On the genetic determinism of muscular hypertrophy in the Belgian White and Blue cattle breed. II. Population data

Abstract

The inheritance of muscle hypertrophy has been studied in an experiment where Fi cows (Belgian Blue X Friesian) are backcrossed to Belgian Blue sires. The total weight of the most important muscles, in calves slaughtered at the constant weight of 84 kg, was the criterion for muscle development. The distribution of this variable in the backcross shows a clear bimodality corresponding to the segregation of 2 alleles, in equal proportions. The fitting of a monogenic model, by the Weighted Least Squares method, has led to the estimations of gene effect and dominance deviation. The difference between the 2 homozygotes amounts to more than 6 times the standard deviation within genotype. It is concluded that a major gene is involved in the determination of muscle hypertrophy in the Belgian Blue cattle breed and that regarding the phenotypic expression considered in this study this gene behaves as a partially recessive gene, the heterozygote being near the homozygous normal. The symbol mh for muscular hypertrophy is proposed to identify this major gene.