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 compared. These breeds were known to differ in lean tissue growth and body composition. The pigs were fed to maintain constant live weight of about 58 kg during eight weeks. Changes in body composition within animals during the experimental period were measured using Computer Tomography. No breed differences were found in mean daily feed energy per kg metabolic body weight, but Landrace pigs needed more feed for maintaining constant body weight during the first half, and less during the second half of the experimental period (p < 0.001). Landrace pigs mobilized significantly (p < 0.01) more body fat than Duroc pigs (6.64 versus 5.21 kg). After accounting for changes in body energy Landrace pigs had a higher maintenance requirement during the whole experimental period (p < 0.001). Reasons for breed differences in maintenance requirements are discussed and related to differences in body composition. Differences in maintenance requirements could not be explained by body composition alone.