[Regulation of energy balance and body weight during isoenergetic carbohydrate and fat supply in a long-term study in sows].

A respiration trial was conducted in 14 adult sows to investigate the energetic effects of a high carbohydrate and a high fat diet over a period of 21 weeks. The basal ration was mainly based on barley and soybean meal and covered 60% of the maintenance requirement for energy. The addition of starch (50% wheat starch, 50% maize starch) or fats (25% lard, 25% soybean oil, 50% olive oil) was 173 kJ/kgW0.75. All rations were calculated with reference to the initial weight of the sows and remained constant throughout the experiment. The animals were fed twice daily. Feces and urine were collected during the first and last part of the experiment over six days each. Forty eight hour measurements of the gas exchange were recorded five times in the course of the trial. Energy balances were calculated using an indirect calorimetry technique (RQ method) as well as the carbon nitrogen balance technique. All components of the energy balance (feces energy, urine energy, metabolizable energy, energy retention) showed no significant difference between the two treatments. The heat production of the animals was 413 +/- 31 with the starch diet and 412 +/- 36 kJ/kg W0.75 when the fat diet was fed. The mean weekly body weights of both treatment groups coincided in all phases of the experiment. Calculation of nutrient oxidation performed for diets and for animal metabolism revealed that only the carbohydrate balance was achieved, whereas the fat balance showed unrealistic results. The sensitivity of the nutrient balance method to measurement errors of the gas exchange has been discussed. The current results indicate that an equal supply of starch or fat energy acts identically in the long-term on body weight regulation and energy balance when overfeeding is not present.