OXIDATION OF SUBSTRATES AND LIPOGENESIS IN PIGS (SUS-SCROFA), MINK (MUSTELA-VISON) AND RATS (RATUS-NORVEGICUS)

Data from experiments with 25 growing pigs at high feeding level, with 12 adult mink on a varied energy supply and with 36 rats on a mainten ance level were used in a biological model of nutrient oxidation, lipo genesis and retention at the whole body level. Nutrient oxidation was calculated from gas-exchange measurements in respiration chambers work ing according to indirect calorimetry principles. Lipogenesis and nutr ient retention were measured by means of carbon and nitrogen balances, in accordance with the demonstrated model. The results demonstrated t hat growing pigs had a high level of protein retention and low protein oxidation. Digested carbohydrates were oxidized or used for lipogenes is. Oxidation of carbohydrate was the main energy sourer, while lipoge nesis was the main source of fat retention. Independent of dietary fat level, pigs did not oxidize fat but used all dietary fat for body fat retention. The mink, being fed with high protein and fat levels but o nly a small amount of carbohydrate, use protein and fat as their main energy sources. Rats fed near-maintenance level used dietary carbohydr ate as a main substrate for oxidation. It was demonstrated that the pr esent model of nutrient oxidation, lipogenesis and retention in differ ent animal species and at different dietary composition can be quantif ied by means of indirect calorimetry and measurements of carbon and ni trogen balances. (C) 1998 Elsevier Science B.V.