Double muscling

Double muscling is an overdevelopment of the musculature in the neonate. The condition is seen in various beef breeds including Charolais, Santa Gertrudis, South Devon, Angus, Belgian Blue, Belgian White, and Piedmontese. The muscles of the shoulder, back, rump, and hindquarters are separated by deep creases, particularly between the semitendinosus and biceps femoris, and between the longissimus dorsi muscles of either side. Necks of double-muscled cattle are shorter and thicker, and their heads appear smaller. Associated disorders include hypoplastic reproductive tracts, delayed reproductive age of maturity, and lengthened gestation and increased birth weights combined with dystocia. Double muscling is caused by a pair of incompletely recessive genes that result in various degrees of the condition. Succinic dehydrogenase activity is significantly decreased in affected calves.