BREED DIFFERENCES IN MAINTENANCE REQUIREMENTS OF GROWING PIGS WHEN ACCOUNTING FOR CHANGES IN BODY-COMPOSITION

To study genetic variation in maintenance requirements of growing pigs , two breeds, Norwegian Landrace and Duroc of Canadian origin, were co mpared. These breeds were known to differ in lean tissue growth and bo dy composition. The pigs were fed to maintain constant live weight of about 58 kg during eight weeks. Changes in body composition within ani mals during the experimental period were measured using Computer Tomog raphy. No breed differences were found in mean daily feed energy per k g metabolic body weight, but Landrace pigs needed more feed for mainta ining constant body weight during the first half, and less during the second half of the experimental period (p < 0.001). Landrace pigs mobi lized significantly (p < 0.01) more body fat than Duroc pigs (6.64 ver sus 5.21 kg). After accounting for changes in body energy Landrace pig s had a higher maintenance requirement during the whole experimental p eriod (p < 0.001). Reasons for breed differences in maintenance requir ements are discussed and related to differences in body composition. D ifferences in maintenance requirements could not be explained by body composition alone.