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

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 containin g 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 ea ch 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 n ot 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 rectili near model, which had a linear ascending phase (PD = 4.84 +/- 1.948L, R-2 = 0.935, P = 0.002) and a horizontal component representing maximum protein deposition rate of 32.3 g/day, revealed that maximum protein deposition occ urred at 14.1 g lysine/kg. The quadratic function (PD = -2.74 + 3.74L - 0.0 99L(2), R-2 = 0.916, P = 0.003) provided an estimate of the lysine requirem ent of 14.9 g lysine/kg occurring at a point where PD reached 95% of the ma ximum protein deposition rate (32.5 g/day). Use of an asymptotic model (PD = 32.60 - 186 x 0.727L, R-2 = 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 prot ein deposition rate (32.6 g/day). These data indicate that early weaned pig s should be fed a highly digestible diet containing 14-15 g lysine/kg to ma ximise protein deposition.