EFFECTS OF ENFORCED EXERCISE ON GROWING PIGS: FEED INTAKE, RATE OF GAIN, FEED CONVERSION, DISSECTED CARCASS COMPOSITION, AND MUSCLE WEIGHT DISTRIBUTION

The effects of enforced exercise on performance and carcass composition of growing pigs were studied on eight crossbred gilts. Four animals were exercised periodically on a treadmill from a liveweight of 12 to 60 kg; the remaining four animals acted as a control group. Pigs were exercised three afternoons a week for a period of 60 min at a speed of 2 km/h. Animals were slaughtered at a liveweight of 60 kg and the left side of each carcass dissected into individual muscles, fat and bone. Proximate analyses were conducted on two selected muscles. There were no significant differences between the groups overall (0 to 9 wk) in feed intake, weight gain or efficiency of feed conversion. From 7 to 9 wk the exercised group grew at a significantly faster rate and consumed significantly less feed per kg liveweight than the control group. The enhanced rate of gain of the exercised group during this period occurred even though feed intakes of the two groups were similar. It is suggested that this improved gain may have been due to a compensatory growth effect associated with a relative decrease in the severity of the exercise treatment as the pigs increased in size. Exercise treatment had no significant effects on carcass weight or on the weight of the following organs: blood, heart, liver, kidneys, spleen, alimentary tract tissue and alimentary tract fat. Similarly, enforced exercise had no significant effects on either the proportion of carcass muscle, fat and bone or on muscle distribution. Chemical analysis of M. psoas major from exercised animals showed a significantly higher protein and lower moisture content, respectively, than those from control animals. Composition of M. biceps brachii in exercised and control animals was similar.