| Three methods, amino acid (AA) deletion method, analysis of whole body AA accretion (feather and carcass separately ),and total needs of maintenance plus accretion, were used in the present study to investigate the ideal pattern of the following essential amino acids (EAA): lysine (Lys), methionine (Met), threonine (Thr), tryptophan (Trp),argnine (Arg),vaiine (Vai), and isoleucine (lie), which are usually the limiting AAs in the diet of meat-type duck. during the early growth stage(O-3W) The study was carried out in four relative experiments: Exp. 1, AA deletion growth assay and comparative slaughter experiment; Exp.2, Feedstuffs?AA digestibility determination with adult drake by Sibbald's force-feeding method, meanwhile ,using nitrogen free diet (NFD) to measure the endogenous amino acid loss (EAAL); Exp.3, Feedstuffs?AA digestibility determination with two-week-old duckling fed ad Iibitum, with same EAAL measurement method of exp.2, while the feather and skin shedding of the 4 NFD groups were gathered; Exp.4, EAAL, feather and skin shedding determination with two-week-old duckling by Difference Method. Exp. 1: Single Factor design was adopted. 12 diets based on corn-soybean meal and estimated DAA contents were formulated and fed randomly ad Iibitum to 192 three-day-old Tianfu meat ducks for 15 days with 4 replicates of one diet. The 12 diets were formulated on the following principles: conventional control (C) only added Lys and Met to meet the 100% needs of all AA with crude protein (CP) level 17.08%, high protein control (HC) added 6 synthetic amino acids (SAA) to meet 100% needs of all AA with CP 15.67%, low protein control (LC) only meet 80% need of all AAs with CP 14.50%, LC plus SAA (LC) to meet 100% need of all AA with CP 14.92%, Lys, Met, Thr, Tip, Val and lie diets were those that only 20% of the corresponding tested AA were deleted from LC diet. Another diet, Glu, which was formulated 4 only delete the added L-GIu from LC4, because in which L-Glu was added according to the 55% difference of CP between LC and HC to guarantee the adequate supply of non-essential amino acids (NEAA).Therefore, the intact protein in each diet, except C and HC, was same. At the end of growth essay, 2 birds with average body weight of the replicate were killed with no blood shedding. CP accretion of all killed birds were analyzed for carcass and feather separately. AA accretion was analyzed with fat-extracted carcass mice and feather samples only for 8 groups with representative final body weight, because the AAPS of different sample (the lightest and the weightiest groups) were almost the same. Exp.2: Sixteen adult drakes with similar body weight were used in 3 turns to determine the TAAD of corn and soybean meal with 4 replicates (4 birds) of each diet (Corn diet~ soybean meal diet and NFD). Exp.3: Forty-eight two-week-old Tianfu ducklings were divided into 12 groups to determine the TAAD of corn and soybean meal with 4 replicates (4 birds) of one diet (same as exp.2). Feather and skin shedding of the groups fed NFD were gathered carefully. Exp.4: The assay was carried out in same as exp.3, but the 3 diets were different. Keeping constant ratio of corn and soybean meal, the CP of dietl (Dl), diet 2 (D2) and, diet 3 (D3) were 17.50, 15.00, and 12.50% respectively by adding corn starch to dilute CP concentration. According to Difference Method, the TAAD and EAAL were calculated. The feather and skin shedding of each group were also carefully gath...
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