Two hundred and fourteen unsexed 1-day old white peckin duck chicks with initial live weight of 54.70±0.04 g, were randomly divided into four experimental groups with three replicate in each, with 20 ducks (4x3x20). They used to study the effects of different supplementation levels of threonine (THR) (0.5, 1 and 1.5% /kg diet) on peckin duck performance, some blood metabolites. White peckin duck were raised for 6 weeks in an open house system and were offered both feed and clean drinking water ad-libitum. During the experimental period, body weight (BW), weight gain (BWG), feed intake (FI) and feed conversion ratio (FCR) were recorded weekly. At the end of the feeding trial, five ducks from each treatment were randomly selected weighed, fasted for 12 hrs prior to slaughter by slitting the jugular vein. Significant differences (P≤0.05) were observed among all treatments during the experimental period, for the pervious parameters. At the end of the experimental period, peckin ducks fed diet supplemented with 1 and 1.5% of Thr /Kg diet had significantly the highest body weight, followed by those received 0.5% of Thr /Kg diet by (9.5, 9.15 and 6.1%), respectively compared with the control group. The same direction was found for body weight gain, Feed conversion ratio was improved by using different levels of Thr. Group fed diet supplemented with 1.5% of Thr in diet had significantly (P≤0.05) the best FCR followed by those received 0.5% of Thr in diet then those treated with 1% of Thr in diet compared with ducks in control groups. Hematological parameters of white peckin ducks affected by threonineare listed in table (3). The results indicated that, no significant differences among all treatments for globulin (g/dl), Cholesterol (mg/dl), HDL (mg/dl), ALT (U/L), AST (U/L) when compared with control one while white peckin ducks which fed diets containing with Thr had a significant effect for total protein and albumin. The microscopic examination for the liver and kidney of the control group and ducks which fed different levels of Thr revealed normal histological structure of the hepatoctic acini