Optimum standardized ileal digestible tryptophan to lysine ratio for pigs weighing 7-14 kg

The objective of the present study was to evaluate the optimum ratio of standardized ileal digestible (SID) Trp to Lys for pigs after weaning. A total of 96 female pigs were allocated to 1 of 6 diets containing 0.13, 0.15, 0.17, 0.19, 0.21, and 0.23 SID Trp:Lys, with 16 individually housed pigs/treatment The diets contained similar crude protein (154 g/kg), NE (10.5 MJ/kg), and SID Lys (10.9 g/kg). Average daily feed intake (ADFI), average daily gain (ADG), and gain to feed ratio (G:F) were determined for a 21-d period. Blood and urine samples were collected on d 8 and 15. Urea concentration in plasma and urine decreased (P < 0.001) concurrently with increasing SID Trp:Lys. The ADFI, ADG, and G:F improved (P< 0.001) with increasing SID Trp:Lys. By fitting by a curvilinear-plateau model, minimum SID Trp:Lys to support optimum ADFI, ADG, and G:F were estimated to be 0.20, 0.20, and 0.16, respectively. By fitting a broken-line model, the minimum SID Trp: Lys was estimated to be 0.18, 0.18, and 0.15 for optimum ADFI, ADG, and G:F, respectively. In conclusion, growth performance of pigs weighing 7-14 kg increased up to 0.20 SID Trp:Lys. (C) 2015 Elsevier B.V. All rights reserved.