L. L. Christian

Effects of divergent selection for leg weakness on muscle and bone characteristics in Duroc swine

The dimensions and weights of front leg muscles, tendons, and bones were determined in 44 gilts that were offspring of three Duroc lines from a five-generation divergent-selection experiment on leg weakness. Lines were low, control, and high, with the low line having the greatest leg weakness and the high-line having the least leg weakness. At a slaughter weight of approximately 118 kg, the right front leg was removed from the carcasses of 14 low-, 16 control-, and 14 high-line gilts. Each intrinsic muscle was dissected from origin to insertion, removed from the leg, and measured for total length and weight. The skeleton of the front leg was disarticulated so that each bone was freed and thoroughly cleaned of muscle remnants and connective tissue. The shoulder and elbow joints were scored for the presence of osteochondral lesions. Each bone was weighed, and various dimensional traits were measured. The model used to analyze the data included the effects of line, sire within line, and weight as a covariate. The biceps brachii muscle weight and length were significantly greater in low-line pigs than in controlor high-line pigs (P < 0.05). Collectively, the forearm extensor weights were significantly greater in low-line pigs than in controlor high-line pigs (P < 0.05). The humeral and metacarpal bones were shorter in high-line pigs than in controlor low-line pigs (P < 0.05). The head of the humerus was wider and the angle of the head of the humerus was greater in high-line pigs than in controlor low-line pigs (P < 0.05). Divergent selection for differing degrees of leg soundness in Duroc swine appears to be associated with major differences in front-leg bone and muscle lengths and weights.