Double muscling

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Characteristic double muscling in a Belgian Blue bull

Double muscling is a genetic disease characterised by enlarged skeletal musculature.

This feature of genetic modification, reported in Belgian Blue, Piemontese, Blonde d'Aguitaine[1] and Devon breeds, is induced by modification of the myostatin gene (muscular hypertrophy gene)[2], known to be associated with the double-muscling phenotype[3]. This results in a disturbed metabolism of trans-18:1 and conjugated linoleic acids and muscle over-replication[4].

Clinically affected cattle have grossly enlarged musculature, with double-muscled cattle possessing nearly twice the number of muscle fibres at birth than normal cattle[5]. Affected cattle also have reduced exercise and heat tolerance, delayed-onset puberty, reduced fertility due to an increased incidence of mortality in double-muscled embryos, increased incidence of dystocia, reduced milk production and increased calf mortality.


  1. Grisolia AB et al (2009) Myostatin (GDF8) single nucleotide polymorphisms in Nellore cattle. Genet Mol Res 8(3):822-830
  2. Martínez A et al (2010) Effect of breed body size and the muscular hypertrophy gene in the production and carcass traits of concentrate-finished yearling bulls. J Anim Sci 88(4):1229-1239
  3. Wiener P et al (2009) The effects of a mutation in the myostatin gene on meat and carcass quality. Meat Sci 83(1):127-134
  4. Aldai N et al (2010) Double-muscling character influences the trans-18:1 and conjugated linoleic acid profiles in concentrate-fed yearling bulls. Meat Sci 85(1):59-65
  5. Oldham JM et al (2001) Molecular expression of myostatin and MyoD is greater in double-muscled than normal-muscled cattle fetuses. Am J Physiol Regul Integr Comp Physiol 280(5):R1488-R1493