| The experiment was conducted to study the effects of different levels of selenium(sodium selenite) on growth performance and biochemical indexes in growing laying ducks(5～11weeks). One hundred and fifty Jing ding ducks with an average body weight of (0.36±0.01) kg were chosen and randomly divided into5groups with6replicates of5ducks in each replicate. The ducks were fed basal diet (the selenium content was0.04mg/kg) supplemented0,0.08,0.16,0.36and0.66mg/kg Se(actual additives as sodium selenite), respectively. The trial lasted for7weeks. In the experiment, the ducks weight and surplus feed were weighted every two weeks to calculate daily gain, daily intake feed and feed gain ratio. At the end of the feeding trial,6ducks with weight close were randomly selected in each treatment to collect fasting blood and slaughter, and then to take out the liver and immune organs including liver, spleen, bursa and thymus.The results of growth performance showed that the effect of different levels of selenium had no significant influence on feed intake (P>0.05), daily gain and feed conversion ratio was significantly influenced (P<0.05), supplementation of0.08and0.16mg/kg Se in diet significantly improved average daily gain, and reduced the ratio of feed to gain.The results of antioxidant indicators showed that Se levels in diet had very significantly increased the activities of GSH-Px (P<0.01),and had significantly increased the activities of T-AOC and CAT in serum(P<0.05), adding0.16mg/kg Se the activity of GSH-Px、T-AOC and CAT was the most highest. but the activities of SOD and MDA concentration were not influenced by different levels of Se (P>0.05).The activities of GSH-Px、SOD、CAT'MDA concentration with supplement of0.16mg/kg Se was much higher than those in the control group in liver(P<0.05), but the activities of T-AOC were not influenced (P>0.05).With Se levels increasing, the activity of GSH-Px, T-AOC,SOD and CAT was firstly increased and subsequently decreased, but MDA had the opposite tendency.The results of immune test showed that addition of0.08mg/kg Se in diet had significantly higher the weight of spleen and bursal and bursal indices than those control gropes (P<0.05), the ALB and GLB were increased significantly by adding of0.08mg/kg Se than those adding of0.66mg/kg Se (P<0.05), and there were significant differences in the IL-2and coneentrations of serum immunoglobul(IgA、IgM、IgG) when the addition level was0.08,0.16mg/kg (P<0.05),but indices of spleen and thymus, thymus weight,TP and A/G were not influenced by different levels of Se (P>0.05). The results of hormone in serum test showed that the content of T3and INS first increased and then decreased as the level of Se increased, while the content of T4first decreased and then increased as the level of Se increased, but all groups were not influenced (P>0.05), the GH content and T3/T4in addition of0.16mg/kg Se group was much higher than those in the control group and the0.66mg/kg Se group (P<0.05).The results of physological and biochemical in serum test showed that the concentration of GLU,BUN,TG,TC,LDH and ALP was reduced by adding different Se level (P>0.05).According to the growth performance, organism antioxidant, immunity, serum biochemical indexes, addition of0.08mg/kg in the corn-soybean meal diets(he selenium content was0.04mg/kg) which can satisfy the growth needs, suitably increaseing selenium comtent can enhance antioxidant, immunity and other biochemical indexes.It is suggested that the optimal supplement amount of selenium was from0.08mg/kg to0.12mg/kg under cage condition at the stage of young laying ducks, that selenium content was0.12mg/kg to0.20mg/kg in the diet... |
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