Characteristics associated with a naturally occurring mutation of the callipyge gene in sheep are presented. Assignment of the callipyge locus to the telomeric region of ovine chromosome 18 was confirmed and an unusual mode of expression was verified. Heterozygotes (CN) receiving the mutant C allele from the sire and the wildtype N allele from the dam expressed extreme muscularity, whereas NC heterozygotes were of normal phenotype, that is, reciprocal heterozygotes produced different phenotypes. Furthermore, both homozygous genotypes (CC and NN) produced normal phenotypes. Callipyge lambs had greater dressing percentage, deposited lean tissue more rapidly and fat tissue less rapidly, and produced compact 25.67 kg carcasses with 71.9% lean compared to 64.4% carcass lean for normal lambs. Callipyge loin chops had less marbling and greatly increased shear force values, associated with evaluated levels of postmortem calpastatin activity. Despite the significant beneficial effects of the mutant callipyge allele, the detrimental effects on various meat quality traits must be circumvented before the allele can be exploited by the sheep industry.

K. A Leymaster, B. A Freking

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 24: Sheep and goats (fibre); sheep and goats (meat and milk); poultry; horses; buffaloes., , 109–116, 1998
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