Effects Of Dietary Vitamin D On Growth Performance And Biochemical Indexes Of Egg-iype Ducklings

This experiment was conducted to investigate the effects of dietary vitamin D level on growthperformance and biochemical indices of egg-type ducklings aged1to28days, and to estimate theoptimal dietary vitamin D level by NLIN. A total of180one-day-old healthy Jinding egg-typeducklings with the similar body weight were randomly assigned to5groups with6replicates pergroup and6ducklings per replicate. The ducklings in the group Ⅰ (control diet) were fed basaldiet (corn-soybean meal-based diet), and those in group Ⅱ to Ⅴ were fed the basal dietsupplemented with110,220,550and1000IU/kg vitamin D, respectively. The experiment lastedfor4weeks.In the experiment, the ducks were weight at the beginning of every week. For each group,ducks weight and surplus feed were record every week.The results of growth showed that supplementation of550IU/kg vitamin D significantlyimproved average daily gain (P<0.05), while reduced ratio of feed to gain (P<0.05), but had nosignificant effect on feed intake (P>0.05).The results of immune organ indices showed that supplementation of550IU/kg of vitamin Dsignificantly increased the thymus and spleen indices (P<0.05), but had no significant effect onbursa indices (P>0.05).The results of serum immune indices showed that supplementation of550IU/kg vitamin Dsignificantly increased the contents of IgG and IgA obviously, while reduced the contents of IL-2and Cort (P<0.05). Supplementation with220or550IU/kg vitamin D both significantly increasedthe contents of TP, ALB, T3and T4in serum (P<0.05).The results of antioxidant indices showed that supplementation of550IU/kg vitamin Dimproved the activities of SOD and GSH-Px in liver (P<0.05), while reduced the contents of MDAin serum and liver (P<0.05). Supplementation of220or550IU/kg vitamin D both significantlyimproved the activities of SOD and GSH-Px in serum and T-AOC (P<0.05) activities in serum andliver.The results of serum enzymes showed that supplementation of220or550IU/kg vitamin Dboth decreased the activities of ALP and LDH in serum (P<0.05).These results combined with considering production performance, immunity, hormones relatedto metabolism and antioxidant functions indicated that basal diet supplemented with moderate levelof vitamin D can improve growth performance, immunity, and antioxidant functions of egg-typeducklings. Based on the various indicators, the optimal vitamin D supplemental levels estimated by quadratic regression model analysis are507.1to560.6IU/kg.