Effect of dietary crude protein and energy content on nitrogen utilisation, water intake and urinary output in growing pigs
Valaja, J.; Siljander Rasi, H.
Agricultural and Food Science in Finland 7(3): 381-390
A digestibility and balance trial was carried out with four intact castrated male pigs (live weight 3382 kg) to study the effects of dietary crude protein and energy content on nutrient digestibility, nitrogen metabolism, water intake and urinary output. In a 4 X 4 Latin square design, four barley-oats-soya bean meal based diets were arranged 2 X 2 factorially. The corresponding factors were dietary crude protein (CP) content: high (180 g/kg CP) or low protein diet (140 g/kg CP) supplemented with free lysine, methionine and threonine; and dietary net energy content: high (1.05 feed units (FU)/kg) (feed unit=9.3 MJ net energy) or low net energy content (0.95 FU/kg). Lowering dietary CP content (mean values of 189 to 152 g/kg dry matter, respectively) by supplementation of free amino acids decreased urinary nitrogen (N) excretion by 6.9 g/day (32%) (P<0.01) with no effect on faecal N excretion. Dietary protein reduction also increased the proportion of N retained per unit intake (P<0.10) and absorption (P<0.05). Daily N retention of pigs tended to decline with reduced dietary CP content (P<0.10). Dietary energy intake had no effect on N metabolism. Water intake and urinary output of pigs was unaffected by variations in protein and energy content which may be due to limitations in change-over experimental designs. The present experiment clearly demonstrated beneficial effects of lowering dietary protein supply by free amino acid supplementation on N excretion.