The Effects Of Selenium On Growth,Antioxidant Ability And Nitrite Stress Resistance For Pacific White Shrimp (Litopenaeus Vannamei)

A feeding trial was conducted to determine the effects of Hydroxyl-methionine Selenium on growth,antioxidant ability,nitrite stress resistance for Litopenaeus vannamei.Two levels of fish meal diets were set up,including 30% and 15% of fish meal respectively.Five different selenium levels was added to the two basic diets,and the levels of selenium added was 0.0,0.15,0.30,0.60 and 0.90 mg/kg.Ten practical diets were formulated.the results showed that:1.Effects of dietary hydroxy-methionine selenium levels on growth performance,body composition,serum biochemical indexes and antioxidant ability of Litopenaeus vannameiIn the 30% fish meal groups,MBW,WG,SGR and FER reached a maximum in 0.30 mg/kg selenium group and were significantly higher than that in 0.90 mg/kg selenium groups,but no significant differences with the other groups(P>0.05).In the 15% fish meal groups,MBW,WG,SGR,FER and PER reached a maximum in 0.30 mg/kg selenium group and were significantly higher than that in 0.60 and 0.90 mg/kg selenium groups.Two-factor analysis showed that MBW,WG,SGR,FER,FI,PER and SR were significantly affected by fish meal and selenium levels(P<0.05),but were not affected by the interaction between selenium level and fish meal level(P>0.05).In the 30% and 15% fish meal groups,Two-factor analysis showed that crude fat was significantly affected by selenium levels and interaction(P<0.05).The selenium content in whole shrimp and muscle increased with the addition of selenium in feed and reached a difference among groups(P<0.05).In the 30% and 15% fish meal groups,The results of double factor analysis showed that TG,CHO,ALT and AST were significantly affected by selenium level and fish meal level(P<0.05),which were also affected by interaction of fish meal and selenium levels(P<0.05).In the 30%fish meal groups,the addition of 0.15 mg/kg selenium into the diet significantly increased the activities of GSH-Px,T-AOC and T-SOD in serum(P<0.05).The activities of GSH-Px and T-AOC were significantly higher than that in the other groups(P<0.05).The activity of GSH-Px,T-SOD,GST and CAT of hepatopancreas in 0.30 or 0.6 mg/kg selenium groups were significantly higher than that in the other groups(P<0.05).The expression of GSH-Px and C-MnSOD mRNA in 0.15 mg /kg selenium group and the expression of CAT and LZM m RNAin 0.60 mg/kg selenium group reached the highest,which were higher than that in the other groups(P<0.05).In the 15% fish meal groups,GSH-Px and T-SOD activities in serum,CAT activity in hepatopancreas,and GSH-Px mRNA expression were the highest in 0.90 mg/kg selenium groups.The activities of GST and T-SOD in hepatopancreas was significantly decreased by adding 0.90 mg/kg selenium(P<0.05).The LZM mRNA expression was the highest in 0.60 mg/kg selenium group,which were higher than that in the other groups(P<0.05).The results of two-factor analysis showed that the selenium level and fish meal level in the feed significantly affected the antioxidant capacity of shrimp and were significantly affected by the interaction between fish meal and selenium levels.2.Effects of dietary hydroxy-methionine selenium levels on the survival rate,biochemical indexes and antioxidant capacity of Litopenaeus vannamei under nitrite stressThe survival rate of shrimp under nitrite stress in the 30% fish meal and 15% fish meal groups were the highest in 0.30 mg/kg selenium group,which was significantly higher than that in the control group(P<0.05),but there was no significant difference compared with the other groups(P>0.05).In the 30% and 15% fish meal groups,The results of double factor analysis showed that GLU,TG,CHO,ALT and AST were significantly affected by selenium level and fish meal level(P<0.05).In the 30% and 15% fish meal groups,The activities of GSH-Px,T-SOD and ALP in serum and the activities of GST,T-SOD and CAT in hepatopancreas were lower than those before the stress,but the activity of GSH-Px in serum and the content of MDA in hepatopancreas were higher than those before stress.In general,the addition 0.30 mg/kg of hydroxy-methionine selenium in the 30% fish meal and 15% fish meal groups can improve the growth performance and feed utilization,and the addition of hydroxy-methionine selenium can inprove the ability of antioxidant capacity and resistance to nitrite stress of Litopenaeus vannamei.But which is influenced by the level of fish meal,selenium level and the interaction between them.