Variation in the ovine MYF5 gene and its effect on carcass lean meat yield in New Zealand Romney sheep

Relationship between the expression levels of myogenic regulatory factor genes and carcass characteristics in Kivircik and Hungarian Merino lambs

This study aimed to investigate the expression profiles of the myogenic regulatory genes MYOD1, MYOG, MYF5, MYF6, and MSTN in longissimus dorsi muscle, as well as the correlation of the expression levels of these genes with carcass characteristics and growth performance in the Kivircik and Hungarian Merino sheep breeds. The expression levels of the MYF5, MYF6, and MYOG genes were found to be significantly correlated with the rib proportion, the expression level of the MYOG gene was identified as being the main determinant of variations in the rib proportion in the Kivircik lambs. The regression analysis results revealed that the expression levels of the MYF5 and MSTN genes played an essential role in determining the cold carcass dressing percentage in Hungarian Merino lambs. Further, as a result of the regression analysis, the model including the expression level of the MYF6 gene demonstrated that this gene could be responsible for 36.4% of the differences observed in cold carcass weight. In conclusion, the findings of this study suggest that the expression levels of the MYF5, MYF6, and MYOG genes were associated with various carcass traits, particularly in the Kivircik breed, and these genes hold potential as markers for enhancing breed productivity.

A Genomic and Phenotypic Investigation of Feed Efficiency and Growth Traits in Targhee and Rambouillet Sheep

The U.S. range sheep industry uses estimated breeding values (EBVs) as part of their breeding objectives to increase post-weaning weight. The study objective was to quantify the relationship between lamb growth EBVs, feed intake, and feed efficiency. Eighty-one range ewe lambs were enrolled in the study to measure residual feed intake (RFI) over two 42-d periods at both the weaning and yearling stages. The ewe lambs' post-weaning weight EBVs (PWWT EBVs) were linearly associated with their phenotypic traits. Preliminary genome wide associations (GWAs) were also performed with Dry Matter Intake (DMI), RFI, mid-test body size, and average daily gain (ADG) and Ovine 50K SNP genotypes. Post-weaning weight EBVs were associated with dry matter intake (DMI) (p < 0.05) but had no association with residual feed intake (RFI) (p > 0.05) in both experimental periods. However, PWWT EBV was predictive of mid-test body weight in both periods (p < 0.05). A single SNP at Oar2:68,812,505, located within DMRT2, was associated with DMI and RFI in the second experimental period (Bonferroni corrected p <0.05). While selecting for higher post-weaning weight range ewes may increase feed consumed due to a larger body size, it was not associated with feed efficiency.

Novel Single Nucleotide Polymorphisms and Haplotype of MYF5 Gene Are Associated with Body Measurements and Ultrasound Traits in Grassland Short-Tailed Sheep

Myogenic factor 5 plays active roles in the regulation of myogenesis. The aim of this study is to expose the genetic variants of the MYF5 and its association with growth performance and ultrasound traits in grassland short-tailed sheep (GSTS) in China. The combination technique of sequencing and SNaPshot revealed seven SNPs in ovine MYF5 from 533 adult individuals (male 103 and female 430), four of which are novel ones located at g.6838G > A, g.6989 G > T, g.7117 C > A in the promoter region and g.9471 T > G in the second intron, respectively. Genetic diversity indexes showed the seven SNPs in low or intermediate level, but each of them conformed HWE (p > 0.05) in genotypic frequencies. Association analysis indicated that g.6838G > A, g.7117 C > A, g.8371 T > C, g.9471 T > G, and g.10044 C > T had significant effects on growth performance and ultrasound traits. The diplotypes of H1H3 and H2H3 had higher body weight and greater body size, and haplotype H3 had better performance on meat production than the others. In addition, the dual-luciferase reporter assay showed that there are two active regions in the MYF5 promoter located at −1799~−1197 bp and −514~−241 bp, respectively, but g.6838G > A and g.7117 C > A were out of the region, suggesting these two SNPs influence the phenotype by other pathway. The results suggest that the MYF5 gene might be applied as a promising candidate of functional genetic marker in GSTS breeding.

Variants in myostatin and MyoD family genes are associated with meat quality traits in Santa Inês sheep

Myostatin and MyoD family genes play vital roles in myogenesis and this study aimed to identify association of variants in MyoD1, MyoG, MyF5, MyF6, and MSTN genes with meat traits in Santa Inês sheep. A dataset with 44 variants and records of seven meat traits in 192 lambs (pH0, pH24, a*, b*, L*, tenderness assessed by shear force, and water-holding capacity) was used. Single-locus and haplotype association analyses were performed, and the significance threshold was established according to Bonferroni's method. Single-locus analysis revealed two associations at a Bonferroni level, where the variant c.935-185C > G in MyoD1 had an additive effect (-4.31 ± 1.08 N) on tenderness, while the variant c.464 + 185G > A in MyoG had an additive effect (-2.86 ± 0.64) on a*. Additionally, the haplotype replacement GT>AC in MSTN was associated with pH0 (1.26 ± 0.31), pH24 (1.07 ± 0.27), a* (-1.40 ± 0.51), and tenderness (3.83 ± 1.22 N), while the replacement GT > AG in MyoD1 was associated with pH0 (1.43 ± 0.26), pH24 (1.25 ± 0.22), b* (-1.06 ± 0.39), and tenderness (-4.13 ± 1.16 N). Our results have demonstrated that some variants in MyoG, MyF6, MyoD1, and MSTN can be associated with physicochemical meat traits in Santa Inês sheep.

Genetics of Omega-3 Long-Chain Polyunsaturated Fatty Acid Metabolism and Meat Eating Quality in Tattykeel Australian White Lambs

Meat eating quality with a healthy composition hinges on intramuscular fat (IMF), fat melting point (FMP), tenderness, juiciness, flavour and omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) content. These health-beneficial n-3 LC-PUFA play significant roles in optimal cardiovascular, retinal, maternal and childhood brain functions, and include alpha linolenic (ALA), eicosapentaenoic (EPA), docosahexaenoic (DHA) and docosapentaenoic (DPA) acids. The primary objective of this review was to access, retrieve, synthesise and critically appraise the published literature on the synthesis, metabolism and genetics of n-3 LC-PUFA and meat eating quality. Studies on IMF content, FMP and fatty acid composition were reviewed to identify knowledge gaps that can inform future research with Tattykeel Australian White (TAW) lambs. The TAW is a new sheep breed exclusive to MARGRA brand of lamb with an outstanding low fat melting point (28-39°C), high n-3 LC-PUFA EPA+DHA content (33-69mg/100g), marbling (3.4-8.2%), tenderness (20.0-38.5N) and overall consumer liking (7.9-8.5). However, correlations between n-3 LC-PUFA profile, stearoyl-CoA desaturase (SCD), fatty acid binding protein 4 (FABP4), fatty acid synthase (FASN), other lipogenic genes and meat quality traits present major knowledge gaps. The review also identified research opportunities in nutrition-genetics interactions aimed at a greater understanding of the genetics of n-3 LC-PUFA, feedlot finishing performance, carcass traits and eating quality in the TAW sheep. It was concluded that studies on IMF, FMP and n-3 LC-PUFA profiles in parental and progeny generations of TAW sheep will be foundational for the genetic selection of healthy lamb eating qualities and provide useful insights into their correlations with SCD, FASN and FABP4 genes.

Association analysis of the ovine KAP6-1 gene and wool traits in Barki sheep

Traditionally, sheep are raised in Egypt for meat and wool production. Selection for higher wool quality could increase its suitability for particular processing procedures in the wool industry, which maximizes the profit of the sheep production enterprise. In this research, the effect of genetic polymorphisms of the keratin-associated protein 6-1 (KAP6-1) on wool traits was investigated in Barki sheep. Animals were genotyped by polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP). Results identified a single nucleotide polymorphism (rs589531301, G > C) with three genotypes (GG, GC and CC) and the genotypic frequencies were 14.63, 43.82 and 41.55%, respectively. The KAP6-1 genotypes significantly (p > 0.05) affected greasy fleece weight (GFW; p = 0.05), prickle factor (PF; p = 0.02), staple length (SL; p = 0.038), fiber diameter (FD; p = 0.015), kemp score (KS; p = 0.048), greasy color grade (GCG; p = 0.037), luster grade (LS; p = 0.048) and the greasy structure (GS; p = 0.038). The noteworthy, animals with the CC genotype produce more wool (GFW = 1.116 kg) with longer SL (9.03 cm), finer wool (FD = 24.34 μm) and higher KS compared to other genotypes. The results of this report presented the KAP6-1 gene as a candidate gene to improve the wool production traits in the Egyptian Barki sheep and worldwide.

Identification of Caprine KRTAP28-1 and Its Effect on Cashmere Fiber Diameter

The keratin-associated proteins (KAPs) are constituents of cashmere fibers and variation in many KAP genes (KRTAPs) has been found to be associated with fiber traits. The gene encoding the high-sulphur KAP28-1 has been described in sheep, but it has not been identified in the goat genome. In this study, a 255-bp open reading frame on goat chromosome 1 was identified using a search of similar sequence to ovine KRTAP28-1, and that would if transcribed and translated encode a high sulphur KAP. Based on the analysis of polymerase chain reaction (PCR) amplicons for the goat nucleotide sequences in 385 Longdong cashmere goats in China, five unique banding patterns were detected using single-stranded conformational polymorphism (SSCP). These represented five DNA sequences (named variants A to E) and they had the highest resemblance to KRTAP28-1 sequences from sheep, suggesting A-E are variants of caprine KRTAP28-1. DNA sequencing revealed a 2 or 4-bp deletion and eleven nucleotide sequence differences, including four non-synonymous substitutions. Of the four common variants (A, B, C and D) found in these goats, the presence of variant A was associated with decreased mean fiber diameter and this effect appeared to be additive. These results indicate that caprine KRTAP28-1 variation might have value as a molecular marker for reducing cashmere mean fiber diameter.