Effects Of Two Different Bacillus Subtilis On Growth Performance And Intestinal Health Of AA Broiler Chickens

In the past half century,antibiotics have been widely used in animal husbandry because of their low price and obvious effects,but the prolonged and extensive abuse of antibiotics has led to a host of problems,including drug residues in animals and the emergence of superbugs.In the new era of "feed prohibition,culture reduction,product no resistance ",the study of safe,environmental protection,efficient green feed additives have become the most important in the breeding industry.Numerous studies have shown that Bacillus subtilis,as a feeding probiotic,has the functions of promoting the absorption of nutrients,maintaining the stability of intestinal microecology and enhancing the immunity of the animal organism.,etc.It has been widely used in animal husbandry and breeding.The purpose of this study is to explore the potential application value of two different Bacillus subtilis in antibiotic reduction or substitution and to strengthen its application in animal production.The aim is to explore the potential application of two different Bacillus subtilis strains in antibiotic reduction or substitution and to enhance their application in animal production,providing an important theoretical basis for the search of new antibiotic substitution products and improving practical research in animal production.The effects of two different Bacillus subtilis on the performance and intestinal health of broilers were investigated.Choosing 1-day-old healthy condition and weight similar AA broiler 288,randomly divided into four treatment groups: control group,Bacillus subtilis PB6group(adding 100 mg/kg Bacillus subtilis PB6),Bacillus subtilis 29784 group(adding 100mg/kg Bacillus subtilis 29784)and enramycin group(adding 100 mg/kg 4% enramycin),six replicates per processing group,repeat 12 chickens each.The control group was fed basic diets and the experimental group added the corresponding dose of additives to the basic diet according to the corresponding treatment.The test period was 35 days,with the first stage of the trial from 1-21 days of age and the second stage from 22-35 days of age.At the beginning and end of each stage of the experiment,the weight of the broiler and the remaining feed weight were weighed by replicate to determine the growth performance of the broilers.At the end of the trial,one chicken was selected from each replicate,blood was collected from the wing vein and then bled to death from the jugular vein,and samples of serum,liver,intestinal segments and cecum surimi were collected after slaughter for the determination of various indicators.The results showed that :1)compared with the control group,The Bacillus subtilis PB6 group of Bacillus subtilis significantly increased the average body weight and average daily gain of 21 days old broilers(P<0.05),and had a tendency to significantly increase the average daily gain at 22-35 days(P=0.09),for 35 days of age,there was no significant difference in production performance(P>0.05).2)compared to the control group,Bacillus subtilis and enramycin groups significantly increased lymphocyte count and lymphocyte ratio(P<0.01),a significant increase in the total number of white blood cells in broilers aged 21 and 35 days(P<0.05);could significantly reduce the serum uric acid content of 21 and 35 days old broilers(P<0.01),showed a decreasing trend for triglycerides(P=0.09);a significant increase in serum glucose levels in 35-day-old broilers(P<0.01),had no significant effect on triglycerides(P>0.05);a significant reduction in serum endotoxin levels in broilers at 21 and 35 days of age(P<0.01),had a significant increase in serum immunoglobulin G in 21-day-old broilers(P<0.05),there was an increasing trend in serum immunoglobulin G in 35-day-old broilers(P=0.06).3)compared to the control group,dietary supplementation of Bacillus subtilis and enramycin significantly increased glutathione peroxidase activity in liver of35-day-old broilers(P<0.01)and increased lipase activity in the liver of 21-day-old broilers significantly(P<0.05).4)compared to the control group,Bacillus subtilis group and antibiotic group could significantly increase jejunal secretory immunoglobulin content of 21 and 35 days old broilers(P<0.01);dietary addition of Bacillus subtilis and enramycin could significantly increase the activity of superoxide dismutase(P<0.01),increase the activity of glutathione peroxidase(P<0.05);dietary supplementation with Bacillus subtilis 29784 and enramycin significantly increased jejunal lipase activity in 35-day-old broilers(P<0.01);dietary supplementation with bacillus and enramycin significantly increased jejunum villi length and choriocarcinoma ratio(P<0.01),significantly reduced crypt depth(P<0.01);significantly increased jejunal villi length of 35 day old broilers(P<0.05),significantly reduced crypt depth(P<0.05);at the m RNA level,Bacillus subtilis 29784 significantly increased the gene expression of intestinal ZO-1 and Occludin in 35-day-old broilers(P<0.05),Bacillus subtilis PB6 group and antibiotic group did not differ significantly;16S r DNA results showed that compared with the control group,the relative abundance of Oscillospiraceae and Rikenellaceae of Bacillus subtilis 29784 increased significantly,The Lactobacillus of Bacillus subtilis PB6 group increased significantly,α diversity results showed that Bacillus subtilis PB6 group had a tendency to increase ACE and Chao index compared with the engramycin group(P=0.05,P=0.07);the control group could significantly improve the ACE and Chao index compared with the antibiotic group(P<0.05).To sum up,adding Bacillus subtilis to feed could significantly improve the production performance of broilers,promoted the absorption and utilization of nutrients;enhanced the antioxidant ability and intestinal immune ability of broilers;protected the integrity of intestinal mucosal barrier;regulated the intestinal microecological balance,increased the abundance of cecum microorganisms and promoted intestinal health.Bacillus subtilis has some substitution value but is not a complete substitute for antibiotics.Different species of Bacillus subtilis have different characteristics of action,and the combined application of different strains of Bacillus subtilis can be considered in actual production.