Estimation of net nutrient oxidation and lipogenesis in growing pigs.

Data from previous series of trials were reevaluated in order to quantify the net nutrient oxidation and lipogenesis by combining data from balance experiments and indirect calorimetry measurements. The experiments were carried out with eight castrated males of Danish Landrace measured individually from 30 to 100 kg BW. All pigs were fed alternately on high feeding level, near ad libitum and on low feeding level, near maintenance. Oxidation of carbohydrate (OXCHO) and fat (OXF) was calculated from gas exchange measurements. On high feeding level the contribution from OXCHO and OXF to the total heat production was 55 and 30%, respectively, at 30 kg BW and fairly constant from 60 kg BW with OXCHO around 80% and no net OXF. At low feeding level the contribution from OXCHO and OXF was 28 and 63%, respectively, at 30 kg BW, increasing to 52% for OXCHO and decreasing to 37% for OXF at 95 kg BW. The lipogenesis on high feeding level increased from 2.4 to 11.9 MJ/d, while on low feeding level it increased from 2.5 to 3.6 MJ/d at 30 to 95 kg BW. The intake of carbohydrate was too low to cover energy requirement by OXCHO on low feeding level and in the first periods on high feeding level and OXF occurred. In spite of a deficit of carbohydrate for oxidation a part of carbohydrate (2.6 MJ/d, approximately 150 g/d) was used for fat synthesis, indicating an importance of lipogenesis in growing pigs.