Polymorphism of CAST and GDF-8 genes and association with physical-chemical parameters of sheep meat
In Brazil, most sheep are of the Santa Inês breed, which shows rusticity in breeding and grazing systems, being able to offer better adaptation characteristics for animals with meat production ability, such as the Texel and Dorper sheep. They can also improve meat production in animals that have better characteristics for milk production, such as Lacaune and East Friesian breeds. We investigated the polymorphisms of calpastatin (CAST) and myostatin (GDF8) genes and their association with meat quality parameters of 84 lambs, including: 14 purebred Santa Inês and 70 crossbred animals of five genetic groups: 16 animals (½ Santa Inês x ½ Black Dorper); 12 animals (½ Santa Inês x ½ White Dorper); 19 animals (½ Santa Inês x ½ Texel); 14 animals (½ Santa Inês x ½ Lacaune); and 9 animals (½ Santa Inês x ½ East Friesian). To evaluate the polymorphism of the genes we used PCR and Simple Chain Conformation Polymorphism (SSCP) with DNA sequencing to determine where base exchange occurred in the gene sequences. The PCR-SSCP technique detected four bands of the CAST gene and three of the GDF-8 gene. In meat quality of sheep there was only one different breed group by Shear force with less value than Santa Ines breed group. The CAST gene had four genotypes with two single nucleotide polymorphisms (SNPs) (c.679A> G; c.383A> G), which resulted in the exchange of glutamic acid by glycine and threonine by alanine, which impacted pH values. Reduced pH values for BB and AB genotypes, and increased pH value in the AA genotype were found. Three genotypes of the DGF-8 gene with three SNPs were identified with changes of A-T, A-G, and T-G, influencing color hue angle (h*). After 10 days post mortem, there was an increase in hue angle the highest values were found for genotypes DF and DE. The polymorphisms of the CAST gene and in the promoter region of the GDF-8 gene influence meat color and final pH, affecting meat quality in various of the sheep breed groups.