Application Of Tenebrio Molitor Meal In Compound Diet Of Micropterus Salmoides

Due to the shortage of animal protein resources,Tenebrio molitor has attracted wide attention in the feed industry due to its short life cycle,strong reproductive ability,high nutritional value,balanced amino acids and rich in functional substances such as vitamins,chitosan and antimicrobial peptides.Therefore,this paper took Micropterus salmoides as the experimental object,measured the apparent digestibility of M.salmoides to Tenebrio molitor meal,studied the effects of Tenebrio molitor meal replacing fish meal on the growth,body composition,liver health and intestinal barrier function of M.salmoides,and discussed the feasibility of Tenebrio molitor meal application in M.salmoides compound feed,aiming to provide technical data for the optimization of M.salmoides feed formula.1.Apparent digestibility of Micropterus salmoides to Tenebrio molitor mealThe aim of this study was to determine and compare the apparent digestibility of M.salmoides to nutrients in Tenebrio molitor meal.The experimental feed was prepared by the method of "70%basic feed+30%raw material to be tested",and 0.5%chromium trioxide（Cr₂O₃）was used as the exogenous indicator.Seventy-two first-instar M.salmoides with an average body weight of（158.9±1.9）g were randomly divided into 2 groups with 3 replicates per group and 12 fish per replicate.The fecal matter of the experimental fish was collected by siphon method for 20 days after 12 days of culture in the indoor circular culture system（feeding the basal diet for 7 days followed by feeding the experimental diet for 5 days）.The results showed that the apparent digestibility of dry matter,crude protein and ether extract of M.salmoides to Tenebrio molitor meal was 74.66%,91.09%and 90.91%,respectively.The apparent digestibility of amino acids of M.salmoides to Tenebrio molitor meal was higher than 90%.2.Effects of replacing fish meal with Tenebrio molitor meal on growth,feed utilization,liver health and intestinal barrier of Micropterus salmoidesTo evaluate the feasibility of replacing fish meal with Tenebrio molitor meal,five isonitrogen-isolipid experimental diets（TM0（control）,TM12,TM24,TM36,TM48）.M.salmoides（initial body weight 10.99±0.01g）was fed the system for 11 weeks.The results showed that with the increase of TM replacement level,final body weight（FBW）,the weight gain rate（WGR）and specific growth rate（SGR）were significantly of Micropterus salmoides increased and then decreased,and reached the highest in TM24 group.The relative expression levels of liver protein metabolism genes（PI3K,m TOR,4EBP2 and GOT）in TM24 group were significantly higher than those in other groups（P<0.05）.The activities of glutathione peroxidase（GSH-PX）and catalase（CAT）in liver were firstly increased and then decreased with the increase of TM level,while the content of malondialdehyde（MDA）in TM48 group was the highest（P<0.05）.With the increase of TM level,the relative expression levels of liver anti-inflammatory factors（IL-10,TGF-β）were first up-regulated and then down-regulated,while the pro-inflammatory factors（IL-8,IL-1β）showed the opposite trend.The liver histomorphology in TM24 group of M.salmoides was more uniform and ruddy-colored than that in the control group,and the liver nuclei were arranged neatly and clearly defined.In addition,the activities of Trypsin,lipase（LPS）and Na+,K+-ATPase were firstly increased and then decreased with the increase of TM level（P<0.05）.the relative expression of Occludin and ZO-1 in intestinal tract and the contents of D-lactic acid（D-lac）and endotoxin（ET）in serum in TM24 group were better than those in other groups.At the same time,it was observed that Tenebrio molitor meal did not affect the abundance of intestinal flora of M.salmoides,but increased the abundance of potential probiotics Lactobacillus,Lactococcus,and Wesseria at the genus level,and decreased the abundance of some potential harmful bacteria Helicobacter.In conclusion,with WGR as the criterion,the regression analysis of broken line model showed that the optimal replacement level of Tenebrio molitor meal in diets of 19.52%could enhance the antioxidant capacity and immunity of M.salmoides,regulate the intestinal physical barrier and intestinal flora structure,and improve the liver function of M.salmoides.However,high levels of fish meal replacement could damage the liver and intestinal health of M.salmoides and inhibit the growth of M.salmoides.Therefore,the Tenebrio molitor meal can be used as a high quality protein source for M.salmoides feed.