Dietary tryptophan and threonine supply to 28 days old weaned piglets

The effects of dietary levels of tryptophan (TRP) and threonine (THR) on appetite, growth performance and faecal score were assessed in an experiment with 360 weaned piglets. Littermate male castrates and females (1:1), weaned at 28 days of age, were given free access to feed during 28 days. Six dietary treatments were studied involving two levels of Standardised Ileal Digestible (SID) THR (0.59 vs. 0.69 SID THR:LYS) each with three levels of TRP (0.16, 0.19 and 0.22 SID TRP:LYS).Increasing the level of THR depressed (P<0.03) whereas TRP addition increased (P<0.008) average daily feed intake. Average daily gain (ADG) was enhanced by TRP level (P<0.001) but was unaffected by THR. Gain:feed ratio (G:F) was improved by THR level (P<0.05). Addition of TRP tended to improve G:F (P<0.10).The best pig performance in this study was achieved by feeding 0.69 SID THR/LYS in terms of G:F and 0.22 SID TRP/LYS in terms of ADG. However, in the case of TRP supplementation ADG achieved with the highest level was not significantly different from that achieved with the medium level. It is therefore proposed that securing optimal performance of weaned pigs demands dietary ratios of THR/LYS and TRP/LYS higher than 0.59 and 0.19, respectively.