A within litter comparison of muscle fibre characteristics and growth of halothane carrier and halothane free crossbreed pigs

Abstract

The influence of the halothane gene on performance, carcass composition, chemical composition of carcass fractions, and muscle fibre characteristics of M. semitendinosus (ST) was examined in 14 litters of two pigs of either NN (halothane free) or Nn genotype (heterozygous for the halothane gene) (within litter comparison). The pigs were offspring of Duroc×Piétran boars (Nn) mated to Landrace×Yorkshire females (NN). The feed intake of Nn pigs was 8% ( P<0.05) lower compared with NN pigs. Based on the carcass composition, deposition rates of muscle tissue and bones did not differ between genotypes, while the deposition rate of fat tissue was lower in Nn compared with NN pigs ( P<0.01). This resulted in increased meat content of the carcass (2.6% units, P<0.001). The cross-sectional area of type I and type II fibres was 22% ( P<0.05) and 12% ( P<0.04) larger in Nn pigs, respectively. The estimated fibre number was 9% ( P<0.05) lower in Nn compared with NN pigs due to both a reduction in the number of primary (24%, P<0.05) and secondary fibres (8%, P<0.1). The estimated amount of DNA and RNA per fibre was elevated in Nn pigs compared with NN pigs suggesting a higher rate of satellite cell proliferation and capacity for protein synthesis per fibre. There was no difference in the rate of proliferation of C2C12 myoblasts and the rate of protein turnover of C2C12 myotubes when sera from the two genotypes were compared. The present results indicate that fewer fibres accomplish muscle growth of heterozygous carrier of the halothane gene with a higher growth rate due to an increased rate of satellite cell proliferation and capacity for protein synthesis. Results on cell cultures indicate that the higher rate of muscle fibre growth in Nn pigs was due to muscle intrinsic factors, i.e., changes in muscle sensitivity and/or responsiveness to growth factors.