Studies On Effects Of Probiotics On Growth, Development And Digestive System In Juvenile Paddlefish Polyodon Spathula

The effects of dietary supplementation of probiotics on growth performance, digestiveenzymes activities, intestinal morphology and microbiota in juvenile paddlefish (Polyodonspathula) were studied. A total of400paddlefish Polyodon spathula with physically healthand uniform size were reared in two cages and fed with a basal diet (Control group, CG) or abasal diet supplemented with commercial probiotics products which contains probiotics A（7.47×107cfu/g,5mL/kg）and probiotics B（2.23×108cfu/g,5mL/kg）(Treatment group, TG)for80days. The effects of dietary supplemented probiotics on growth performance, bodycomposition and serum biochemical parameters of paddlefish were evaluated after the feedingtrail; whole intestinal samples were collected for the detection of the intestinal digestiveenzymes activities by ultraviolet spectrophotometer colorimetric method, intestinalhistological analysis by light microscopy and intestinal microbiota structural changes byPCR-DGGE（Denaturing gradient gel electrophoresis）methods. The important results were inthe followings:1．The results indicated that the final weight in TG（296.89±86.17g/fish）was markedlyhigher than in CG（275.03±85.14g/fish）, the trunk length （24.55±2.22cm/fish）and the fulllength（47.35±3.54cm/fish）were extremely significant higher than in CG（23.55±2.33cm/fish;46.16±3.87cm/fish）,but the feed coefficient ratio was lower than in CG（2.02:2.11）,therelative weight-growth rate and the specific growth rate were respectively increase by11.24%and5.56%compared to CG; viscerosomatic index, hepatosomatic index and intestine bodyratio and the body composition of the crude protein contents,the crude fat contents,the crudeash contents and the moisture contents in muscle and liver of paddlefish were all had nosignificant difference between two groups; glutamate pyruvate transaminase(ALT) contents（200.14±35.85U/mL）and γ-glutamyl transpeptidase(γ-GT) contents（0.76±0.36U/mL）ofthe treatment group were significant lower than the control group（253.80±23.72U/mL;1.33±0.32U/mL）（P<0.05）. Based on all these results,it could be concluded that the dietaryaddition of probiotics can promote the growth proformance,enhance feed utilization andimprove the health status of paddlefish.2．Results indicated that the addition of probiotics significantly increased intestinaldigestive protease activities, and α-amylase activity in treatment group. There was no significant difference observed for lipase activity between two groups.3．Light microscopy observation demonstrated the decreases of intestinal wall thicknessand muscularis thickness in foregut,whereas contrary effects were confirmed in hindgut in TG.In addition, remarkedly significant increase was observed in folds height in foregut, as well asin midgut in TG. Submucosa thickness and folds width between two groups didn’t showsignificant differences. All above results revealed that probiotics beneficially affectedintestinal morphology.4．DGGE results of PCR-amplified16S rRNA confirmed that the the richness anddiversity of intestinal microbial species increased in TG. The similarity between thecommercial bacteria product and intestinal microbiota from foregut, midgut and hindgut ofTG was56%,53.6%and50.8%respectively, which was higher than the microbiota from CG(36.8%,46.4%and39.3%accordingly).With the same four kinds of bacterium, Firmicutes,Proteobacteria, Bacteroidetes, Fusobacteria,the quantity of bacteria in hindgut was larger thanin midgut, and later had more rich amounts than foregut. To our knowledge, this is the first invivo study to reveal the benefical effect of dietary probiotics on intestinal digestive enzymesactivities, morphology, microbiota of paddlefish. More physiological studies are needed inorder to interprete the interaction between the probiotics and healthy immune systems ofpaddlefish intestinal tract.