Histological characteristics of longissimus dorsi muscle and their correlation with restriction fragment polymorphisms of calpastatin gene in F2 Jinghua3 Piétrain crossbred pigs

In order to evaluate the genotype of the calpastatin (CAST) gene and its relationship to muscle histology and other post mortem traits in the Jinhua3 Piétrain F2 pig family, 158 barrows and gilts were electrically stunned and exsanguinated. Both blood and muscle samples were collected, and both post mortem traits and meat qualities were recorded. Restriction fragment length polymorphism (RFLP) analysis, the periodic acid Schiff reaction (PAS) and myosin heavy-chain immunohistochemistry were employed to explore the relationship between genotype and muscle histology. Based on PAS reactivity, muscle fibres can be classified into three types: PAS (2), PAS (1) and PAS (11). Myosin heavy-chain immunohistochemistry can differentiate muscle fibres into either slow or fast fibres; the proportion of slow and fast fibres were 6% and 94%, respectively. When the amplification products of the CAST gene were digested with MspI, HinfI and RsaI, two different cleavage patterns could be discriminated from the endonuclease map detected using each enzyme. The results showed that the polymorphisms detected using these three endonucleases are identical. Only three genotypes (AA/CC/EE, AB/CD/EF and BB/DD/FF) were distinguished. Their frequencies were 0.1835, 0.5823 and 0.2342, respectively. Different genotypes had significant association with area and pH45m value of loin muscle, while showing no significant association with the water-holding capacity and conductivity of loin muscle. The results also revealed that the genotypes had a significant correlation with diameter, area, circularity and the aspect ratio of muscle fibres. It was also presented that the genotypes significantly correlated with the percentage of intramuscular connective tissue.