Effects of Dietary Tryptophan Supplementation and Feed Restriction on Growth Performance and Carcass Characteristics of Goslings

The effects of dietary levels of tryptophan and feeding regimen on growth performance and carcass characteristics were evaluated in Yangzhou goslings from 28-70 days of age. In a 2x3 factorial design, a total of two hundred and seventy birds were randomly assigned to 6 treatments according to a 2x3 factorial design. Treatments consisted of two feeding regimens ens (ad libitum vs. 90% restricted feeding) each contained three levels of tryptophan (0.15, 0.23 and 0.31%) to which 0.08% increments of tryptophan were supplemented. Each experimental treatment had 3 replicates of 15 birds per pen. Feed intake of goslings from each pen was recorded everyday during the 6th week while body weight and feed conversion ratio were measured at a 2 weeks interval. At the end of the feeding experiment, 9 goslings (three birds were randomly chosen from each replicate) were slaughtered to evaluate carcass characteristics. The results showed that average daily gain and carcass characteristics were significantly higher in goslings fed ad libitum when comparing with those restricted feeding. Positive responses in daily feed intake and weight gain were attained by the addition of tryptophan to level up to 0.23% in diet whereas no statistical difference was found when the dietary level reached 0.31%. Supplemental tryptophan had not significant effect on carcass characteristics with exception of breast meat yield. It was found that goslings maximized their breast meat yield at a dietary level of 0.23% tryptophan compared with 0.15% tryptophan in diet. This study indicated that the gosling diets fed in restriction have some unfavourable effects on growth performance and carcass characteristics. Dietary tryptophan addition up to level 0.23% can increase daily feed intake, weight gain and breast meat yield.