EFFECTS OF SEX, GENOTYPE AND NUTRITION ON THE RELATIVE GROWTH OF MUSCLES IN THE PIG

Abstract

The effects of liveweight, breed, sex, diet and feeding level on muscle distribution were studied by comparing nine anatomical muscle groups dissected from the half carcasses of pigs from two studies. The first study consisted of 109 pigs representing barrows and gilts of three breed groups, fed two diets differing in energy and protein. The second study consisted of 72 barrows and gilts from two breed groups fed a low-energy diet at one of three feed levels. Animals were slaughtered at 23, 68, 91 or 114 kg liveweight. The results were compared with data from one other study. In pigs, major differentiation in muscle development appears to take place prior to 23 kg liveweight. Muscle differentiation appeared to follow functional demands. Muscles associated with mobility immediately after birth such as the distal limb muscles, developed early while those associated with greater locomotion and propulsion, such as the proximal pelvic limb muscles, developed later in life. Sex had little influence on muscle distribution between 23 and 114 kg liveweight. Proportion of abdominal muscles had apparently increased markedly prior to 23 kg liveweight and continued to be influenced by the level of feeding throughout. Breed differences in muscle distribution were observed for spinal, abdominal and distal thoracic limb muscles. Key words: Swine, muscle growth, muscle distribution