Posters QTL ANALYSES OF BEEF MUSCLE FIBRE TYPE

Beef cattle have been selected in particular for increased growth rates and greater muscle development. The myostatin gene is responsible for the muscle hyperplasia in double muscled animals and it is also responsible in these animals for differences, during foetal development, in the relative proportions of muscle fibre types. A mutation in the myostatin gene in Limousin cattle (F94L) has been found to produce a milder form of double muscling. A whole genome scan identified a highly significant quantitative trait locus (QTL) at the proximal end of chromosome 2 in a Jersey-Limousin double backcross trial for percentage meat and percentage fat in the carcass, and also for proportions of fibre type IIb count and area in the M. longissimus. We propose that this same F94L mutation is responsible for the QTL associated with increased proportions of type IIb muscle fibres in the Jersey-Limousin crosses. A significant QTL for fibre type was also found on chromosome 13 (P<0.05).