QUANTITATIVE PARTITION OF PROTEIN CARBOHYDRATE AND FAT POOLS IN GROWING PIGS

A model combining data from balance experiments with data From oxidati on of nutrients demonstrating the pools of protein, carbohydrate and F at and their partition in the body was presented. Data from more than 200 experiments with growing pigs were used to fill up the ''black box es'' in the model and to discuss the pattern between catabolic and ana bolic processes of the different nutrients. With a ME-intake of 1.3 MJ /kg(0.75) the proportion of retained protein from the protein pool var ied from 50 to 75% depending on the age of animals and the protein qua lify. At a low protein intake and ME of 0.6 MJ/kg(0.75) th, utilizatio n of protein was reduced to about 25% as a substantial part of the pro tein pool was oxidized. The carbohydrate group from the protein source s constituted less than 5% of the carbohydrate pool. The oxidation of carbohydrates was between 50-75% of the pool in all experiments, while the rest was used for lipognesis. Even on a low feeding level the pat tern occurred indicating a requirement for specific substances formed in the body. Lipogenesis constituted 46-96% of the fat pool depending of the amount on digested fat in the different experiments, No oxidati on of fat was observed in experiments with pigs (30-90 kg LW) on a hig h feeding level in spite of the broad variation in the amount of diges ted fat, indicating a complete storage of the fat pool into body fat, in experiments with piglets (3-9 kg LW) on the same energy intake fat oxidation of about 30% occurred, probably caused by the high energy re quirement of the piglets. With a ME-intake of 0.6 MJ/kg(0.75) the oxid ation of fat was higher than the fat pool for pigs between 30-60 kg LW , thereby causing oxidation of body fat to cover the energy requiremen ts.