| 1.Effects of Bacillus fermented soybean meal instead of fish meal on growth,feed utilization and digestive enzyme activity of largemouth bassIn order to study the effects of fermented soybean meal instead of fish meal on the growth,feed utilization,digestive enzyme activity of largemouth bass(Micropterus salmoides),we employed soybean meal with aerobic fermentation by Bacillus subtilis as a partial substitute for fish meal with equal nitrogen and equal energy.0%(FM group),10%(FSM10 group),15%(FSM20 group),20%(FSM30 group)and 25%(FSM40 group)of fermented soybean were respectively used for replacing 0%,10%,20%,30% and 40% fishmeal.Largemouth bass(initial weight,19.83±0.33g)were designed 5 groups,3 parallel,30 per parallel largemouth bass.The largemouth bass were fed twice a day(7:00 and 17:00)for 75 days.The results showed that:there were no differences in the feed coefficients(P>0.05),however,the final average weight and SGR of FSM20 and FSM30 groups were significantly higher than other groups(P<0.05);Proteins efficiency of each group showed no significant differences(P>0.05),Food intake of FSM group was significantly higher than FM group,protein and fat deposition rate of FSM40 group was significantly lower than other groups(P<0.05);there were no significant differences in whole fish crude protein in each group,and the maximum value appeared in FSM20 group(P<0.05).Whole fish crude fat was significantly lower than FM group;Only the dry matter digestibility of FSM30 and FSM40 groups was significantly lower than other groups(P<0.05).No difference in plumpness,but the ratio of the visceral body in FSM30 and FSM40 groups was significantly lower than that of the other groups;there were no significant differences in the activities of protease,amylase and lipase between the FSM groups and the FM groups while substituted fermented soybean meal were less than 15%.In conclusion,the growth performance,feed utilization and digestive enzyme activity of largemouth bass juveniles were the most favorable when 20%(FSM20 group)fish meal was replaced by Bacillus subtilis aerobic fermented soybean meal.2.Effect of aerobic fermentation soybean meal instead of fish meal by Bacillus subtilis on the expression of intestinal sections,intestinal microorganisms and inflammatory factors in the intestine of young bassIn order to study whether the replacement of fish meal by Bacillus subtilis aerobic fermented soybean meal would affect the intestinal health of largemouth bass juveniles,the morphology and structure of intestinal slices and the gene expression of intestinal inflammatory factors in FM group,FSM10 group,FSM20 group,FSM30 group and FSM40 group were tested,and the intestinal microorganisms in FM group,FSM10 group,FSM 20 group and FSM 40 group were tested.The test results show that:(1)With the increase of replacement level of fermented soybean meal,there were differences in muscle thickness changes in different parts of the intestine,the thickness of midgut muscle layer is different;Changes of villus length and width in FM and FSM groups are different,and there were differences in villus length and villus width(P<0.05).(2)under the premise that the intestinal microbial coverage tended to one,Species richness in FSM40 group was significantly higher than that in FM group(P<0.05);Under 15% substitution,there was a high similarity between the intestinal flora of FSM and FM group.Main flora of each test group kept dynamic balance;At the genus level,the content of Acinetobacter increased with the increase of substitution level,and the content of whale decreased.(3)In the FSM30 and FSM40 groups,IL-8and TNF-α,IL-4 and IL-10 were significantly higher than those in the basic group(P<0.05).In conclusion,when 20% fish meal was replaced by fermented soybean meal,the intestinal health of largemouth bass would not be affected.At this time,the intestinal slice structure of FSM group was less affected,the intestinal microbial structure of FSM group and FM group was similar,and the balance of inflammatory factors was not broken.3.The effect of Bacillus aerobic fermented soybean meal instead of fish meal on immunity of largemouth bassIn order to study the effect of Bacillus subtilis aerobic fermentation soybean meal instead of fish meal on the immune ability of young bass,the serum biochemical indexes,liver immune indexes and liver slice structure of FM group,FSM10 group,fsm20 group,fsm30 group and fsm40 group were tested,and the Aeromonas hydrophila was used to attack the virus after the colonization test.The test structure shows:(1)With the increase of replacement level of fermented soybean meal,serum albumin showed a trend of first increasing and then decreasing,and the maximum value appeared in FSM20 group,with no significant difference(P>0.05);Serum globulins in FSM20 and FSM30 groups were significantly higher than those in FM group;Except FSM40 group,the total protein was significantly higher than FM group,SOD in FSM30 and FSM40 groups was significantly higher than FM group(P<0.05),and MDA decreased.LZM of FSM40 was significantly higher than FM group;(2)liver cell structure of FM group was complete,arranged orderly,cell membrane boundary was obvious;FSM 10 and FSM 20 group were significantly lower than FM group,lysozyme activity of FSM 40 group was significantly higher than FM group In fsm30 group,there were more and more vacuoles,accumulation of fat in hepatocytes and shift of nuclear position;in fsm40 group,a large number of cells dissolved,and the boundary between cells began to disappear;(3)The mortality occurred at 24 hours in FM and FSM10 groups,and at 18:00 in other groups,and the mortality of fsm40 group was the highest;in the same period,the mortality of largemouth bass increased with the increase of substitution level;the mortality of fsm30 and fsm40 groups finally stabilized at 83.33%.In conclusion,when Bacillus subtilis replaces 20% fish meal,it has the least effect on the immune ability of larval bass. |
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