Effects Of Zn-MHA On Growth,Digestion And Antioxidant Capacity Of Procambarus Clarkii

Procambarus clarkii is one of the important economic species of freshwater aquaculture in China.In recent years,with the increase of market demand,the amount of breeding has also gradually increased.The appropriate addition of nutrients in the artificial compound feed can ensure the balanced intake of nutrients in the breeding process of Procambarus clarkii,promote growth,enhance disease resistance,and also reduce pollution of aquaculture water,which is conducive to the rapid development of large-scale aquaculture.As an essential trace element,zinc can promote growth,improve immunity,and affect intestinal function in animals.Both zinc deficiency and excess can adversely affect the animals.However,the optimal amount of zinc in the diet of Procambarus clarkii is stil unclear,which is which is extremely unfavorable to the development of the crayfish aquaculture industry.Zn-MHA is the third-generation zinc product,with a stable structure and a better biological utilization rate.In this paper,Zn-MHA was used as the zinc source,and different levels of Zn-MHA were added to the diet to feed Procambarus clarkii.After the end of breeding,the effects on the growth,digestive capacity,antioxidant,intestinal microbiota composition of crayfish were calculated,determined and analyzed,and the optimal amount was determined,which will lay the foundation for future research and provide theoretical basis.The main study results of this trial are as follows:1.The effect of different concentrations of Zn-MHA on the growth performance of Procambarus clarkii180 Procambarus clarkii juveniles with an average weight of 6.5 g were randomly divided into 5 groups,fed with different Zn-MHA concentration levels(0,15,30,60 and 90 mg/kg)for a period of 8 Weekly feeding trial,5 feed groups designated as X1,X2,X3,X4 and X5 groups.The results show that:(1)Zn-MHA had no significant effect on growth performance indicators such as survival rate(SR),condition factors(CF)and flesh content(FC)(P > 0.05);(2)Zn-MHA had no significant effect on the water and coarse ash content in the muscle of Procambarus clarkii(P > 0.05);(3)Adding 30-90 mg/kg Zn-MHA to the diet can significantly improve the specific growth rate(SGR),weight gain rate(WGR),hepatopancreas index(HSI),crude protein(CP),triglycerides(TG),serum and intestinal zinc content in Procambarus clarkii(P <0.05).(4)The zinc content in the hepatopancreas and muscle had the maximum value in group X5,which was significantly higher than group X1(P < 0.05);(5)Taking SGR and WGR as the judgment standard,the effect was best when 60 mg/kg was added to the feed.The above results indicate that ZnMHA can promote the growth of Procambarus clarkii by participating in the metabolism of nutrients,improving serum biochemical indicators,and increasing the deposition of zinc in tissues.2.The effect of different concentrations of Zn-MHA on the digestive physiology of Procambarus clarkiiIn order to further study the effect of Zn-MHA on the growth performance of Procambarus clarkii,we measured the activities of the hepatopancreas and intestinal digestive enzymes of Procambarus clarkii.The results show that:(1)Adding 30-90mg/kg Zn-MHA to the diet can increase the activity of lipase,amylase and pepsin in the hepatopancreas and intestine of Procambarus clarkii,and the trend is similar to the growth performance.Overall,the enzyme activity was strongest with 60 mg/kg ZnMHA,significantly higher than the control group(P < 0.05);(2)Sequencing analysis of intestinal microbiota,At the phylum level,Proteobacteria,Actinobacteria and Tenericutes were the dominant flora,and at the genus level,the main intestinal microbiota mainly consisted of Rhodobacter,Paracoccus,Pseudomonas,Propionicimonas and Microbacterium;(3)30-90 mg/kg Zn-MHA in diet significantly increased the richness index,30-60 mg/kg Zn-MHA increased the diversity index;(4)Compared with the control group,the abundance of Proteobacteria decreased,and the abundance of Actinobacteria and Tenericutes increased in the experimental group.The above results indicated that the addition of Zn-MHA in the diet could increase the activity of digestive enzymes and promote growth,And increase the richness of the intestinal microbiota of Procambarus clarkii,increase the species diversity,reduce the proportion of harmful bacteria,and promote the colonization of beneficial bacteria.3.The effect of different concentrations of Zn-MHA on the antioxidant and immune ability of Procambarus clarkiiThe enzyme activities and gene expressions related to antioxidant capacity and non-specific immunity in the hepatopancreas of Procambarus clarkii were determined.The results show that:(1)In general,the addition of 15-90 mg/kg Zn-MHA to the diet improved the antioxidant index,immune-related enzymes and the expression of related genes of Procambarus clarkii.(2)In acid phosphatase(ACP),there was no significant difference between the zinc supplemented groups(P > 0.05),but it was significantly higher than the control group(P < 0.05);The addition of 60-90 mg / kg of Zn-MHA in the diet significantly improved the activity of alkaline phosphatase(AKP),prophenoloxidase(PO),and serine protease(SP)in the hepatopancreas(P <0.05),has a maximum value at 60 mg/kg;The 30-90 mg/kg of Zn-MHA increased the expression of the pro PO and CTL genes,Have a maximum value in X5 and X4 groups,respectively,Significantly higher than group X1(P < 0.05);Which reached the maximum at 90 mg/kg and 60 mg/kg,respectively,significantly higher than the control group(P <0.05);(3)Adding 15-90 mg/kg Zn-MHA to the diet significantly increased the activity of catalase(CAT)in the hepatopancreas(P < 0.05),and significantly reduced the content of malondialdehyde(MDA)(P < 0.05),has the lowest value in group X4;Dietary supplementation of 30-90 mg/kg Zn-MHA significantly increased total antioxidant capacity(T-AOC),total superoxide dismutase(T-SOD)and glutathione peroxidase(GSH-PX)(P < 0.05);Meanwhile,the expression level of GPX and Cu Zn-SOD was increased.Generally speaking,the effect was the best when the dosage was 60-90 mg/kg.The above results showed that addind 15-90 mg/kg of Zn-MHA in the basic diet can improve the growth and development of Procambarus clarkii,increase the activity of digestive enzymes,improve the antioxidant and non-specific immunity,At the same time,it also improves the richness of intestinal microbiota and increases species diversity.From the perspective of growth index and digestive enzyme activity,when the dosage was 60 mg/kg,has the best effect.The richness of intestinal microbiota and species diversity were higher at 30-90 mg/kg additions.When the dosage was60-90 mg/kg,the antioxidant capacity of Procambarus clarkii was the strongest.Based on the results of this test,it is recommended to add 60 mg / kg of Zn-MHA to the diet.