| With the rapid development of China’s economic level,people’s pursuit of quality of life is also gradually improving,so food safety has become the most concerned issue.Since 2020,China has banned the application of antibiotics as feed additives in animal production.With the banning of antibiotics and the increasing difficulty of developing new drugs,the demand for antibiotic alternatives is increasing.As a microorganism beneficial to the body,probiotics have shown great advantages in improving growth performance and enhancing the body’s immune function,and can partially replace antibiotics.As a kind of probiotic,Bacillus is currently widely recognized in animal production,and has become the most suitable probiotic for animal production because of its strong tolerance to extreme conditions and long-term storage.In this study,broiler chickens were studied by adding different doses of Bacillus subtilis to broiler diet to observe their effects on broiler growth performance,immune function,serum pro-inflammatory cytokine content,intestinal morphology and harmful microorganisms,which provided a theoretical basis for the application of Bacillus subtilis in broiler production.This experiment was designed by a one-way experiment in which 360 healthy white-feathered broilers with similar weight of 1 day old were selected and randomly divided into three treatment groups,with 6replicates per treatment group and 20 chickens per replicate.Among them,the first group was the control group,fed the basic diet;the trial group I and the test group II were added to the Bacillus subtilis group,and the addition amounts were 1×10~8CFU/kg and 1×10~9CFU/kg feed,respectively,the trial period was 42days,and the test results were as follows:(1)Compared with the control group,the addition of different doses of Bacillus subtilis in the diet can significantly or significantly reduce the material-to-weight ratio(FCR)(P<0.05 or P<0.01)of broilers at different day-old stages,significantly increase the average daily food intake(ADFI)and mean daily weight gain(ADG)(P<0.05)and ADG(P<0.05)of 29-42 day-old broilers at different day-old stages,and the trial group II also has a significant effect on increasing the ADG of broilers aged 15-28 days(P<0.05).(2)Compared with the control group,the addition of different doses of Bacillus subtilis can significantly increase the thymus index and serum Ig M content(P<0.05)in 14-day-old broilers,and the spleen index and serum Ig A content in broilers in the test II group(P<0.05)can also be significantly increased(P<0.01 or P<0.05)at the age of 28 days;at the age of 28 days,compared with the control group,the immune organ index and serum immunoglobulin content in the broilers in the test group were significantly or significantly increased(P<0.01 or P<0.05).At 42 days of age,the content of Ig Y in broiler broilers in the test group was significantly or significantly higher than that in the control group(P<0.05 or P<0.01),and the serum content of Ig A in the test II group was significantly increased(P<0.05).(3)At the age of 14 days,compared with the control group,there was no significant change in the levels of Newcastle disease antibodies and H9 antibodies in the broilers of each experimental group(P>0.05);at the age of 28 and 42 days,the levels of H9 antibodies in each experimental group were significantly increased(P<0.05),and the levels of Antibodies to Newcastle disease in The second group of the test group were significantly increased at 28 days of age(P<0.05).(4)Compared with the control group,the addition of different doses of Bacillus subtilis can significantly reduce the content of IL-1βin the serum of 14-day-old broiler chickens(P<0.05),the content of IL-6 and TNF-αin the serum of broiler chickens in trial II group is also significantly reduced(P<0.05);at the age of 28 days,the content of IL-6 and IFN-αin the serum of broiler chickens in each test group was significantly reduced(P<0.01),the content of TNF-αwas significantly reduced(P<0.05),and the content of IL-1βin the high-dose trial was significantly reduced(P<0.05).At the age of 42 days,the serum content of IFN-αin broilers in each experimental group was significantly reduced(P<0.05),the serum content of IL-6and TNF-αin broiler chickens in trial GROUP II was significantly reduced(P<0.01),the content of IL-1βwas significantly reduced(P<0.05),the content of IL-1βin the serum of broiler chickens in trial group I was significantly reduced(P<0.01),and the content of IL-6 and TNF-αwas significantly reduced(P<0.05).(5)At the age of 14 days,compared with the control group,the proportion of E.coli in the intestine of broiler chickens in the test GROUP II was significantly reduced(P<0.05);at the age of 28 days,compared with the control group,the addition of different doses of Bacillus subtilis significantly or significantly increased the height of intestinal villi and V/C value(P<0.01 or P<0.05),significantly reduced the proportion of E.coli(P<0.05),and the intestinal villi height and V/C value(P<0.01)of 42-day-old broiler chickens were significantly increased in each experimental group,which significantly reduced the depth of the crypt.In summary,for broilers of different day-olds,the addition of different doses of Bacillus subtilis in the diet can improve the ADG and ADFI of broilers,reduce FCR,and improve growth performance;in addition,it can also improve the immune organ index and serum immunoglobulin content,enhance the immune function of broilers,reduce the content of pro-inflammatory cytokines in serum,inhibit the occurrence of inflammatory reactions,reduce the proportion of harmful microorganisms in the intestine,improve intestinal morphology,and promote intestinal health.On the whole,adding 1×109 CFU/g group is better. |
