Effects Of The Sodium Butyrate Or Lactoferrin Addition In High Soybean Meal Diets On The Growth Performance And Intestinal Health Of Grouper(Epinephelus Coioides)

A feeding trial was conducted to investigate whether sodium butyrate or lactoferrin addition in high soybean meal diets alleviate the enteritis caused by soybean meal(SBM)in grouper.The control diet(FM diet)was formulated to contain 48% protein and 11% fat.Soybean meal was used to replace 60 % fish meal protein in FM diet to prepare soybean meal ditet(SBM60 diet).Sodium butyrate at 0.1%,0.2%,and 0.3% or lactoferrin at 0.2%,0.6%,and 1.0% were added to the SBM60 diet to prepare six experimental diets and numbered as NBT0.1,NBT0.2,NBT0.3 for Sodium butyrate and LTF0.2,LTF0.6,and LTF1.0 for lactoferrin,respectively.The fish with an initial weight of 33.34 g were randomly divided into 24 tanks,30 fish per tank.Eight experimental groups of fish with triplicate tanks were fed to apparent satiety twice daily during a feeding period of eight weeks.The main results are as follows:1.Effects of dietary sodium butyrate addition on the growth and intestinal health of grouper.With the increase of sodium butyrate addition level in feed,weight gain rate(WGR)and specific growth rate(SGR)increased first and then decreased,and intestinal glutathion peroxidase(GSH-Px)activity,trypsin and protease activity showed a gradual upward trend,and all the addition groups were significantly higher than those in the SBM60 group(P<0.05).Intestinal malondialdehyde(MDA)content,plasma D-lactic acid(D-Lac)and endotoxin(ET)content,complement 3(C3)and immunoglobulin M(Ig M)content decreased with the increase of addition level,and all addition groups were significantly lower than SBM60 group(P<0.05).The plasma low density lipoprotein cholesterol(LDL-C)content showed a downward trend,and all the addition levels were significantly lower than those in the FM group(P>0.05).The LDL-C content of NBT0.3 group was significantly lower than that of SBM60 group(P<0.05).The LDL-C content of NBT0.1and NBT0.2 had no significant difference with SBM60 group(P>0.05).The feed efficiency(FE),hepatosomatic index(HSI),condition factor(CF),body composition,plasma high density lipoprotein cholesterol(HDL-C),triglyceride(TG),total cholesterol(TC),immunoglobulin A(Ig A),diamine oxidase(DAO)activity,endothelin-1(ET-1)content,intestinal superoxide dismutase(SOD),total antioxidant capacity(T-AOC),lipase and amylase activity were not affected by both the dietary addition levels(P>0.05).The addition level of feed did not affect the height of foregut mucosal folds,the number of mucosal folds and the thickness of muscular layer(P>0.05),but the height of midgut mucosal folds and the thickness of muscular layer increased with the increase of the addition level.The height of midgut mucosal folds and the thickness of muscular layer in all the addition groups were significantly higher than those in the SBM60 group(P<0.05).The thickness of hindgut muscle layer showed an upward trend,and all the addition groups were significantly higher than those in the SBM60 group(P<0.05).With the increase of feed addition level,the m RNA levels of intestinal IL-8,IL-1β,IL-12 and TNF-α decreased,while the m RNA levels of intestinal IL-10 and TGF-1βincreased.The intestinal IL-8,IL-1β,IL-12 and TNF-α m RNA levels in the addition group were significantly lower than those in the SBM60 group(P<0.05).2.Effects of dietary lactoferrin addition on the growth and intestinal health of grouper.With the increase of lactoferrin addition level,WGR,SGR,intestinal GSH-Px activity,trypsin and protease activity showed an upward trend.The addition level was significantly higher than that in the SBM60 group(P<0.05),and the intestinal protease content reached the maximum in the LTF1.0 group.The intestinal MDA content,plasma D-Lac,ET,C3 and Ig M contents decreased with the increase of the addition level,and all the addition groups were significantly lower than those in the SBM60 group(P<0.05),but the plasma D-Lac and ET contents in the LTF0.2 and LTF1.0 groups were significantly lower than those in the FM group(P<0.05).The plasma LDL-C content showed a downward trend,and all the addition levels were significantly lower than those in the FM group(P>0.05).The LDL-C content of LTF0.6 and LTF1.0 group was significantly lower than that of SBM60 group(P<0.05).The LDL-C content of LTF0.2 had no significant difference with SBM60 group(P>0.05).The FE,HIS,CF,body composition,plasma HDL-C,TG,TC and Ig A,DAO activity,ET-1 content,intestinal SOD,T-AOC,lipase and amylase activity were not affected by adding levels(P>0.05).The addition level of feed did not affect the height,number and thickness of foregut mucosal folds(P>0.05),but the height and thickness of midgut mucosal folds increased with the increase of the addition level.The height and thickness of midgut mucosal folds in all the addition groups were significantly higher than those in the SBM60 group(P<0.05),and were more obvious in the LTF0.2 group.The thickness of hindgut muscle layer showed an upward trend,and all the addition groups were significantly higher than those in the SBM60 group(P<0.05).With the increase of feed addition level,the m RNA levels of intestinal IL-8,IL-1β,IL-12 and TNF-α decreased,while the m RNA levels of intestinal IL-10 and TGF-1β increased.The m RNA levels of IL-8,IL-1β,IL-12 and TNF-α in the intestine of the adding group were significantly lower than those of the SBM60 group(P<0.05).The m RNA levels of IL-10 and TGF-1β in the intestine of the adding group were significantly higher than those of the FM group and the SBM60 group.The above results from the present study showed that the addition of sodium butyrate or lactoferrin in the high soybean meal diets could improve intestinal morphology,reduce intestinal mucosal permeability,and maintain relatively high trypsin activity and immune capacity,thus alleviating the inflammatory reaction of grouper caused by high soybean meal diet.However,sodium butyrate or lactoferrin did not affect intestinal microbial profile in grouper.