| In this study,L.vannamei and Epinephelus were selected as research objects.The study were investigated the effects of Lactobacillus acidophilus and Bacillus subtilis on growth,enzyme activity,and m RNA expression-related enzymes in shrimp and grouper,respectively.Four experiments were included to study:1.An 8-week feeding trial was carried out to investigate the effects of Lactobacillus acidophilus on growth performance,nonspecific immune enzyme activities,resistance to disease and m RNA expression of related enzymes for juvenile Litopenaeus vannamei.A total of 840 L.vannamei with initial average weight of(0.58±0.01)g were random Ly assigned into 7 groups in triplicates with 40 individuals per replicate.Seven isonitrogenous and isolipid diets were supplemented with 0%,0.1%,0.2%,0.4%,0.6%,0.8%,1.0% Lactobacillus acidophilus,respectively,in a basal diet.The results showed as follows: WGR,SGR increased gradually as dietary L.acidophilus increased up to 0.4%,and then showed decline trend(P<0.05).The minimum FCR were occurred in feed supplement with 0.2% L.acidophilus,significantly lower than other groups(P<0.05),while PER showed the opposite results.Serum PO,AKP and ACP activities increased gradually as incremental dietary L.acidophilus levels,and then gradual decline.The maximum values of PO,AKP,ACP were found in 0.4%,0.1%,0.2% group respectively(P<0.05).Activities of serum CAT,LZM and SOD of all treatment groups in fish were signficantly higher than that of control group(P<0.05).Gene expression levels of CAT,LZM of all treatment groups in fish were signficantly up-regulated than that of control group(P<0.05).At the end of feeding trail,shrimps were challenged by Vibrio harveyi for 96 h.Post challenge survival rate increased as increasing dietary L.acidophilus levels(P<0.05).Based on the broken-line regression analysis of WGR,when feed supplemented with 0.23%(0.72×108cfu/m L)of L.acidophilus could significantly improve growth and nonspecific immunity of juvenile Litopenaeus vannamei.2.The effects of dietary Lactobacillus acidophilus on growth performance,digestive enzyme activities,premunition and related enzyme gene m RNA expression of Epinephelus coiodes were studied in this experiment.Seven hundred and twenty healthy grouper with an average body weight of(5.60 ± 0.05)g were random Ly divided into 8 groups with 3 replicates per group and 30 fish per replicate.The fish in the control group and experimental group were fed a basal diet and an experimental diet(the basal diet and experimental diet supplemented with L.acidophilus at the percentage of 0,0.1,0.2,0.4,0.6,0.8,1.0 and 1.2%),respectively.The experiment lasted for 8 weeks.The results showed that: the WGR and SGR increased first and then decreased with the adding amount increasing,but they were significantly higher than those of the control group(P<0.05).The FCR reached the lowest value in 0.6% group and significant lower than other group(P<0.05).However,the PER level showed an opposite trend to the FCR.The activities of TRY and AMY in the liver and intestine tended to increase first and decreased thereafter.The TRY and AMY m RNA level of liver in the experimental group was significantly higher than that in the control group(P<0.05).The results showed that the survival rate of the fish significantly increased with the increase of the dosage of Vibrio harvey for 7 days(P<0.05).On the basis of WGR,according to the broken line model,it was concluded that 0.42% Lactobacillus acidophilus(0.72 × 108 cfu/m L)in the feed could significantly promote the growth and increase the digestive enzyme activity for juvenile grouper.3.The effects of dietary Bacillus subtilis on growth performance,nonspecific immune enzyme activity and related enzyme gene m RNA expression of Litopeneaus vannamei under low fishmeal diet were studied in this experiment.Nine hundred and sixty healthy shrimp with an average body weight of(0.40 ± 0.01)g were random Ly divided into 8 groups(two control groups and experiment groups)with 3 replicates per group and 30 fish per replicate.The low and high fishmeal group included 10% and 20% fishmeal,respectively.The shrimp in the control group and experimental group were fed a basal diet and an experimental diet(the basal diet and experimental diet supplemented with B.subtilis at the percentage of 0,0,0.1,0.25,0.5,0.75,1.0 and 1.25%),respectively.The experiment lasted for 8 weeks.The results showed that: the WGR and SGR increased first and then decreased with the addition in the diets,but they were significantly higher than those of low fish meal group and lower than those of high fish meal group(P<0.05).The FCR reached the lowest at the 0.75% addition level,the other groups were significantly lower than the low fish meal group and higher than the high fish meal group(P<0.05),but the tendency of PER was contrary to the FCR.The activities of phenol oxide enzyme,acid phosphatase,CAT and LZM increased first and then decreased.The activities of alkaline phosphatase and superoxide dismutase were significantly higher than those of low fish meal group and lower than those of high fish meal group(P<0.05).The m RNA expression of CAT and LZM increased first and then decreased,in the same time,the experimental group was significantly higher than that in the low fish meal group and lower than that in the high fish mela group(P<0.05).The SR of Litopeneaus vannamei significantly increased(P<0.05)with the addition of Vibrio harvey for 96 h.On the basis of WGR,according to the broken line model,it was concluded that the addition of 0.73% B.subtilis(1.0×108cfu/m L)to feed of Litopeneaus vannamei with low fish meal(soybean meal replacing 10% fish meal)could significantly promote the growth of Litopeneaus vannamei and improve its disease resistance,non-specific immune enzyme activities and its m RNA expression level.4.The purpose of this experiment was to investigate the effect of Bacillus subtilis on growth performance,digestive enzyme activity,antioxidant enzyme activity and m RNA expression of juveniles,Epinephelus lanceolatu?×Epinephelus fuscoguttatus?.A total of 720 grouper with average initial weight of(7.00 ± 0.02g)were random Ly assigned into 8 groups in triplicates with 30 individuals per replicate.Eight isonitrogenous and isolipidic diets were prepared by adding 0%(negative control group),0.1%,0.25%,0.5%,0.75%,1.0%,1.25% Bacillus subtilis in a diet with low fish meal(15%),and were formulated by a high fishmeal group(35%)as positive control group.The results showed that : the WGR and SGR were increased firstly and then decreased with the Bacillus subtilis level increasing(P<0.05).The FCR in 0.75% group has the lowest value(P<0.05),while the PER showed the opposite trend comparing to FCR.The activities of TRY and AMY firstly increased and then decreased(P<0.05).The activities of serum CAT and SOD in 0.75% group has the maximum value(P<0.05).The highest CAT and GR m RNA expression in liver of fish were observed in 0.5% and 0.75% group,respectively(P<0.05).Grouper were challenged by Vibrio harveyi for 7 days,the survival rate of grouper increased significantly with the Bacillus subtilis level increasing(P<0.05).It can be concluded that the supplementation of 0.63% B.subtilis(1.0×108 cfu/m L)can significantly enhance the growth performance,disease resistance,digestive enzymes,serum CAT and SOD activity and m RNA expression related to immunity of grouper,which is estimated with WGR as the evaluation index. |
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