Breed and sex differences in equally mature sheep and goats 3. Muscle weight distribution

Abstract

ABSTRACTMales and females from Soay, Welsh Mountain, Southdown, Finnish Landrace, Jacob, Wiltshire Horn and Oxford Down sheep breeds and a breed of feral goats were slaughtered when they reached 0·40, 0·52, 0·64 or 0·76 of the mean mature body weight of their breed and sex. Total weight of dissected muscle was close to 0·30 times fleece-free empty body weight, or 0·24 times live weight, for all breeds and stages of maturity. The growth of 12 individual muscles or muscle groups dissected from the commercially higher-valued joints of the carcass, was examined in relation to live weight and total muscle weight. Limb muscles matured early. All 12 muscles, when combined, also matured early so that the proportion of lean tissue from the higher-valued joints declined as live weight increased.There were small but significant sex differences in the relative growth rate of some muscles. The abdominal muscles were early maturing for males and average for females. There were also sex differences in muscle weight distribution. The proportion of muscle in the hind limb of females was 1·055 times that in males, while the 12 muscles from higher-valued cuts constituted 0·403 of total carcass muscle for females and 0·389 for males, a proportional difference of 0·035.Muscle weight distribution was unrelated to breed size with the possible exception of m. gastrocnemius which appeared to be relatively smaller in genetically larger breeds. After accounting for differences in mature weight, there remained small but significant breed deviations in muscle weight distribution. Southdowns had the most attractive distribution. Feral goats and Jacob sheep, although they had the highest proportion of total muscle, had a much less attractive distribution.