| This experiment was conducted to investigate the effects of dietary vitamin E level on growth performance and biochemical indices of egg-type ducklings aged1to28days, and to estimate the optimal dietary vitamin E level by NLIN. A total of180one-day-old healthy Jinding egg-type ducklings with the similar body weight were randomly assigned to5groups with6replicates per group and6ducklings per replicate. The ducklings in the group I (control diet) were fed basal diet (corn-soybean meal-based diet), and those in group Ⅱ to Ⅴ were fed the basal diet supplemented with10,15,20and40IU/kg vitamin E, respectively. The experiment lasted for4weeks.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 to calculate average daily gain and feed intake, and the ratio of feed to gain. At the end of the feeding trial,6ducks which weight closely in each replicate were randomly chosen and collect blood through jugular artery puncture, and killed to take out the liver and immune organs including spleen, bursa and thymus.(1) The results of growth showed that:diets supplemented with VE ducklings feed conversion ratio, average daily gain,average daily feed was significantly affected (P<0.05). With the VE content in the diet increase, average daily gain and feed to gain ratio showed a significant quadratic change trends. Estimate appropriate level of VE is17.6-19.9IU/kg as the optimal amount.(2) The results of antioxidant indices showed that: the appropriate level of VE can significantly improve Laying Ducklings serum and liver T-AOC, T-SOD, serum and liver GSH-Px activity (P<0.05) with increasing the content of dietary VE reduce the significant quadratic trend; showed the first increase with the increase in dietary VE content, can significantly reduce the activity of MDA in the liver (P<0.05), add the estimate of VE appropriate level to take18.6～19.9IU/kg for the best. However, serum MDA and control group were no significant differences (P>0.05).(3) Serum hormone results show that: VE on the Laying Ducklings Thyroid iodine of the original acid (T3), thyroxine (T4) and GH affect significantly (P<0.05) but no significant impact on serum cortisol concentrations (P>0.05).Diet supplemented with15IU/kg vitamin E serum GH was significantly higher than those without added vitamin E group (P<0.05), serum cortisol concentration and the level of vitamin E was negatively correlated, add15IU/kg of vitamin E on serum T3, T4increased the more obvious differences between groups were significantly (P<0.05). From thyroxine (T4) of GH estimated VE appropriate to add the amount to take17.0～19.5IU/kg as the optimal. (4) The results of serum immune indices showed:serum immunoglobulins (IgA, IgM, IgG), white interleukin-2with the increase in dietary vitamin E levels tended to increase, add15IU/kg VE group IgA, IgM, interleukinThe difference between-2each significantly (P<0.05); of IgG index differences between groups was not significant (P>0.05); estimate the the VE appropriate amount to take from the IgA, IgM, and interleukin-218.4-18.9IU/kg is the best dosage. The results of immune organ indices showed that dietary supplementation of15IU/kg VE thymus, bursal index than the control group significantly increased (P<0.05), but the spleen of each group difference was not significant (P>0.05).These results combined with considering production performance, immunity, hormones related to metabolism and antioxidant functions indicated that basal diet supplemented with moderate level of vitamin E can improve growth performance, immunity, and antioxidant functions of egg-type ducklings. Based on the various indicators, the optimal vitamin E supplemental levels estimated by quadratic regression model analysis are17.0to19.9IU/kg. |
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