Dietary lysine requirements of heavy and light pigs weaned at 14 days of age

Abstract

Seventy 14-day-old male pigs that were either heavy (6.0 kg) or light (3.6 kg) for age were weaned into individual pens and fed 1 of 7 diets containing 9.2–21.0 g lysine/kg feed in a study designed to determine the effect of dietary lysine and weight on lysine requirements of pigs. Five pigs from each weight group were used to determine initial body composition. When pigs reached 10 kg they were slaughtered and empty body composition was analysed to determine protein tissue accretion rates. Protein deposition rate was not affected by weight at weaning but increased with dietary lysine content before reaching a plateau. The relationship between protein deposition (PD, g/day) and dietary lysine (L, g/kg) was described by 3 models. The rectilinear model, which had a linear ascending phase (PD = 4.84 + 1.948L, R² = 0.935, P = 0.002) and a horizontal component representing maximum protein deposition rate of 32.3 g/day, revealed that maximum protein deposition occurred at 14.1 g lysine/kg. The quadratic function (PD = – 2.74 + 3.74L – 0.099L² , R² = 0.916, P = 0.003) provided an estimate of the lysine requirement of 14.9 g lysine/kg occurring at a point where PD reached 95% of the maximum protein deposition rate (32.5 g/day). Use of an asymptotic model (PD = 32.60 – 186 0.727L, R² = 0.919, P = 0.003) provided an estimate of 14.9 g lysine/kg occurring at a point where PD reached 95% of the maximum protein deposition rate (32.6 g/day). These data indicate that early weaned pigs should be fed a highly digestible diet containing 14–15 g lysine/kg to maximise protein deposition.