Energy metabolism and substrate oxidation in pigs during feeding, starvation and re-feeding

Energy metabolism and substrate oxidation was measured in 12 growing pigs by means of indirect calorimetry and nutrient balances. The measurements were carried out during 5 days of feeding followed by 4 days of starvation and 5 days of re-feeding. During the feeding period, dietary carbohydrates were the main energy source, sufficient to cover energy requirements without oxidation of fat. Starvation reduced the total heat production and affected the oxidation pattern by reducing protein oxidation and shifting from carbohydrate to fat oxidation. On the second day of starvation, the main energy source was body fat and there was no oxidation of carbohydrate. On the second day of re-feeding, the heat production reached the same level as during the feeding period. Also, during the second day of re-feeding, the pattern of nutrient oxidation was similar to the feeding period with oxidation of carbohydrate providing 90% and oxidation of protein providing 10% of the total heat production. There was no fat oxidation. The results demonstrated that the growing pigs were able to re-establish oxidative patterns already 2 days after re-alimentation.