[Energy balance study with a carbohydrate-free protein-fat diet]

The effect of a carbohydrate-free protein-fat (PF) diet compared with a mixed diet (CPF diet) on the energy metabolism was studied in a changeover trial with mature sows. The PF diet contained two thirds of its metabolizable energy as protein and one third as fat; in the CPF diet the relationship was 3.5 carbohydrate: 1 protein: 0.2 fat. Under the conditions of undernutrition and neutral temperature nitrogen, carbon and energy balance were assessed as parameters according to the procedures of indirect calorimetry in four 24-hour measurements each for the gaseous exchange of the animals. At isocaloric supply of metabolizable energy, no differences were found in the N, C and energy retention. The mean heat production amounted to 23.6 MJ/day in both dietary groups. Also, no dietary influence could be observed with regards to the daily time pattern of heat production nor to the physical activity of the animals. Computation of the nutrient utilization on the basis of potential ATP formation resulted in a turnover of 304 mol ATP/day for the mixed diet and in 275 mol ATP for the carbohydrate-free diet. The discrepancy is discussed. Overall, the results show that an increased heat production, providing the possibility of an augmented loss of body energy, could not be induced by the carbohydrate-free protein-fat diet in the course of undernutrition.