| Our country’s aquaculture industry is developing rapidly,and there is a huge demand for feed,but the supply of fishmeal has not significantly increased,which is far from meeting the needs of the aquaculture industry.The global fishmeal market as a whole shows a trend of short supply,and China’s fishmeal import dependence is relatively serious.The replacement of fish meal with vegetable protein is an important issue in aquaculture.We propose whether it is possible for fish to change from passively accepting vegetable protein to actively adapting through early vegetable protein nutrition planning.Therefore,this study used paraffin sections,enzyme activity determination,qRT-PCR and other technologies to analyze the growth,morphology,intestinal digestive enzymes,histological indicators,inflammatory factors,tight junction proteins,and amino acid transport of yellow catfish under early plant protein nutrition planning.The relative expression levels of the vector and the key factors of the mTOR signaling pathway were analyzed to explore the effect of early nutritional planning on the utilization of yellow catfish plant protein.In the experiment,fish meal(FM)and soybean meal(SBM)were used as the main feed protein sources,and two feeds were prepared.The feeding period is 142 days.The experiment was divided into 3 stages,namely,early short-term soybean meal(SBM)feed stimulation,restoration of fish meal(FM)feeding,and late soybean meal(SBM)re-feeding.In this experiment,SBM feed was administered to stimulate early short-term feeding between the 13th day(13dph,13 days post hatching)and 23 dph after hatching the membrane of yellow catfish,and FM feed was used as the positive control group(Phase 1);Afterwards,switch to FM feed for 37 days(Phase 2);then start the third phase of SBM refeeding test(Phase 3,Phase 4),at this time,divide the FM and SBM groups into 2 treatment groups.FM and SBM were fed separately,and the yellow catfish fed with FM throughout the course was used as the control group(FM-FM).Sampling was performed at the end of each stage and at the later stage of SBM feeding in the middle and end stages,sampling a total of 4 times.The main results of this test are as follows:(1)The effect of early nutritional planning on the survival rate,specific growth rate,morphology and body composition of Pelteobagrus fulvidracoEarly nutrition planning has no significant effect on the survival rate of yellow catfish;regardless of whether early nutrition planning is carried out,SBM feeding can significantly reduce the SGR of yellow catfish;The content of crude ash and crude fat in SBM-FM group was significantly higher than that in FM-SBM and SBM-SBM groups;early nutrition planning has no significant effect on moisture and crude protein content.In the middle stage of soybean meal refeeding,ILI-I and ILI-II in the SBM-SBM group were not significantly different from those in the FM-FM group.At the end stage,ILI-I and ILI-II were not significantly different from those in the FM-FM group.At the end stage,CF,ILI-I and ILI-II were significantly higher in the SBM-SBM group than in the FM-FM group.SBM stimulated feeding promoted the lengthening of the intestine of yellow catfish.(2)The effect of early nutritional planning on the digestive physiology of yellow catfishIn the early stage of stimulation of soybean meal,compared with the FM group,the activities of LPS,trypsin and amylase in the visceral mass of yellow catfish larvae and juveniles in the SBM group were significantly reduced,and the activity of AKP was significantly increased.No significant effect on ACP activity.Compared with the FM group,the expression level of y+LAT2 mRNA in the visceral mass of yellow catfish in the SBM group was significantly increased.After resuming the fish meal feeding,compared with the FM group,the activities of LPS,trypsin,amylase and AKP in the liver of SBM group of yellow catfish were significantly increased.The activities of liver ACP and intestinal trypsin,AKP and ACP were significantly reduced in the SBM group.Compared with the FM-FM group,the SBM-SBM group had significantly higher expression levels of the amino acid transporter B0AT1,y+LAT1 and y+LA T2 in the intestine of yellow catfish.In the refeeding stage of soybean meal,no matter in the middle or the final stage,the liver LPS activity in the FM-SBM and SBM-SBM groups was significantly higher than that in the FM-FM and SBM-FM groups.SBM feeding stimulated the liver LPS activity.When soybean meal was fed again in the middle stage,the activities of LPS,AKP and ACP in the SBM-SBM group were significantly lower than those in the SBM-FM group;compared with the SBM-FM group,the intestinal trypsin of the yellow catfish in the SBM-SBM group.The activity is significantly increased.At the end of soybean meal re-feeding,compared with the SBM-FM group,the activities of trypsin,amylase and ACP in the liver of SBM-SBM group were significantly increased.In the foregut tissues,the LPS,trypsin and ACP activities of the FM-SBM group were significantly higher than those of the FM-FM,SBM-FM and SBM-SBM groups.The AKP activity was the highest in the FM-FM group.Significantly higher than the FM-SBM,SBM-FM,SBM-SBM group.Early nutrition planning had no significant effect on midgut LPS,trypsin,and AKP activities at the end of soybean meal refeeding.The hindgut LPS activity of SBM-FM group was significantly lower than that of FM-FM,FM-SBM and SBM-SBM groups;the hindgut AKP activity of SBM-SBM group was significantly higher than that of FM-FM,FM-SBM,SBM-FM group.Compared with the FM-FM and SBM-FM groups,the ACP activity of the hindgut of the FM-SBM and SBM-SBM groups was significantly reduced.At the end of re-feeding soybean meal,compared with the FM-FM group,the FM-SBM,SBM-FM,and SBM-SBM groups of yellow catfish foregut amino acid transporter y+LAT2 mRNA expression levels were significantly increased;in the midgut and hindgut tissues,the y+LAT2 mRNA expression level in FM-SBM,SBM-FM and SBM-SBM groups was significantly lower than that in FM-FM.The expression level of y+LAT1 mRNA in the midgut and hindgut FM-SBM group was significantly lower than that in the FM-FM group.The expression levels of FM-SBM,SBM-FM and SBM-SBM B0AT1 in each intestinal segment of yellow catfish were significantly lower than those in the FM-FM group.Early nutritional planning may improve the digestion and absorption function of the foregut of yellow catfish.(3)The effect of early nutritional planning on the intestinal tissue structure,inflammatory factors and tight junction proteins of yellow catfishAfter early soybean meal stimulation,compared with the FM group,the intestinal structure of the SBM group was higher than the intestinal mucosal folds,and the development of IL-12,IL-10,Claudin-3 and Occludin mRNA expression levels were significantly increased in the SBM group.After resuming fish meal feeding,compared with the FM group,the expression levels of IL-10,Claudin-7,Claudin-12,Claudin-15 and Occludin mRNA in the intestine of SBM group were significantly increased,and TNF-α was significantly decreased.Histological indicators showed that,compared with the FM-FM group,the number of goblet cells,the thickness of the muscle layer and the submucosa were significantly increased in the foregut and hindgut of the SBM-SBM group.At the end of soybean meal refeeding,compared with the FM-FM group,the height/width of mucosal folds in the foregut and hindgut tissues of the SBM-SBM group were significantly reduced;Compared with the FM-FM group,the SBM-SBM group had lower foregut and mid-intestinal colitis parameter scores,but increased in the hindgut.At the end stage,compared with the FM-FM group,the SBM-SBM group yellow catfish pro-inflammatory factor IL-12 mRNA expression levels increased significantly in the foregut and hindgut,and decreased significantly in the midgut;NF-κB mRNA expression level in the FM-SBM group was significantly higher than that in the FM-FM,SBM-FM and SBM-SBM groups;the TNF-α mRNA expression level in the foregut was significantly higher than that in the FM-FM,SBM-FM and SBM-SBM groups.There was no significant difference in the midgut and hindgut;compared with the FM-FM group,the anti-inflammatory factor IL-10 mRNA expression level was significantly reduced in each intestinal segment of yellow catfish.The expression level of Claudin mRNA showed an overall upward trend in the foregut,and significantly decreased in the midgut and hindgut.Early nutritional planning may aggravate the inflammatory response in the hindgut of yellow catfish,and improve the ability of the yellow catfish to adapt to plant protein in the midgut.(4)The effect of early nutritional planning on the mRNA expression of key factors in the mTOR signaling pathway in yellow catfishAfter early soybean meal stimulation,compared with the FM group,the expression level of 4E-BP1 mRNA in the visceral mass of yellow catfish increased in the SBM group.After resuming fishmeal feeding,compared with the FM group,the expression levels of AKT and S6K1 mRNA in the SBM group were significantly increased and decreased,respectively.Compared with the FM-FM group,the S6K1 mRNA expression level in the midgut increased significantly and the 4E-BP1 mRNA expression level decreased significantly in the mid-term soybean meal refeeding;in the foregut at the end,the S6K1 mRNA expression level increased significantly.The expression level of 4E-BP1 mRNA was significantly reduced.Early nutritional planning has an impact on the expression of key factors in the mTOR signaling pathway of yellow catfish.Early nutritional planning may affect the expression of key factors in the mTOR signaling pathway to improve the fish’s later adaptation to plant proteins.In summary,from the perspective of the intestinal enzyme activity,intestinal histology and expression of amino acid transporters,inflammatory factors,epithelial tight junction proteins,and mRNA expression levels of key factors in the mTOR signaling pathway,We believe that early plant protein nutrition planning for 13dph yellow catfish may improve the digestion and absorption of plant protein in the foregut tissue,improve the adaptability of the midgut to plant protein,and have an unsatisfactory effect on the hindgut tissue.Early nutritional planning may be a strategy of lengthening the intestines to improve the body’s digestion and absorption of plant protein.Early plant protein nutrition program has a regulatory effect on mTOR signaling pathway. |
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