Application Of Phytosterols And Tannic Acid In The Diet Of Largemouth Bass (Micropterus Salmoides)

Largemouth bass(Micropterus salmoides),as a typical carnivorous fish,is intolerant to high levels of carbohydrate in its diet.Therefore,in order to alleviate or improve the negative effects of high carbohydrate diets on largemouth bass,this study focused on the effects of phytosterols and tannic acid on growth performance,body composition,antioxidant capacity,muscle texture,liver and intestinal health of largemouth bass,with a view to providing a reference basis for the application of phytosterols and tannic acid in largemouth bass diets.1.Effects of dietary phytosterols levels on growth performance,muscle texture,liver and intestinal health of juvenile Largemouth bass(Micropterus salmoides)An 8-week feeding trail was carried out to investigate the effects of dietary phytosterol content on the growth performance,muscle texture,liver and intestinal health status and of largemouth bass(Micropterus salmoides).Phytosterol was supplemented into a basal diet with the levels of 0(TZ0),22.70(TZ22),45.00(TZ45),67.50(TZ67)and 90.00(TZ90)mg/kg,and 600 largemouth bass(initial average weight 5.01 ± 0.06 g)were randomly divided into 5 groups,with 3 replicates in each group,and 40 experimental fish in each replicate.Five diets were fed according to the grouping design of the experiment.The results showed as follows: compared with TZ0 group,the diets supplemented with phytosterol had no significant effect on the growth performance and feed utilization of the experimental fish(P > 0.05);the crude fat content of whole fish,glycogen content of liver and muscle decreased significantly(P < 0.05),while the water content of whole fish and muscle increased significantly(P < 0.05);The activities of ALT and AST in serum of experimental fish in TZ22 and TZ67 groups decreased significantly(P < 0.05),blood glucose in TZ45 and TZ90 groups increased significantly(P < 0.05),and triglyceride levels in TZ22,TZ67 and TZ90 groups increased significantly(P < 0.05);Serum catalase(CAT)activity increased significantly in TZ45 and TZ67 groups(P < 0.05),while serum malondialdehyde level and liver CAT activity decreased significantly in TZ90 group(P < 0.05);the hardness,stringiness and adhesiveness of the muscle of the experimental fish were significantly improved(P < 0.05);The diets supplemented with phytosterol had no obvious effect on the liver structure of experimental fish,the width of hepatocytes in TZ90 group was significantly increased(P < 0.05),and the a* value of liver in TZ45 group was significantly increased(P < 0.05);there was no significant change in the characteristics of intestinal villi(P > 0.05).Through intestinal slices,it can be found that the intestines of test fish in TZ0 group are obviously damaged,while the intestinal villi in TZ 22,TZ 45,TZ 67 and TZ 90 groups are complete,and the abnormal phenomenon of intestinal villi is not obvious.It is concluded that the diet supplemented with an appropriate amount of phytosterol can significantly improve its liver,intestinal health and muscle physical quality(P < 0.05).Through the quadratic regression model to analyze its whole fish crude fat and liver glycogen,it can be concluded that the optimal addition level of phytosterol in the feed of largemouth bass is 59.2 ~ 64.0 mg/kg.2.Effects of tannic acid supplementation on growth,antioxidant capacity,digestive enzyme activity,liver and intestinal histology of juvenile Largemouth bass(Micropterus salmoides)An 8-week feeding trial was conducted to investigate the effect of dietary tannic acid(TA)on growth performance and health status of juvenile largemouth bass,Micropterus salmoides(initial mean weight: 5.01 ± 0.06 g).Five isonitrogenous and isolipidic experimental diets were designed,which were LC0(carbohydrate level was 16%),HC0(carbohydrate level was 21%),HC200(carbohydrate level was 21% + 200 mg/kg TA),HC400(carbohydrate level was 21% + 400 mg/kg TA)and HC800(carbohydrate level was 21% + 800 mg/kg TA),with 3 replicates in each group,and 20 experimental fish in each replicate.Results showed that among fish fed the high carbohydrate diets,dietary TA level had no significant effect(P > 0.05)on the growth performance and feed utilization.However,compared to fish fed LC0 diet,fish fed HC400 and HC800 diets had higher survival rate,but lower the final weight,weight gain and specific growth rate(P < 0.05).The liver glycogen level was lower,when the fish fed diets supplementation of TA in 400~800 mg/kg diet than the HC0 diet(P < 0.05).Serum and liver catalase(CAT)activities of fish fed HC200 diet were significantly higher than the fish fed HC0 diet(P < 0.05).However,serum CAT activity was also significantly increased in fish fed 400 mg/kg TA diet(P < 0.05),and the serum malondialdehyde(MDA)content was significantly decreased(P < 0.05).Compared with fish fed HC0 diet,the liver protease activity was higher(P < 0.05),while the protease activity in pyloric caecum and intestine were lower(P < 0.05)when the fish fed 200~800 mg/kg TA diets.Intestinal epithelial cell vacuolation and necrosis were reduced in fish fed TA supplemented diets compared to fish fed LC0 and HC0 diets.In conclusion,dietary supplementation of 200 ~ 400 mg/kg tannic acid had no negative effects on growth performance,feed utilization and survival rate of largemouth bass,improved liver and intestinal health,and increased antioxidant capacity.In summary,phytosterols and tannic acid as dietary supplements have a certain improvement effect on the antioxidant capacity,liver and intestinal health of largemouth bass.