| Due to the shortage of fishmeal resources and rising prices,the use of plant protein sources as alternative to fishmeal is receiving widespread attention.However,plant protein sources are poorly utilized by aquatic animals and are prone to produce intestinal damage and oxidative stress.Therefore,functional nutrients may be an effective way to improve the utilization of non-fishmeal protein sources.Sodium butyrate is a promising functional additive,and it has attracted more attention in recent years.This study investigated the effects of sodium butyrate supplementation in low fishmeal feeds on the growth performance,serum biochemical parameters and intestinal health of rainbow trout(Oncorhynchus mykiss)and largemouth bass(Micropterus salmoides),respectively.The results could provide theoretical basis for the application of sodium butyrate in aquafeeds.1 Effects of dietary sodium butyrate on the growth,nutrient utilization,intestinal histology and microbiota of rainbow trout(Oncorhynchus mykiss)The study investigated the effects of dietary sodium butyrate(SB)on the growth performance,nutrient utilization,intestinal histology and microbiota of rainbow trout(Oncorhynchus mykiss).A high fishmeal diet and a low fishmeal diet were formulated to contain 200 g/kg or 100 g/kg fishmeal,respectively.Coated SB(50%)was supplemented to each of the diets at levels of 0,1.0 and 2.0 g/kg to create 6 diets.The diets were fed to rainbow trout with initial body weight of 29.9 ± 0.2 g for 8 weeks.Compared to the high fishmeal group,the low fishmeal group showed significantly lower weight gain(WG),intestine muscle thickness,and significantly higher feed conversion ratio(FCR),amylase activity(P<0.05).The supplementation of SB in high or low fishmeal diet did not significantly affect the WG,FCR,protein retention and the digestibility of dry matter andcrude protein(P>0.05).The supplementation of 2.0 g/kg SB in low fishmeal diet significantly increased the villus height,villus width and muscular thickness,while the supplementation of 2.0 g/kg SB in high fishmeal diet also significantly increased the intestinal villus height(P<0.05).In intestinal microbiota,the supplementation of 2.0 g/kg SB significantly increased the abundance of Proteobacteria and Aeromonas,and decreased the abundance of Firmicutes and Mycoplasma(P<0.05),but the flora at genus and phylum level were not affected by SB supplementation in low fishmeal diet(P>0.05).In conclusion,the addition of SB in diets containing 100 or 200 g/kg fishmeal did not enhance the growth performance and nutrient utilization of rainbow trout,but improved intestinal morphology and changed intestinal microbial flora.2 Effects of sodium butyrate in low fishmeal diet on the growth,serum biochemical parameters,intestinal histology and microbiota of large-size largemouth bass(Micropterus salmoides)This study investigated the effects of adding two sodium butyrate in diets on the growth,serum biochemical indexes,intestinal histology and microbiota of large-size largemouth bass.A positive control diet(PC)with fishmeal content of 350 g/kg was designed,and a negative control diet(NC)with fishmeal content of 245 g/kg was obtained by replacing 30% of fishmeal with cottonseed protein concentrate.Then,1.0 and 2.0 g/kg of sodium butyrate products of A and C with different coating material were added to the negative control diet,respectively.The above six diets were fed to large-size largemouth bass with initial body weight of 70.2 ± 0.1 g for 8 weeks.The results showed no significant differences in weight gain(WG),feed conversion ratio(FCR),villus height,muscle thickness and intestinal digestive enzyme activities between the NC and PC group(P>0.05),while serum diamine oxidase activity in NC groups was significantly higher and villus width was significantly lower(P<0.05)than those in the PC group(P<0.05).The addition of both sodium butyrate in NC diet significantly decreased D-lactate content,diamine oxidase and lipase activities and increased villus height(P<0.05),but did not significantly affect the growth performance(P>0.05).The addition of 1.0 g/kg sodium butyrate A or C to NC diet significantly increased lysozyme activity(P<0.05),and 2.0g/kg sodium butyrate A or C addition significantly decreased amylase activity(P<0.05).The analysis of intestinal microorganisms showed that both sodium butyrates significantly increased the relative abundance of Fusobacteriota and Cetobacterium,decreased the relative abundance of Proteobacteria,Plesiomonasand and Aeromonas(P<0.05).In conclusion,the addition of 1.0 and 2.0 g/kg sodium butyrate to low fish meal diets did not significantly affect the growth performance of large-size largemouth bass,but increased the intestinal villus height,promoted the proliferation of Fusobacteriota and Cetobacteriumand and decreased the abundance of Proteobacteria,Plesiomonas and Aeromonas.3 Effects of dietary sodium butyrate on the growth,serum biochemical parameters,intestinal histology and microbiota of small-size largemouth bass(Micropterus salmoides)This study investigated the effects of dietary sodium butyrate on the growth performance,serum biochemical indexes,intestinal digestive enzyme activity,histomorphology and microorganisms of small-size largemouth bass.A control diet(Con)with fishmeal content of 320 g/kg was designed,then 2.0,4.0,8.0,12.0 and 16.0 g/kg of sodium butyrate(Na B-2,Na B-4,Na B-8,Na B-12 and Na B-16)was added to the control diet to form six diets.The six diets were used to feed small-size largemouth bass(2.4±0.0 g)for 8 weeks.There were no significant differences in weight gain(WG)and feed conversion ratio(FCR)among all the groups except that Na B-16 group showed a significantly lower WG than the Con group(P<0.05).No significant differences in morphological indices and whole body composition were detected among all the groups(P>0.05).In terms of serum biochemical indices,alkaline phosphatase and lysozyme activities were significantly higher in the sodium butyrate treated groups(P<0.05),and D-lactate content was significantly lower in the Na B-12 group(P<0.05)than those in the control.All the groups presented the similar values of malondialdehyde,superoxide dismutase,glutathione peroxidase,acid phosphatase,diamine oxidase activity,amylase,trypsin activity and total antioxidant capacity(P>0.05),while the Na B-2 and Na B-4 groups showed significantly higher lipase activity than the control group(P<0.05).In terms of intestinal histology,there was no significant difference in villi height and muscle layer thickness in between sodium butyrate-added groups and the Con group(P>0.05),while villi width in Na B-8 group was significantly higher(P<0.05).Compared to the Con group,the relative abundance of Frimicutes and Mycoplasma was significantly increased and the relative abundance of Proteobacteria,Achromobacter and Plesiomonas was significantly decreased in Na B-4 and Na B-16 groups(P<0.05).In conclusion,the dietary addition of sodium butyrate did not promote the growth of small-size largemouth bass,but decreased the relative abundance of Proteobacteria and Plesiomonas in the intestinal tract. |
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