Effect Of Bacillus Spp. On The Apparent Digestibility, Digestive Enzyme Activity And Pattern In Ctenopharyngodon Idellus

This study was conducted on Ctenopharyngodon idellus to study the effects of different dosages of Bacillus spp. on apparent digestibility of feed nutrients and digestive enzyme activity of intestine and hepatopancreas and patterns of protease in intestine and hepatopancreas. The experimental fish were divided into four groups. The control group(Ⅰ) was fed with basal diet, the treatment groups (Ⅱ,Ⅲ,Ⅳ) were fed with basal diet supplemented with 1×108CFU/g,3×108CFU/g,5×108CFU/g Bacillus spp. respectively. The main results were showed as follows:1. After feeding for 30 days, fecal matter was collected to detect apparent digestibility of feed nutrients. Compared with the control group, the apparent digestibility of dry matter, crude protein, crude lipid, crude ash inⅡgroup, the apparent digestibility of dry matter, crude protein, crude lipid inⅢgroup and the apparent digestibility of crude protein and crude lipid inⅣgroup were all significantly higher (P<0.05), The highest apparent digestibility was detected inⅡgroup. The the best goodness of fit curve estimated equation between dosages of Bacillus spp. and apparent digestibility of nutrients was quadratic curve equation, With the increase of dosages of Bacillus spp. the apparent digestibility of nutrients of grass carp first increased and then decreased. According to calculation, the best additional dosages of Bacillus spp.for dry matter, crude protein, crude lipid, crude ash were 2.39x108CFU/g,1.69×108CFU/g,2.38×108CFU/g, 1.56×108CFU/g respectively.2. After feeding for 30 days, protease activity of the mid-gut inⅡgroup and the hepatopancreas inⅡ,Ⅲgroup were increased significantly than the control group (P<0.05); amylase activity of the fore-gut and hind-gut inⅡgroup were increased significantly than the control group (P<0.05); lipase activity of the hind-gut inⅡ,Ⅲgroup were increased significantly than the control group (P<0.05), after feeding for 60 days, the similiar results appeared. This reflected that Bacillus spp.supplemented with diets would make amylase of fore-gut, three digestive enzymes activity of mid-gut, amylase and lipase activity of hind-gut, protease activity of hepatopancreas significantly increased (P<0.05); The ingestion of 1-3×108CFU/g Bacillus spp.made the digestive enzyme activity of intestine and hepatopancreas highest, but the ingestion of 5x108CFU/g Bacillus spp. made the digestive enzyme activity of intestine and hepatopancreas decrease. This indicated with the increase of the content of Bacillus spp. the digestive enzyme activity increased to a degree and kept a stable level or decreased, with the extension of feeding time, digestive enzyme activities would not continue to rise but would decline. Two-way analysis of variance showed that protease activity of the mid-gut, hind-gut and the hepatopancreas, amylase activity of the fore-gut, mid-gut and hind-gut, lipase activity of the mid-gut and hind-gut were all significantly affected by the additional doseages of Bacillus spp.(P<0.05); protease activity and amylase activity of the hepatopancreas were significantly affected by feeding days (P<0.05).3. After feeding for 60 days, the substrate-SDS-PAGE electrophoresis was used to analyse the effect of Bacillus spp. on patterns and intensity of protease in intestine and hepatopancreas. Compared with the control group, protease zymogram in hind-gut ofⅡ,Ⅲ, IVgroup showed two more bands HP2 and HP4 with molecular masses of 24.9 KDa and 27.8KDa respectively, the intensity of bands HP5-HP9 were all significantly increased than control group; protease zymogram in mid-gut of ,Ⅲ,Ⅳgroup showed one more band MP5 with molecular masses of 32.4KDa, the intensity of bands MP2, MP4, MP6 were all significantly increased than control group; No difference on patterns were found in fore-gut and hepatopancreas, but protease zymogram in fore-gut ofⅡ,Ⅲ,Ⅳgroup showed the intensity of bands FP2, FP4-FP7 were all significantly increased than control group, protease zymogram in hepatopancreas ofⅡ,Ⅲ,Ⅳgroup showed the intensity of band LP7 was significantly increased than control group, the intensity of bands LP6, LP5, LP3 were all significantly decreased than control group. The results showed the mechanism of Bacillus spp. supplemented with diets would make the protease activity of grass carp increased was Bacillus spp. stimulated the secretion of endogeneous protease in host, and the extracellular protease of Bacillus spp.was not a major part.