Performance and utilization of dietary energy and amino acids in piglets fed low protein diets

Abstract

A total of 32 Piétrain×(Landrace×Large White) barrows were used to test the effect of reducing the dietary crude protein (CP) level on performance and composition of gain in piglets from 12 to 27 kg. Four diets based on corn, wheat, barley and soybean meal providing 1.01 g of ileal digestible lysine per MJ of NE (net energy) were prepared. Diet 1 was formulated without free amino acids (AA), while in diets 2–4, CP level was progressively reduced and free AA were supplemented according to the ideal protein concept. The CP levels were 224, 204, 184, 169 g/kg for diets 1, 2, 3 and 4, respectively. Piglets were housed individually and had free access to feed and water. The feed intake was measured daily. At the end of the experiment, animals were slaughtered and body composition was measured. The 12 control piglets were slaughtered at the beginning of the experiment and the composition of gain (water, ash, protein lipid, AA and energy) was calculated according to the comparative slaughter technique. Feed intake was the lowest ( P<0.05) with diet 1 (959 g/day) and similar for diets 2–4 (1049 g/day, on average). Nevertheless, average daily gain of the animals did not differ between treatments (666 g/day, on average). Reducing CP level resulted in a numerically reduced water consumption and urine production, but no effect on the occurrence of diarrhea was observed. The N excretion over the total experiment was reduced by 42% from diet 1 to diet 4. At identical ME (metabolizable energy) intakes (2.52 MJ/day per kg BW 0.60), protein and lipid composition of gain (18.9 and 13.0 g/day per kg BW 0.60, on average) were not affected by the diet. Energy gain (0.94 MJ/day per kg BW 0.60) and heat production (1.58 MJ/day per kg BW 0.60) were also not different between treatments. The amino acid pattern of deposited protein was not affected by dietary CP level, except that histidine deposition was significantly smaller with diets 3 and 4. These results indicate that a reduction of dietary CP level by up to 55 g/kg in association with adequate AA supplementation does not affect the level of performance and body composition of piglets and contributes to lower N excretion.