Abstract: The goal of this experiment was to determine the apparent metabolizable energy (AME) and true metabolizable energy (TME) of chicken from various corn and sorghum sources using the free feeding method (FF) and tube feeding method (TF), and to compare the effects of the two evaluation methods on chicken available energy. The experiment was conducted in 3 phases. A total of 108 healthy mature Hyland brown shell roosters were chosen, with 96 roosters divided into FF and TF groups based on the principle of uniform body weight. Each method consisted of 12 dietary treatments, with four chickens treated with one diet, with a replicate of two chickens designed in the FF method group and a replicate of one chicken designed in the TF method group. The 12 dietary treatments included 6 sources of corn diet, corn-soybean meal basal diet, and 5 sources of sorghum diet. All excreta were collected to determine the AME and TME of diets and ingredients. Another 5 roosters weighing similar to the test group were selected to determine the endogenous loss. The results were showed as follows:1) The AME values range of 6 kinds of corn determinated by the FF method was 15.82~16.23 MJ·kg^-1 DM (P<0.05, CV=0.98%), and the TME values range was 15.95~16.36 MJ·kg^-1 DM (P<0.05, CV=0.99%). The AME values of 5 sorghums ranged from 13.43~15.37 MJ·kg^-1 DM (P<0.05, CV=5.16%), and the TME values ranged from 13.59~15.48 MJ·kg^-1 DM (P<0.05, CV=5.10%). 2) The AME values range of 6 kinds of corn assessed by the TF method was 14.35~15.01 MJ·kg^-1 DM (P<0.05, CV=1.66%), The TME values range was 16.00~16.64 MJ·kg^-1 DM (P<0.05, CV=1.45%). The AME values range of 5 sorghums was 12.51~14.87 MJ·kg^-1 DM (P<0.05, CV=6.74%), and the TME values ranged from 14.08 to 16.45 MJ·kg^-1 DM (P<0.05, CV=6.04%). 3) The AME values of the 6 corn measured by the FF method were 9.42% higher than the values measured by the TF method (P<0.05), but there was no significant difference in TME value determinated by FF on TF method. The AME values of the 5 sorghum measured by the FF method were 5.65% higher than the values measured by the TF method (P<0.05), while the TME values determined by the TF method were 4.82% higher than that measured by FF (P<0.05). It can be concluded that there are significant differences in the available energy values of chickens from different sources of corn and sorghum, and methodology will influence the determination of the available energy value of corn and sorghum fed to chickens.

Key words: free feeding method, tube feeding method, corn, sorghum, available energy