Tryptophan requirements of growing pigs: a dose response study

A total of 144 pigs were divided into four dietary treatment groups with increasing tryptophan:lysine ratios (apparent ileal digestible (AID) Trp:Lys 0:14, 0:17, 0:20 and 0:23 and standardized ileal digestible (SID) Trp:Lys 0:15, 0:18, 0:21 and 0:24) for 6 weeks. There were 6 replicates with 6 animals per replicate in each treatment. It was shown that increasing dietary AID Trp:Lys from 0:14 to 0:20 significantly stimulated feed intake from 1.2 to 1.6 kg/day, liveweight gain from 509 to 752 g/day and body weight at the end of the experiment from 44.2 to 56.6 kg. Feed conversion ratio was reduced from 2.49 to 2.15. AID and SID Trp:Lys requirements for maximum liveweight gain were estimated at 0.19 and 0.22 and 0.20 and 0.23 using linear plateau and quadratic models, respectively