NOTE ABOUT CALCULATION OF OXIDATION OF NUTRIENTS IN PIGS

A method for calculating the amount of oxidized nutrients was evaluated from gas exchange measurements with young pigs in which the respiratory quotient was below 1.0. The material included 23 barrows of Danish Landrace (20-25 kg LW), fed different feed compounds on two feed levels, and measured individually in 7-days balance periods. A 24 hours measurement of gas exchange in an open-air-circuit respiration unit was placed in the middle of each balance period. The heat production from oxidation of different nutrients in relation to total heat production was about 10% for protein and 70-77% for carbohydrate, depending of feed levels. The heat from oxidation of fat was highest on the low feed level, with 22%, caused by a higher mobilization of fat from the body. The amount of oxidized carbohydrate and fat calculated from the gas exchange were close to the values of digested carbohydrate and fat, including fat from the body, indicating that the method gives reliable description of substrate oxidation in growing pigs.