Effects Of Lactic Acid Bacteria And Yeast Added To Feed On The Growth And Immunity Of Crucian Carp Carassius Auratus

Crucian carp(Carassius auratus)is a traditional culture fish in China.At present,due to the serious environmental pollution of aquaculture,frequent fish diseases,and the abuse of antibiotics,the cost of crucian carp culture increases,and the safety of aquatic products can not be guaranteed.Adding probiotics to the water enviroment or feed can improve the water quality,promote the fish growth,strengthen the fish body immunity,and save the culture cost.Therefore,in this experiment,lactic acid bacteria and yeast separated from water enviroment were used to ferment soybean meal and determine the nutritional value and live bacteria number of the formented soybean meal.Then the crucian carps were fed with different diets in which the dietary soybean meal were replaced with the fermented soybean meal to evaluate effects of fermented soybean meal with lactic acid bacteria,yeast or mixed strains on the growth performance,muscle nutrients and quality,immunity and intestinal flora diversity of the fish for its pratical application in crucian carp production.The main results are as follows:(1)Experiment 1,preparation of fermented soybean meal with lactic acid bacteria and yeast.The soybean meal were fermented with different microorganisms and 1 kg soybean was inoculated with 40 ml broth containing lactic acid bacteria 2.88×10~9cfu/m L(LAB),yeast solution 2.96×10~9cfu/m L(YE)or mixture of the two strains(lactic acid bacteria:yeast=1:1)(LAB＿YE).The fermentation contidions were at 28℃,37%moisture,and fermentation for 3days.The results showed that compared with control group,the crude fat contents of LAB,YE and LAB＿YE groups were significantly increased(P<0.05),and while crude ash,crude protein,amino acid and fatty acid content were no significant different(P>0.05).(2)Experiment 2,effect of diets containing fermented soybean meal on the growth performance and muscle nutritional composition of crucian carp.The experimental crucian carp(14.61±0.12)g in average body weight were divided into four groups(30 fish/group)randomly and each group had three replicates.The fish were fed with different diets in which the dietary soybean meal were replaced with the fermented soybean meal for eight weeks.The results showed that compared with control group,the crude fat and DHA content were significantly higher in LAB and YE groups(P<0.05),the content of crude protein,EPA,DHA and n-3 PUFA in fish muscles of LAB＿YE group was significantly increased(P<0.05),and no significant differences were found in the growth performance and amino acid content of crucian carp in LAB,YE and LAB＿YE groups.The above results show that soybean meal fermented with the mixture of lactic acid bacteria and yeast is better than single strain in the muscle quality of crucian carp.(3)Experiment 3,effect of diets containing fermented soybean meal on the immune physiology of crucian carp.With crucian carp(14.61±0.12)g as the research object,the fish were fed with different diets in which the dietary soybean meal were replaced with the fermented soybean meal for eight weeks.The results showed that compared with control group,the activity of SOD,LZM,ACP and AKP of crucian carp in LAB,YE and LAB＿YE groups were significantly improved(P<0.05),among which LAB＿YE had the highest SOD and ACP activity,while the intestinal flora diversity of crucian carp in LAB＿YE was significantly improved;The tissue section results showed that both lactic acid bacteria and yeast can alleviate the vacuolization phenomenon of the hepatopancreas of the crucian carp,and the lactic acid bacteria obviously improved the intestinal health of the crucian carp,but the yeast has no obvious impact on the crucian carp intestine;The relative expression of il-1βm RNA in LAB,YE and LAB＿YE groups was significantly higher than control group(P<0.05),and tgf-βm RNA was significantly lower than control group(P<0.05),but there was no significant difference between the experimental groups(P>0.05),only the relative expression of the il-8 and ifn-γm RNA were significantly increased in LAB＿YE group(P<0.05);There was no significant change in growth-related genes in LAB,YE and LAB＿YE groups(P>0.05).The above results show that soybean meal fermented with the mixture of lactic acid bacteria and yeast is better than single strain in the immune physiology of crucian carp.