Effects of dietary threonine on growth performance and carcass traits of Yangzhou geese

A dose-response experiment with 5 total dietary threonine (Thr) levels (0.54, 0.64, 0.74, 0.84 and 0.94%) was conducted to study the effect of dietary Thr on growth performance and carcass traits of Yangzhou geese from 0 to 8 weeks of age. Three hundred 1-day-old Yangzhou goslings were randomly allocated to 15 pens with 20 birds (10 males and 10 females) per pen according to similar pen weight. There were 5 dietary treatments, consisting of 3 replicate pens. Weight gain, feed intake and feed/gain of geese from each pen were measured at 2-week intervals from 0 to 8 weeks. At 56 days of age, four geese (2 males and 2 females) were selected randomly from each pen and slaughtered to evaluate the carcass quality. The results showed that an increase in dietary Thr resulted in an increase and then a decrease in daily weight gain in both periods. Peak daily weight gain responses appeared in geese fed the 0.74%Thr diet in both periods (36.120 and 61.96 g, respectively). Thr supplementation significantly affected feed/gain in the 0–4 week period (P ≤ 0.045) and daily feed intake in the 5–8 week period (P ≤ 0.012). No significant linear or quadratic responses from Thr supplementation were observed in growth performance and carcass traits of geese except for eviscerated carcass percentage (quadratic effect, P ≤ 0.016). The optimal Thr requirement of Yangzhou geese from 0 to 8 weeks of age was 0.726% for eviscerated carcass percentage. The results of our experiment reported herein would document that the Thr requirements suggested by NRC (1994) for geese up to 8 weeks of age are safe estimates; they may slightly overestimate the requirements but not by a large margin.