Abstract: This experiment was conducted to investigate the effects of vitamin K₃ on coagulation time and vitamin K-dependent proteins of 14-day-old Pekin ducks. In order to screen sensitive indicators reflecting the nutritional status of vitamin K in meat ducks, and determine the vitamin K₃ requirements of Pekin ducks. An one-factor completely randomize design with 6 vitamin K₃ supplemental levels (0, 0.5, 1, 2, 3 and 4 mg·kg^-1) was used in this experiment. The diets were formulated by adding 6 different levels of menadione sodium bisulfite to the corn-soybean isolate basal diets. A total of 180 one-day-old male Pekin ducks were randomly divided into 6 groups with 5 replicates each group and 6 ducks per replicate. The experiment lasted for 14 days. The results showed as follows: Different vitamin K₃supplemental levels had no significant effect on the average daily gain, average daily feed intake and ratio of feed to gain of Pekin ducks from 1 to 14 days of age (P>0.05). The prothrombin time of the 0 and 0.5 mg·kg^-1 vitamin K₃ supplemental level groups were significantly higher than those of 2, 3, and 4 mg·kg^-1 vitamin K₃ supplemental level groups (P<0.05). The level of serum PIVKA-Ⅱ content of the 0 mg·kg^-1 vitamin K₃ supplemental level group was significantly higher than those of the 0.5, 1, 2, 3, 4 mg·kg^-1 vitamin K₃ supplemental level groups (P<0.05); The level of serum undercarboxylated osteocalcin content of the 0 mg·kg^-1 vitamin K₃ supplemental group was significantly higher than those of the 2, 3, 4 mg·kg^-1 vitamin K₃ supplemental level groups (P<0.05). Taking prothrombin time, serum PIVKA-Ⅱ and undercarboxylated osteocalcin as evaluation indicators, vitamin K₃ requirements of Pekin ducks from 1 to 14 days of age was determined as 2.00, 0.56 and 1.27 mg·kg^-1 by broken-line regression models. In conclusion, the supplemental of vitamin K₃ to the diet could enhance coagulation performance, decrease the levels of serum vitamin K-dependent proteins such as the PIVKA-Ⅱ and undercarboxylated osteocalcin. Under the condition of this experiment, according to prothrombin time, the evaluation of vitamin K₃ requirements of Pekin ducks from 1 to 14 days of age was 2.00 mg·kg^-1 by broken-line regression models.

Key words: ducks, vitamin K, coagulation performance, vitamin K-dependent proteins