| In recent years,many scholars have tried to use Chinese herbal medicine as feed additives to improve the health of animal.So far,enzymatically treated Artemisia annua L.(EA)has been effective in livestock and poultry animals,but it has not been used in aquaculture.This study was conducted to investigate the effects of EA on growth performance,serum biochemical index,antioxidant ability,intestinal and liver histology,intestinal microbiota and glucose and lipid metabolism of largemouth bass(Micropterus salmoides),providing guidance and basic data for the application in aquaculture.Experiment 1: Effects of EA on growth performance,serum biochemical index,antioxidant capacity,liver and intestinal health largemouth bass.A total of fish,with average initial body weight(14.75±0.50 g),were randomly divided into six groups with three replicates of 40 fish in each replicate and fed with diets with the recruitment of 0g/kg(EA0),0.25g/kg(EA0.25),0.5 g/kg(EA0.5),1 g/kg(EA1),2 g/kg(EA2)and 4g/kg(EA4),respectively.Experiments were performed for 8 weeks.The results were as follows: 1)As dietary EA level increased,the feed conversion ratio(FCR),survival rate(SR),protein efficiency(PER),feed intake rate(FIR)and viscera somatic index(VSI)among all treatments had no significant differences(P > 0.05).Final body weight(FBW),weight gain(WGR)and specific growth rates(SGR)increased first and then decreased(P < 0.05),and were significantly higher than that of the control group when dietary EA ranged from 0.25 g/kg to 1 g/kg(P < 0.05);The addition of EA have no significant difference between the treatment groups(P > 0.05);The condition factor increased first and then decreased(P < 0.05),and was significantly higher than that of the control group in EA0.25 and EA0.5 group(P < 0.05);There was no significant effect on the hepatic somatic index(HSI)when the level of EA was lower than 1 g/kg(P > 0.05),and the HSI was significantly reduced as the level of EA was further increased(P < 0.05).Dietary EA level had no significant effects on moisture,crude protein,crude lipid and ash of largemouth bass(P > 0.05).2)Dietary EA level had no significant effect on the content of albumin(ALB)and alanine transaminase(ALT)in serum(P > 0.05).The content of total protein(TP)increased first and then decreased(P< 0.05),and reached the highest level in EA2 group.The content of total cholesterol(TC)and triglyceride(TG)in serum decreased first and then increased(P < 0.05),and were the lowest level in EA0.5 group.The content of glucose(GLU)in serum decreased first and then increased(P < 0.05),and reached the lowest level in EA2 group.High-density lipoprotein and low-density lipoprotein in serum showed completely opposite trends,reaching the highest and lowest levels in the EA0.5 group,respectively(P < 0.05).Aspartate transaminase(AST)activity in serum increased first and then decreased,and were significantly lower in treated groups when compared to the control group(P < 0.05).3)Dietary EA level had significant effect on the total antioxidant capacity(T-AOC)in serum,liver and intestine(P < 0.05).With the increase of EA,all above indexes increased first and then decreased,and reached the highest level in EA0.5group(P < 0.05);Both catalase(CAT)in serum and superoxide dismutase(SOD)and CAT activity in liver and intestine increased and decreased,reaching the highest level in EA0.5 group(P < 0.05)while serum SOD activity was unaffected by EA(P > 0.05).Malonaldehyde(MDA)and protein carbonyl(PC)in serum and liver showed a completely opposite trend to the above indicators(P < 0.05).MDA in intestine was not changed significantly(P > 0.05),the content of PC in intestine decreased first and then increased,reaching the lowest level in EA1 group(P < 0.05).In EA0.5 group,the m RNA expression of hepatic Nrf2,Cu Zn SOD,and CAT was significantly higher than that in the control group(P < 0.05).The m RNA expression of hepatic Keap1 was significantly lower than the control group(P < 0.05),but had no significant effect on the m RNA expression of hepatic HO-1 and GPx(P > 0.05).No significant effect on the m RNA expression of these above genes in intestine(P > 0.05);In EA4 group,the m RNA expression of hepatic Nrf2,Cu Zn SOD,HO-1 and GPx was significantly higher than that in the control group(P < 0.05).The m RNA expression of hepatic Keap1 was significantly lower than that the control group(P < 0.05),but had no significant effect on the m RNA expression of hepatic CAT(P > 0.05).The m RNA expression of Nrf2,CAT,HO-1 and GPx was significantly increased in intestine,and no significant effect on the m RNA expression of Keap1 and Cu Zn SOD in intestine(P > 0.05).4)When the level of EA was 0.25～1 g/kg,the hepatocytes had clear boundaries,uniform size,close arrangement,and the vacuolization of hepatocytes was relieved.Meanwhile,the intestinal morphology indicators all showed an upward trend and reached the highest value of 1 g/kg(P < 0.05).5)In EA0.5 group,the diversity of intestinal microbiota were significantly reduced(P < 0.05)and affected the composition intestinal microbiota of largemouth bass(P > 0.05).Above all,EA can improve the growth performance,enhance the antioxidant capacity and the liver and intestinal health of largemouth bass.According to the above experimental results,the optimal dietary EA of largemouth bass was 0.33g/kg.Experiment 2: Effect of EA on glucose and lipid metabolism in largemouth bass.The effects of EA on the transcriptional level of lipid synthesis,lipid oxidation,glycolysis and gluconeogenesis and transcription factors of largemouth bass were analyzed in this study.The results are as follows: 1)In EA0.5 group,the addition of EA significantly increased the m RNA expression of CPT-1(P < 0.05),and had no significant effect on the m RNA expression of other genes related to lipid metabolism(P > 0.05);In EA4 group,the addition of EA significantly increased the m RNA expression of SREBP1-c,ACCα,FASN,HMGCR,PPAR and ACCβ(P < 0.05),and reduced the m RNA expression of CPT-1(P < 0.05).2)In EA0.5 group,the addition of EA significantly increased the m RNA expression of Fox O1 and PFK(P < 0.05),and had no significant effect on the expression of other glucose metabolism-related genes(P > 0.05);In EA4 group,the m RNA expression of Fox O1,PEPCK,FBP,GK and PK were significantly higher than control group(P > 0.05),and CREB and G6 P were not significantly different from control group(P > 0.05).The above results show that Suitable dose EA can promote lipid metabolism and glucose metabolism in largemouth bass. |
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