gene, which can be responsible for muscle development. In this study, the F94L, Q204X, nt267, nt324 and nt414 alleles of the myostatin gene (MSTN) were examined in relation to birth weight (BIW), calving ease (CAE), 205-day weaning weight (CWW), muscle score of shoulder (MSS), muscle score of back (MSB), muscle score of thigh (MST), roundness score of thigh (RST), loin thickness score (LTS), and overall muscle development percentage (OMP) of Charolais weaned calves in Hungary. Multi-trait analysis of variance (GLM) and weighted linear regression analysis were used to process the data. Calves carrying the Q204X allele in the heterozygous form achieved approximately 0.14 points higher MSB, MST and LTS, and 1.2% higher OMP, and gained 8.56 kg more CWW than their counterparts not carrying the allele (p < 0.05). As for the F94L allele, there was a difference of 4.08 kg in CWW of the heterozygous animals, but this difference could not be proved statistically. The other alleles had no significant effect on the evaluated traits.

Polymorphism of Genes and Their Impact on Beef Quality

The single-nucleotide polymorphism (SNP) form of genes is a valuable source of information regarding their suitability for use as specific markers of desirable traits in beef cattle breeding. For several decades, breeding work focused on improving production efficiency through optimizing the feed conversion ratio and improving daily gains and meat quality. Many research teams previously undertook research work on single-nucleotide polymorphism in myostatin (MSTN), thyroglobulin (TG), calpain (CAPN), and calpastatin (CAST) proteins. The literature review focuses on the most frequently addressed issues concerning these genes in beef cattle production and points to a number of relevant studies on the genes' polymorphic forms. The four genes presented are worth considering during breeding work as a set of genes that can positively influence productivity and production quality.

Effects of the F94L myostatin gene mutation in beef × dairy crossed cattle on muscle fiber type, live performance, carcass characteristics, and boxed beef and retail cut yields

Producer live performance data and carcasses from steers (n = 116) resulting from the mating of four Limousin/Angus sires heterozygous for the F94L myostatin mutation to Jersey/Holstein dams were utilized to evaluate the effects of one copy of the F94L allele on live performance, carcass traits and USDA grades, and boxed beef and retail yields. Slaughter data were collected at time of harvest and carcass data were collected 48 hours postmortem. One side from each of the 58 carcasses was fabricated into boxed beef and retail cuts by experienced lab personnel 5-8 d postmortem. One copy of the F94L allele did not affect gestation length, birth weight, percentage of unassisted births, feedlot average daily gain, live weight at harvest, hot carcass weight, or dressing percentage (P > 0.05). Muscle fiber analysis indicated that the increase in muscularity by the F94L allele in the semitendinosus and longissimus was likely due to hyperplasia as there was a 19% increase in the quantity of myosin heavy chain type IIA and IIX fibers in the semitendinosus (P < 0.05) with no effect on muscle fiber size (P > 0.05). Carcasses from steers with one F94L allele had larger ribeye areas (99.2 vs. 92.3 sq.cm.), greater ribeye width:length ratios (0.498 vs. 0.479), lower USDA yield grades (2.21 vs. 2.66), and lower marbling scores (438 vs. 480) (P < 0.05). Additionally, for boxed beef yields, one F94L allele, vs. zero F94L alleles, increased (P < 0.05) 85/15 trimmings (+0.59%), top round (+0.28%), strip loin (+0.12%), eye round (+0.11%), tenderloin (+0.07%), boneless foreshank (+0.07%), cap/wedge (+0.06%), and tri-tip (+0.04%). Overall, carcasses from steers with one F94L allele had a greater boxed beef yield (+1.06%), boxed beef plus 85/15 trimmings yield (+1.65%), and total retail cuts plus ground beef 85/15 yield (+1.78%) than carcasses from steers with zero F94L alleles (P < 0.05). One copy of the F94L allele utilized in beef-on-dairy breeding system had no significant impact on live performance traits but resulted in lower marbling scores and increased muscularity as evidenced through larger, more beef-shaped ribeyes, lower USDA yield grades, and greater carcass cutout yields (both boxed beef and retail yields).

Growth Traits and Sperm Proteomics Analyses of Myostatin Gene-Edited Chinese Yellow Cattle

Chinese Yellow Cattle, an ancient and domesticated breed for draft service, provide unique animal genetic resources with excellent genetic features, including crude feed tolerance, good stress resistance, strong adaptability, and tender meat quality; however, their production performance and meat yield are significantly inferior. Herein, the myostatin gene (MSTN), a negative regulator of skeletal muscle development, was knocked out by CRISPR/Cas9 technology. Eight MSTN gene-edited bull calves (MT) were born, and six of them are well-developed. Compared with the control cattle (WT), the growth trait indexes of MT cattle were generally increased, and the hindquarters especially were significantly improved. The biochemical indexes and the semen characteristics demonstrated that MT bulls were healthy and fertile. Consistent with our conjecture, the wobble and beating of MT bull spermatozoa were significantly higher than that of WT. Nine sperm motility-related proteins and nineteen mitochondrial-related proteins were identified by up-regulation in MT bull spermatozoa using FLQ proteomic technique and act to govern sperm flagellum assembly, organization, and beating and provide sufficient energy for sperm motility. The current study confirmed that the MSTN gene-edited Chinese Yellow cattle have improved growth traits and normal fertility, which can be used for beef cattle production and breeding.

Genetic Variations and Haplotypic Diversity in the Myostatin Gene of Different Cattle Breeds in Russia

Simple Summary

This paper presents the results of the study of two polymorphisms of the myostatin gene associated with muscular hypertrophy in the Russian populations of Aberdeen Angus, Limousin, Simmental, and Belgian Blue cattle breeds. For their diagnostics, test systems based on modern molecular genetic methods were developed, and the population analysis showed a low frequency of the undesirable allele associated with the genetic defect of double-muscling, and a high frequency of the allele that presumably positively influences meat productivity traits.

Abstract

The myostatin gene (MSTN) in cattle has a number of polymorphisms associated with increased muscle mass. The aim of the current study was to determine the haplotype frequencies of F94L and nt821(del11) MSTN polymorphisms among cattle bred for meat in Russia, using DNA analysis. Using the earlier created test systems based on the AS-PCR and PCR-RFLP methods, six populations of Aberdeen Angus (n = 684), two populations of Limousin (n = 54), one population of Simmental (n = 55), and one population of Belgian Blue (n = 137) belonging to Russian farms were genotyped on nt821(del11) and F94LMSTN polymorphisms. The animal carriers of the mutant allele of nt821(del11)MSTN associated with the double-muscling genetic defect were found in one Aberdeen Angus population at a frequency of 2.18%, but were not found in the Limousin and Simmental populations. However, 100% of the Belgian Blue population were heterozygous carriers of nt821(del11)MSTN. The frequencies of the A allele F94LMSTN desirable for productivity traits in the Limousin populations were the highest and accounted for 0.97 and 1 in populations one and two, while in the Aberdeen Angus, Simmental, and Belgian Blue populations, these figures were considerably lower at 0.04–0.08, depending on the population. The obtained data show the high genetic potential of Russian beef cattle, and facilitate an improvement in meat productivity by preserving the health of animals.

The Blonde d'Aquitaine T3811>G3811 mutation in the myostatin gene: association with growth, carcass, and muscle phenotypes in veal calves

The mutation T3811 → G3811 (TG3811) discovered in the myostatin gene of the Blonde d'Aquitaine breed is suspected of contributing to the outstanding muscularity of this breed. An experiment was designed to estimate the effect of this mutation in an F2 and back-cross Blonde d'Aquitaine × Holstein population. By genotyping all known mutations in the myostatin gene, it was ensured that the TG3811 mutation was indeed the only known mutation segregating in this population. Fifty-six calves (43 F2, 13 back-cross) were intensively fattened and slaughtered at 24.0 ± 1.4 wk of age. The effects of the mutation were estimated by comparing the calves with the [T/T] (n = 18), [T/G] (n = 30), and [G/G] (n = 8) genotypes. Highly significant substitution effects (P < 0.001), above + 1.2 phenotypic SD, were shown on carcass yield and muscularity scores. Birth weight (P < 0.001) was positively affected by the mutation (+0.8 SD) but not growth rate (P = 0.97), while carcass length (P = 0.03), and fatness (P ≤ 0.03) were negatively affected (-0.5 to -0.7 SD). The characteristics of the Triceps brachii muscle were affected by the mutation (P < 0.001), with lower ICDH activity (oxidative) and a higher proportion of myosin type 2X muscle fibers (fast twitch). The effects of the TG3811 mutation were similar to those of other known myostatin mutations, although the Blonde d'Aquitaine animals, which are predominantly [G/G] homozygous, do not exhibit extreme double muscling.

DNA analysis of the Russian populations of Aberdeen Angus, Hereford and Belgian Blue cattle

The use of specialized meat breeds in cattle breeding programs is considered very promising for improving herds' productivity. However, in animal genotype, along with genes that positively affect the productivity signs, there are genes whose mutations, known as genetic defects, negatively affect the health of animals. The aim of the study was the screening of the Russian populations of Aberdeen Angus, Hereford and Belgian Blue cattle on gene mutations associated with the genetic defects of arthrogryposis multiplex (AM), osteopetrosis (OS), developmental duplication (DD), double muscling (M1), hypotrichosis (HY) and maple syrup urine disease (MSUD) as well as the F94L polymorphism of myostatin gene (MSTN) linked with the gene responsible for less fat content in the carcass by means of DNA analysis. In the article, test systems based on the polymerase chain reaction method are presented. The analysis of the Aberdeen Angus (n=4480) population has revealed 0.19 ± 0.09 % animal M1 carriers, 0.53 ± 0.03 % OS carriers, 1.92 ± 0.09 % AM carriers and 9.00 ± 0.20 % DD carriers. The genotyping of Hereford cattle of Russian populations (n=525) has not revealed any individual carriers of MSUD or HY genetic defects. All of the Belgian Blue population (n=92) animals were heterozygous M1 carriers. The study of the F94LMSTN polymorphism has demonstrated extremely high frequencies of the desirable A allele (0.93 and 0.90) in two Aberdeen Angus populations with an average mean of 0.63 ± 0.08, which was 32 % higher compared to the Belgian Blue population. The results suggest the high genetic potential of the Aberdeen Angus and Belgian Blue cattle, but the existence in the genotypes of the mutant alleles associated with hereditary diseases indicates the risk of uncontrolled use of these breeds.

Associations of CAST, CAPN1 and MSTN Genes Polymorphism with Slaughter Value and Beef Quality – A Review

The slaughter value of cattle and beef quality are influenced by many factors, which can generally be divided into antemortem (breed, sex, age, housing system, diet, pre-slaughter handling) and postmortem (post-slaughter processing, chilling temperature, packaging). Studies of many authors have shown that meat quality traits can be also influenced by the individual genetic background of an animal. Numerous studies have been conducted worldwide to determine the functions of various genes as well as polymorphisms with potential effects on fattening and slaughter value of cattle and on beef quality. This study reviews the most important research done on the associations of polymorphisms in the calpain, calpastatin and myostatin genes with carcass traits and beef quality. Knowledge about the genes and chromosome regions associated with desired meat quality characteristics may prove very helpful when selecting pairs for mating and estimating the breeding value of offspring, mainly because it is difficult to improve meat quality traits based on conventional selection methods due to their low heritability and polygenic regulation. Furthermore, meat quality evaluation is expensive and can only be carried out after slaughter.

Detection of selection signatures in Limousin cattle using whole-genome resequencing

Limousin, a renowned beef breed originating from central France, has been selectively bred over the last 100 years to improve economically important traits. We used whole-genome sequencing data from 10 unrelated Limousin bull calves to detect polymorphisms and identify regions under selection. A total of 13 943 766 variants were identified. Moreover, 311 852 bi-allelic SNPs and 92 229 indels located on autosomes were fixed for the alternative allele in all sequenced animals, including the previously reported missense deleterious F94L mutation in MSTN. We performed a whole-genome screen to discover genomic regions with excess homozygosity, using the pooled heterozygosity score and identified 171 different candidate selective sweeps. In total, 68 candidate genes were found in only 57 of these regions, indicating that a large fraction of the genome under selection might lie in non-coding regions and suggesting that a majority of adaptive mutations might be regulatory in nature. Many QTL were found within candidate selective sweep regions, including QTL associated with shear force or carcass weight. Among the putative selective sweeps, we located genes (MSTN, NCKAP5, RUNX2) that potentially contribute to important phenotypes in Limousin. Several candidate regions and genes under selection were also found in previous genome-wide selection scans performed in Limousin. In addition, we were able to pinpoint candidate causative regulatory polymorphisms in GRIK3 and RUNX2 that might have been under selection. Our results will contribute to improved understanding of the mechanisms and targets of artificial selection and will facilitate the interpretation of GWASs performed in Limousin.

Effects of polymorphism of myostatin and fatty acid-binding protein 4 genes on the chemical composition of meat in cull female Aceh cattle

Aim:

This study aimed to investigate the association of single nucleotide polymorphism of the myostatin (MSTN) and fatty acid-binding protein 4 (FABP4) genes on the total water, ash, fat, protein, and cholesterol contents of sirloin (gluteus medius muscle) and silverside (biceps femoris muscle) meats of cull female Aceh cattle.

Materials and Methods:

This analysis covered a total of 27 cull female Aceh cattle slaughtered at the Animal Slaughterhouse of Banda Aceh that was purposively selected based on hair color referred to the criteria described in the Decree of Ministry of Agriculture of the Republic of Indonesia. Genomic DNA was extracted from 25 mg of fresh meat using the spin column method before subjected to a polymerase chain reaction amplification using primer sets specific for 1346-bp and 275-bp fragments of MSTN and FABP4, respectively. A 4-h digestion reaction was done separately for the MSTN/HaeIII and FABP4/NlaIII loci genotyping. The total protein, ash, and fat of the meat were measured using the Indonesian National Standard (SNI) methods whereas its cholesterol content was determined using the AOAC method. The association between each polymorphism and the variation in meat chemical parameters was analyzed using the Pearson correlation test.

Results:

The results showed that the MSTN/HaeIII locus was polymorphic in Aceh cattle, but the FABP4/NlaIII locus was monomorphic. Meat chemical parameters were not influenced by different commercial cuts and MSTNgenotypes, showing that there was no association between different commercial cuts, cattle hair colors, and MSTN/HaeIII and FABP4/NlaIII markers with the meat chemical parameters in Aceh cattle.

Conclusion:

These results suggest that focusing on the novel effects of MSTN and FABP4 gene polymorphisms on meat production traits might not be useful for marker-assisted selection in Aceh cattle.

Whole-genome resequencing analysis of 20 Micro-pigs

BACKGROUND

Miniature pigs have been increasingly used as mammalian model animals for biomedical research because of their similarity to human beings in terms of their metabolic features and proportional organ sizes. However, despite their importance, there is a severe lack of genome-wide studies on miniature pigs.

OBJECTIVE

In this study, we performed whole-genome sequencing analysis of 20 Micro-pigs obtained from Medi Kinetics to elucidate their genomic characteristics.

RESULTS

Approximately 595 gigabase pairs (Gb) of sequence reads were generated to be mapped to the swine reference genome assembly (Sus scrofa 10.2); on average, the sequence reads covered 99.15% of the reference genome at an average of 9.6-fold coverage. We detected a total of 19,518,548 SNPs, of which 8.7% were found to be novel. With further annotation of all of the SNPs, we retrieved 144,507 nonsynonymous SNPs (nsSNPs); of these, 5968 were found in all 20 individuals used in this study. SIFT prediction for these SNPs identified that 812 nsSNPs in 402 genes were deleterious. Among these 402 genes, we identified some genes that could potentially affect traits of interest in Micro-pigs, such as RHEB and FRAS1. Furthermore, we performed runs of homozygosity analysis to locate potential selection signatures in the genome, detecting several loci that might be involved in phenotypic characteristics in Micro-pigs, such as MSTN, GDF5, and GDF11.

CONCLUSION

In this study, we identified numerous nsSNPs that could be used as candidate genetic markers with involvement in traits of interest. Furthermore, we detected putative selection footprints that might be associated with recent selection applied to miniature pigs.

Reaffirmation of known major genes and the identification of novel candidate genes associated with carcass-related metrics based on whole genome sequence within a large multi-breed cattle population

Background

The high narrow sense heritability of carcass traits suggests that the underlying additive genetic potential of an individual should be strongly correlated with both animal carcass quality and quantity, and therefore, by extension, carcass value. Therefore, the objective of the present study was to detect genomic regions associated with three carcass traits, namely carcass weight, conformation and fat cover, using imputed whole genome sequence in 28,470 dairy and beef sires from six breeds with a total of 2,199,926 phenotyped progeny.

Results

Major genes previously associated with carcass performance were identified, as well as several putative novel candidate genes that likely operate both within and across breeds. The role of MSTN in carcass performance was re-affirmed with the segregating Q204X mutation explaining 1.21, 1.11 and 5.95% of the genetic variance in carcass weight, fat and conformation, respectively in the Charolais population. In addition, a genomic region on BTA6 encompassing the NCAPG/LCORL locus, which is a known candidate locus associated with body size, was associated with carcass weight in Angus, Charolais and Limousin. Novel candidate genes identified included ZFAT in Angus, and SLC40A1 and the olfactory gene cluster on BTA15 in Charolais. Although the majority of associations were breed specific, associations that operated across breeds included SORCS1 on BTA26, MCTP2 on BTA21 and ARL15 on BTA20; these are of particular interest due to their potential informativeness in across-breed genomic evaluations. Genomic regions affecting all three carcass traits were identified in each of the breeds, although these were mainly concentrated on BTA2 and BTA6, surrounding MSTN and NCAPG/LCORL, respectively. This suggests that although major genes may be associated with all three carcass traits, the majority of genes containing significant variants (unadjusted p-value < 10^− 4) may be trait specific associations of small effect.

Conclusions

Although plausible novel candidate genes were identified, the proportion of variance explained by these candidates was minimal thus reaffirming that while carcass performance may be affected by major genes in the form of MSTN and NCAPG/LCORL, the majority of variance is attributed to the additive (and possibly multiplicative) effect of many polymorphisms of small effect.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-6071-9) contains supplementary material, which is available to authorized users.

Association between expression levels and growth trait-related SNPs located in promoters of the MC4R and MSTN genes in Spinibarbus hollandi

Melanocortin 4 receptor: (MC4R) and Myostatin (MSTN) are two important growth trait-related genes in animals. In this study, we showed that two SNPs, MC4R-719A>G and MSTN-519C>T, found in the promoters of the MC4R and MSTN genes, respectively, are both associated with growth traits in Spinibarbus hollandi. Furthermore, we observed that there were significant associations between the expression levels of the MC4R and MSTN genes and these two growth trait-related SNPs. The expression level of MC4R gene in brain was lower in GG genotype fish with extremely high growth performance than that in AA genotype fish with extremely low growth performance. Expression level of the MSTN gene in muscle was lower in TT genotype fish with extremely high growth performance than that in CC and CT genotype fish with lower growth performance. The results indicated that these SNPs located in the promoters of MC4R and MSTN are associated with growth-related traits through modification of gene expression levels. The MSTN and MC4R SNPs may have useful application in effective marker-assisted selection aimed to increase output in S. hollandi.

Genetic disorders in beef cattle: a review

The main purpose of present review is to describe and organize autosomal recessive disorders (arachnomelia, syndactylism, osteopetrosis, dwarfism, crooked tail syndrome, muscular hyperplasia, glycogen storage disease, protoporphyria), which occur among beef cattle, and methods that can be applied to detect these defects. Prevalence of adverse alleles in beef breeds happens due to human activity—selections of favorable features, e.g. developed muscle tissue. Unfortunately, carriers of autosomal recessive diseases are often characterized by these attributes. Fast and effective identification of individuals, that may carry faulty genes, can prevent economical losses.

Construction of a large collection of small genome variations in French dairy and beef breeds using whole-genome sequences

Background

In recent years, several bovine genome sequencing projects were carried out with the aim of developing genomic tools to improve dairy and beef production efficiency and sustainability.

Results

In this study, we describe the first French cattle genome variation dataset obtained by sequencing 274 whole genomes representing several major dairy and beef breeds. This dataset contains over 28 million single nucleotide polymorphisms (SNPs) and small insertions and deletions. Comparisons between sequencing results and SNP array genotypes revealed a very high genotype concordance rate, which indicates the good quality of our data.

Conclusions

To our knowledge, this is the first large-scale catalog of small genomic variations in French dairy and beef cattle. This resource will contribute to the study of gene functions and population structure and also help to improve traits through genotype-guided selection.

Electronic supplementary material

The online version of this article (doi:10.1186/s12711-016-0268-z) contains supplementary material, which is available to authorized users.

Gene-based single nucleotide polymorphism discovery in bovine muscle using next-generation transcriptomic sequencing

Background

Genetic information based on molecular markers has increasingly being used in cattle breeding improvement programmes, as a mean to improve conventionally phenotypic selection. Advances in molecular genetics have led to the identification of several genetic markers associated with genes affecting economic traits. Until recently, the identification of the causative genetic variants involved in the phenotypes of interest has remained a difficult task. The advent of novel sequencing technologies now offers a new opportunity for the identification of such variants. Despite sequencing costs plummeting, sequencing whole-genomes or large targeted regions is still too expensive for most laboratories. A transcriptomic-based sequencing approach offers a cheaper alternative to identify a large number of polymorphisms and possibly to discover causative variants. In the present study, we performed a gene-based single nucleotide polymorphism (SNP) discovery analysis in bovine Longissimus thoraci, using RNA-Seq. To our knowledge, this represents the first study done in bovine muscle.

Results

Messenger RNAs from Longissimus thoraci from three Limousin bull calves were subjected to high-throughput sequencing. Approximately 36–46 million paired-end reads were obtained per library. A total of 19,752 transcripts were identified and 34,376 different SNPs were detected. Fifty-five percent of the SNPs were found in coding regions and ~22% resulted in an amino acid change. Applying a very stringent SNP quality threshold, we detected 8,407 different high-confidence SNPs, 18% of which are non synonymous coding SNPs. To analyse the accuracy of RNA-Seq technology for SNP detection, 48 SNPs were selected for validation by genotyping. No discrepancies were observed when using the highest SNP probability threshold. To test the usefulness of the identified SNPs, the 48 selected SNPs were assessed by genotyping 93 bovine samples, representing mostly the nine major breeds used in France. Principal component analysis indicates a clear separation between the nine populations.

Conclusions

The RNA-Seq data and the collection of newly discovered coding SNPs improve the genomic resources available for cattle, especially for beef breeds. The large amount of variation present in genes expressed in Limousin Longissimus thoracis, especially the large number of non synonymous coding SNPs, may prove useful to study the mechanisms underlying the genetic variability of meat quality traits.

Molecular characterization of myostatin (MSTN) gene and association analysis with growth traits in the bighead carp (Aristichthys nobilis)

Myostatin (MSTN) is a member of the transforming growth factor-β superfamily and functions as a negative regulator of skeletal muscle development and growth. In this study, the bighead carp MSTN gene (AnMSTN for short) was cloned and characterized. The 3,769 bp genomic sequence of AnMSTN consisted of three exons and two introns, and the full length cDNA (2,141 bp) of the gene had an open reading frame encoding a polypeptide of 375 amino acids. The deduced amino acid sequence of AnMSTN showed 67.1-98.7 % homology with MSTNs of avian, mammalian and teleostean species. Sequence comparison and phylogenetic analysis confirmed the MSTNs were conserved throughout the vertebrates and AnMSTN belonged to MSNT-1 isoform. AnMSTN was expressed in various tissues with the highest expression in muscle. Two single nucleotide polymorphisms, g.1668T > C in intron 2 and g.2770C > A in 3' UTR, were identified in AnMSTN by sequencing PCR fragments, and genotyped by SSCP. Association analysis showed that g.2770C > A genotypes were significantly associated with total length, body length and body weight (P < 0.01). These results suggest that AnMSTN involves in the regulation of growth, and this polymorphism would be informative for further studies on selective breeding in bighead carp.

Quantitative trait loci for organ weights and adipose fat composition in Jersey and Limousin back-cross cattle finished on pasture or feedlot

A QTL study of live animal and carcass traits in beef cattle was carried out in New Zealand and Australia. Back-cross calves (385 heifers and 398 steers) were generated, with Jersey and Limousin backgrounds. This paper reports on weights of eight organs (heart, liver, lungs, kidneys, spleen, gastro-intestinal tract, fat, and rumen contents) and 12 fat composition traits (fatty acid (FA) percentages, saturated and monounsaturated FA subtotals, and fat melting point). The New Zealand cattle were reared and finished on pasture, whilst Australian cattle were reared on grass and finished on grain for at least 180 days. For organ weights and fat composition traits, 10 and 12 significant QTL locations (P<0.05), respectively, were detected on a genome-wide basis, in combined-sire or within-sire analyses. Seven QTL significant for organ weights were found at the proximal end of chromosome 2. This chromosome carries a variant myostatin allele (F94L), segregating from the Limousin ancestry, and this is a positional candidate for the QTL. Ten significant QTL for fat composition were found on chromosomes 19 and 26. Fatty acid synthase and stearoyl-CoA desaturase (SCD1), respectively, are positional candidate genes for these QTL. Two FA QTL found to be common to sire groups in both populations were for percentages of C14:0 and C14:1 (relative to all FAs) on chromosome 26, near the SCD1 candidate gene.

Mutations in the myostatin gene leading to hypermuscularity in mammals: indications for a similar mechanism in fish?

The transforming growth factor β (TGF-β) superfamily encodes secreted factors that are important in regulating embryonic development and tissue homeostatis in adults. Myostatin (MSTN, encoded by MSTN) or 'growth and differentiation factor 8', a member of this superfamily, is a negative regulator of skeletal muscle growth and is highly conserved among animal species. In 1997, a mutation associated with the so-called double-muscling phenotype in cattle was found in the MSTN gene. During the years following the discovery of the first MSTN mutation, other mutations were found in cattle and other mammalian species, and MSTN became one of the most thoroughly studied genes in animals. The aim of this review is mainly to describe the functional mutations located in the MSTN genes of several mammalian species, leading to double muscling in these animals. Furthermore, in light of the increasing importance of fish genetics, the possibility of functional mutations in piscine MSTN with a similar effect as in mammals, and a genetic model for MSTN research in fish, will also be discussed.

Polymorphisms in the ovine myostatin gene (MSTN) and their association with growth and carcass traits in New Zealand Romney sheep

Myostatin is a regulator of myogenesis and has been implicated in the regulation of adiposity and in controlling the structure and function of tendons. Polymerase Chain Reaction Single-Stranded Conformational Polymorphism (PCR-SSCP) analysis of intron-1 was used to identify five variants (designated A-E) of the myostatin gene (MSTN). The effect of this genetic variation on growth and carcass traits was investigated in 517 Romney male lambs from 17 sire-lines, born on a South Island New Zealand farm. General linear mixed effect models revealed that the presence of allele A in a lamb's genotype was associated with decreased leg, loin and total yield of lean meat, whereas the presence of allele B was associated with increased loin yield and proportion loin yield (loin yield divided by total yield expressed as percentage). The effect of the number of allele copies present was investigated, and it was found that the absence of A, or the presence of two copies of B, was associated with increased mean leg yield, loin yield and total yield. Two copies of B were also associated with a decrease in proportion of shoulder yield, whereas two copies of A were associated with a decrease in proportion of loin yield. Associations with allele C were not detected. No associations of MSTN variation with birth weight, weaning weight, pre-weaning growth rate, draft age and hot carcass weight (H-W) were detected. These results suggest that variation in ovine MSTN is associated with meat production, but not birth weight or growth rate in New Zealand Romney sheep.

The effects of a mutation in the myostatin gene on meat and carcass quality

This study examined the effects of a mutation that inactivates the myostatin gene on calving, growth, carcass and meat quality traits in South Devon cattle. This breed carries at intermediate frequency an 11-bp deletion (MH) in the myostatin gene, known to be associated with the double-muscling phenotype, thus allowing a comparison of three genotype classes. The MH allele was associated with increased calving difficulty, carcass weight, muscle conformation and ratio of polyunsaturated to saturated fatty acids, as well as with reduced growth rate, carcass and meat fatness, and desirable flavour. However, the nature of the genetic effects differed between traits: in some cases the heterozygote MH carriers were more similar to the non-carriers than to homozygote carriers and in some cases, intermediate between the two homozygotes. The direction of these genetic effects has implications for the management of this genetic variation in the South Devon and other breeds.

Quantitative analysis of performance, carcass and meat quality traits in cattle from two Australian beef herds in which a null myostatin allele is segregating

Two Australian beef cattle herds, in which selection for muscularity was a primary objective, were used in this study to identify bovine myostatin (MSTN) mutations associated with increased muscling, and to assess associations between genotype and performance, carcass and meat quality traits. One was a research herd (herd A) established from Angus × Hereford cows, and comprised a high and low muscle selection line. The other (herd B) was a commercial beef enterprise with cattle of Angus and Charolais origin. Sequencing of the MSTN coding region and flanking splice junctions in an initial sample of 34 animals from both herds identified the 821 del11 mutation as well as six other polymorphic sites. The nucleotide 374–50C > T polymorphism in intron 1 was found to be in linkage disequilibrium with the 821 del11 mutation, with both variants confined to the high muscle selection line in herd A. No other variants were exclusive to either of the two herd A selection lines. The effect of the 821 del11 mutation was further investigated in a total of 803 cattle from both herds. A relatively high prevalence of 821 del11 heterozygotes (herd A 16%; herd B 23%) was found and heterozygotes had significant advantages in eye muscle area and muscle score over their wildtype counterparts, and did not differ in meat quality. Retail beef yield from steers was higher for the 821 del11 heterozygotes from herd A (67.0 v. 63.5%) and herd B (71.8 v. 68.6%), relative to homozygous wildtype contemporaries, demonstrating the benefits of incorporating single null MSTN alleles into breeding programs.

A critical analysis of production-associated DNA polymorphisms in the genes of cattle, goat, sheep, and pig

Increasing productivity is one of the main objectives in animal production. Traditional breeding methods have led to increased gains in some traits but gains are not easily attainable in traits with low heritabilities. Exploiting the genetic variations underlying desired phenotypes is the goal of today's animal producers. Such positive genetic variants must, however, be known before possible application. Consequently, candidate genes of traits of interest have been searched for possible relationships with such traits or to explain reported quantitative trait loci (QTL) for such traits. DNA variants or polymorphisms have been identified in many such genes and their relationships with production traits determined. However, only a few genes have been evaluated, given the wealth of information on reported QTL for production traits, and in most cases genes are only partially investigated. This review presents available information on DNA variants for production traits and discusses steps that are required for effective utilization of this information for successful marker-assisted selection programs.

Limousin myostatin F94L variant affects semitendinosus tenderness

Texture parameters (peak force and compression), muscle myofibre diameter, and hydroxyproline were measured in semitendinosus samples from a cattle gene-mapping herd. The data were analysed to determine the relationships between these traits. The traits were also mapped by genetic linkage analysis to identify quantitative trait loci, and hence, candidate genes for these traits. Neither texture parameters were affected by the muscle structural traits of myofibre diameter or collagen content (as measured by hydroxyproline), despite significant variation in these traits between animals. QTL for the texture parameters of peak force and compression, as well as collagen content, were found on cattle chromosome 2 (BTA2) and attributed to the myostatin gene. Within the cattle population used for the QTL mapping, a gene variant of myostatin, F94L, has been previously shown to increase muscle mass, predominantly in the semitendinosus. It was determined herein that the F94L myostatin homozygous animals had more tender meat as measured by both peak force and compression. The variant was also responsible for a reduction in the collagen/elastin content of muscle. The myostatin F94L variant had no effect on muscle myofibre diameter of the semitendinosus, even though the variant causes substantial increases in muscle mass. Consequently, the increase in muscle mass of the variant must be due to myofibre hyperplasia and not hypertrophy. In addition, myostatin effects on tenderness are caused by changes in the extracellular matrix rather than muscle myofibre diameter.

Effects of the myostatin F94L substitution on beef traits

This study investigated the effects of a SNP in the myostatin gene (MSTN or growth differentiation factor 8, GDF8) on birth, growth, carcass, and beef quality traits in Australia (Aust.) and New Zealand (NZ). The SNP is a cytosine to adenine transversion in exon 1, causing an amino acid substitution of leucine for phenylalanine(94) (F94L). The experiment used crosses between the Jersey and Limousin breeds, with the design being a backcross using first-cross bulls of Jersey x Limousin or Limousin x Jersey breeding, mated to Jersey and Limousin cows. Progeny were genotyped for the myostatin SNP and phenotyped in Aust., with finishing on feedlot (366 calves, over 3 birth years) and in NZ with finishing on pasture (416 calves, over 2 birth years). The effect of the F94L allele (A allele) on birth and growth traits was not significant. The F94L allele in Limousin backcross calves was associated with an increase in meat weight (7.3 and 5.9% of the trait mean in Aust. and NZ, respectively, P < 0.001), and a reduction in fat depth (-13.9 and -18.7% of the trait means on live calves (600 d) and carcasses, respectively, Aust. only, P < 0.001), intramuscular fat content (-8.2% of the trait mean in Aust., P < 0.05; -7.1% in NZ, not significant), total carcass fat weight (-16.5 and -8.1% of the trait mean, Aust. and NZ; P < 0.001 and P < 0.05, respectively). Meat tenderness, pH, and cooking loss of the M. longissimus dorsi were not affected by the F94L variant. In the Jersey backcross calves, additive and dominance effects were confounded because the F94L allele was not segregating in the Jersey dams. The combined effects, however, were significant on LM area (4.4% in both Aust., P < 0.05, and NZ, P < 0.01), channel fat (-11.7%, NZ only, P < 0.01), rib fat depth (-11.2%, NZ only, P < 0.05), and carcass fat weight (-7.1%, NZ only, P < 0.05). The results provide strong evidence that this myostatin F94L variant provides an intermediate and more useful phenotype than the more severe double-muscling phenotype caused by knockout mutations in the myostatin gene.