Effects of Selenium-Enriched Probiotics on Growth and Antioxidant Level of Juvenile Tilapia( Oreochromis niloticus)

This experiment was conducted to study the effects of selenium-enriched probiotics on growth and antioxidant level of juvenile tilapia( Oreochromis niloticus). Six hundred juvenile tilapia with an average initial body weight of( 12.40±0.13) g were randomly chosen and distributed into 5 groups with 3 replicates in each group and 40 fish in each replicate. The fish in control group were fed a basal diet containing 0.257 mg / kg selenium,and the fish in other four groups were fed experimental diets supplemented with selenium-enriched probiotics. The selenium-enriched probiotics were composed by selenium-enriched yeast,yeast and lactic acid bacteria with different proportions. The supplemental levels of selenium-enriched yeast converted into selenium supplemental levels were 0( group A),0.4( group B),0.6( group C) and 0.8 mg / kg( group D),respectively,while the supplemental levels of lactic acid bacteria were all 3. 04 × 105CFU / g,and the supplemental levels of living bacteria were the same by adjusting yeast supplemental level in the 4 experimental diets. The experiment lasted for 70 days. The results showed as follows: the highest of special growth rate in the stages of days 50 to 60 and days 60 to 70 was found in groups D and C,respectively,and was significantly higher than that in control group( P0.05). The activity of serum glutathione peroxidase( GPx) on day 30 and day 50 in group C was significantly higher than that in group A( P0.05),and the activity of serum GPx on day 60 in control group was significantly lower than that in other groups( P0.05). On day 30,groups C and A had the highest and the lowest serum catalase( CAT) activity,respectively,and there was significant difference in serum CAT activity among all groups( P0.05). The activity of serum CAT on day 60 in control group was significantly lower than that in groups A,B and C( P 0. 05). The activity of serum superoxide dismutase( SOD) on day 30 and day 50 in group C was significantly higher than that in other groups( P0.05). The relative expression level of liver glutathione peroxidase 1( G Px1) mRNA in each group was firstly increased with feeding time extending; subsequently,it was decreased after reached the highest value on day 50. The relative expression level of liver G Px1 mRNA in groups A and C was significantly higher than that in other groups( P 0.05),and group C had the highest value. In conclusion,the supplementation of 0.6 mg / kg selenium-enriched probiotics( counted with selenium) in the basal diet with 0.257 mg / kg selenium can improve the growth and antioxidant level of juvenile tilapia with the body weight of 12 to 55 g per fish.