| Three experiments were conducted in our study to evaluate the effects of dietary vitamin K3supplemental levels on clotting time,tibial bone quality,vitamin K-dependent proteins and cecum flora of Pekin ducks,We aimed to screen sensitive indicators reflecting the nutritional status of vitamin K in meat ducks,to determine the vitamin K requirements of Pekin ducks,to explore the regulation mechanism of vitamin K on bone formation by measuring the marker gene expression of tibial osteoblasts,We further explored the effects of dietary supplementation of vitamin K3 on the cecal microbial diversity and the correlation between cecal bacteria and tibia growth,to provide theoretical basis for the use of vitamin K3 in meat duck and the nutritional regulation mechanism of vitamin K to promote tibia growth.The experiment 1 was conducted to investigate the effects of vitamin K3 sources and supplemental levels on tibia growth in Pekin ducks.using corn-soybean meal-soybean protein isolate diet as the basic diet.There are 13 diet treatment groups with two vitamin K3 sources.Among them,menadione sodium bisulfite（MSB）and menadione bisulfite（MNB）are two sources of vitamin K3.The 13 diet treatment groups include 1 control group fed with basal diet,6 MSB addition groups,6 MNB addition groups.with 6 vitamin K3 supplemental levels（0.5,1.0,2.0,4.0,6.0,8.0 mg/kg）.A total of 832 one-day-old male Pekin ducks were randomly divided into 13 groups with 8 replicates each group and 8 birds per replicate.the experiment lasted for 21 days.The results showed as follows:There was no significant difference between all groups on the growth performance and carcass traits of 21-day-old Pekin ducks（P>0.05）;When the vitamin K3 supplemental level was 2.0 mg/kg,tibia quality indicators such as tibia length,defatted weight,ash weight,and bone density were significantly improved（P<0.05）;The content of plasma calcium of the control group was significantly lower than those of the 4 mg/kg MSB and 0.5 mg/kg MNB supplemental level groups（P<0.05）.The content of plasma phosphorus of the control group was significantly lower than those of the 2.0,4.0,6.0,8.0 mg/kg MSB and 0.5,4.0,8.0mg/kg MNB supplemental level groups（P<0.05）,and there was no significant difference in the effects of two vitamin K3 sources on tibia quality and bone metabolism indexes（P>0.05）.The content of plasma PIVKA-Ⅱof the 8.0 mg/kg vitamin K3supplemental level groups was significantly lower than the control group（P<0.05）.The content of plasma uc OC of the vitamin K3 supplement groups were significantly lower than the control group（P<0.05）.When the vitamin K3 supplemental level was 2.0mg/kg,the expression of tibial osteoblast marker gene STC2 and vitamin K-dependent protein carboxylase marker gene GGCX were significantly up-regulated（P<0.05）,which promoted osteoblast differentiation.The experiment 2 was conducted to investigate the effects of supplemental levels vitamin K3 with corn-soybean protein isolate diets on blood coagulation and tibia growth in Pekin ducks.There are 6vitamin K3 supplemental levels（0.0,0.5,1.0,2.0,3.0,4.0 mg/kg）,and MSB was vitamin K3 source.A total of 180 one-day-old male Pekin ducks were randomly divided into 6 groups with 5 replicates each group and 6 birds per replicate.the experiment lasted for 21 days.The results showed as follows:There was no significant difference between all groups on the growth performance,carcass traits,bone mineral density and bone strength of 21-day-old Pekin ducks（P>0.05）.But the bone flexibility of the control group was significantly lower than those of the 1.0,2.0 mg/kg vitamin K3supplemental level groups（P<0.05）,The cartilage thickness of the control group was significantly lower than 8.0 mg/kg vitamin K3supplemental level groups（P<0.05）,The content of serum phosphorus of the control group was significantly lower than those of the 1.0,2.0,3.0,4.0 mg/kg vitamin K3supplemental level groups（P<0.05）.Different vitamin K3 supplemental levels had significant effect on the prothrombin time of14-day-old Pekin ducks（P<0.05）,according to prothrombin time,the evaluation of vitamin K3requirements of Pekin ducks were 2.00 mg/kg by broken-line regression models.The content of serum PIVKA-Ⅱand uc OC of the control group was significantly higher than vitamin K3supplement groups of 21-day-old Pekin ducks（P<0.05）,and the content of serum uc MGP of the control group was significantly lower than those of the 1.0,2.0,3.0,4.0 mg/kg vitamin K3supplemental level groups（P<0.05）.The expression of tibial osteoblast marker gene STC2 and OPG of the vitamin K3 supplement groups were significantly up-regulated compared with the control group（P<0.05）.The experiment 3 was based on experiment 2 to investigate the effects of dietary supplementation of vitamin K3 on the cecal microbial diversity of Pekin ducks.6 ducks were selected from the control group and 2.0 mg/kg vitamin K3 supplementation groups.The cecal microbial diversity of the two groups was measured,and the correlation analysis between the flora and tibia growth was performed on genus level.The results showed as follows:Dietary supplementation of vitamin K3 could significantly increase the Bacteroides（P<0.05）;In the vitamin K3 group,Weissella,Prevotella,Staphylococcus,and Lactobacillus were the dominant bacteria genera compared to the control group;Lefse shows that Firmicutes、Bacteroides can be used as a biomarker for the control group and vitamin K3 group;There was significant positive correlation between Bacteroides and tibia growth indicators（P<0.05）.In conclusion,dietary supplementation of vitamin K3 could improve the blood coagulation and tibial quality of Pekin ducks.Vitamin K had effects on vitamin K-dependent proteins such as PIVKA-Ⅱ,osteocalcin,matrix Gla protein by participating in carboxylation,and affects the body’s coagulation function and bone growth.In addition,vitamin K could up-regulate the expression of STC2 and OPG in osteoblasts,which promoted osteoblast differentiation.According to prothrombin time of 14-day-old Pekin ducks,the evaluation of vitamin K3 requirements of Pekin ducks were 2.00 mg/kg.Dietary supplementation of vitamin K3could increase Bacteroides in cecum,which was significantly positively correlated with tibia growth. |
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