The influence of the amylopectin/amylose ratio in samples of corn on the true metabolizable energy value for ducks

The present study was conducted to investigate the relationship between amylopectin (AP), amylose (AM) content and AP/AM ratio of corns and true metabolizable energy (TME) value for ducks, and further to establish the prediction equations to estimate the TME value of corns. Six representative samples were selected from 21 corn samples based on the AP/AM ratio. According to the modified Sibbald's method, male Cherry Valley ducks were then used to assay the TME values. Stepwise regression analysis was performed to establish the prediction equations of TME values using dry matter (DM), crude protein (CP), ether extract (EE), ash, crude fiber (CF), acid detergent fiber (ADF), neutral detergent fiber (NDF), AM, AP, AP/AM and gross energy (GE) as independent variables. Correlation analysis exhibited a significant positive correlation of AP (r = 0.84, P<0.05) and AP/AM (r = 0.86, P<0.05) contents with the TME value of corns for ducks. The regressive equation for predicting TME with AP/AM ratio was established as TME = 1.9463AP/AM + 10.31246 (r2 = 0.7674, P<0.05). With the introduction of ash and NDF, the more optimal equation: TME = 1.7624AP/AM − 0.0487AM + 0.7984ash + 0.1655NDF + 8.4880 (r2 = 1.0000, P<0.01) was obtained. These results indicate that the AP/AM ratio in corns was one of the major factors that affect the TME value for ducks and could be used as an important index for evaluating corn bioavailable energy.