| The abuse of antibiotics and other pharmaceutical feed additives has caused great harm to the livestock and poultry industry.So it is important to find a non-toxic and harmless alternative to antibiotics.As a kind of probiotics,Bacillus subtilis has become a research hotspot due to its unique biological characteristics.In this paper,the biological characteristics of Bacillus subtilis 513 N isolated from the laboratory were studied to verify the possibility of its application in feed;The fermentation medium of B.subtilis 513 N was optimized;The effects of B.subtilis 513 N on growth performance,antioxidant capacity,immunity and intestinal flora of chicks were analyzed.The results are as follows:1.Biological characteristics of B.subtilis 513N: in the fermentation process,B.subtilis513 N was delayed from 0 to 4 h,entered the logarithmic growth period from 4 to 12 h,and entered the stable period from 22 to 26 h.B.subtilis 513 N was treated in water bath at80 °C for 10 min,and the survival rate reached 80.2%.However,when the temperature rose to 90 °C,the survival rate decreased to 59.3 %.The survival rate of B.subtilis 513 N was 60.3% after 12 h of artificial gastric juice culture with p H2.After culture for 12 h with0.3% bile salt concentration,the survival rate was 57.6%.2.Study on the optimization of fermentation medium of B.subtilis 513N: the optimized fermentation medium was prepared with corn flour 1.48%,soybean meal powder 1.90%,glucose 0.44%,Na Cl 1%,Mg SO4 0.05%,K2HPO4 0.2%,KH2PO4 0.2%.After optimization,the number of viable bacteria reached 12.16×109CFU/m L.3.Effect of B.subtilis 513 N on chicks: compared with the control group,the low dose,medium dose and high dose groups could significantly increase the daily weight gain,end weight,tibial length and antibody titer levels of ND,H9 and H7N9 in chicks(P<0.05).The influence of spleen index and bursa index of each group was not significant(P>0.05).Compared with the control group,the levels of albumin(ALB)and globulin(GLB)in the blood were significantly increased in the medium-dose group and high-dose group(P<0.05),while the levels of high-density lipoprotein cholesterol(T-AOC)were significantly increased in the high-dose group(P<0.05).Compared with the control group,the total antioxidant capacity(T-AOC)and superoxide dismutase(SOD)activities inspleen and liver of the medium dose group and the high dose group were significantly increased(P<0.05).Compared with the control group,the high-dose group has more abundant bacterial diversity,and the abundance of Bifidobacterium,Lactobacillus,Faecalibacterium and Butyricicoccus is higher,Erysipelatoclostridium,Eisenbergiella,Subdoligranulum and Lachnoclostridium are less abundant. |
