| The misuse of antibiotics in animal feed may lead to antibiotic residues and bacterial resistance in animal products,posing a threat to humans.Bacillus subtilis(BS),as an important probiotic,can promote livestock and poultry production performance,enhance immune system,and maintain intestinal health.As a substitute for antibiotics,it has attracted great attention in the feed industry.In previous studies,it was found that the BC02 strain grew faster than the conventional Bacillus subtilis on the market.The purpose of this study was to investigate the effects of Bacillus subtilis BC02 on production performance,serum metabolites and intestinal health in broilers.In this experiment,480 1-day-old AA commercial broilers with similar body weight and health were selected.Randomly divided into 5 treatments,each with 6 replicates and 16 chickens per replicate.Treatment group 1 was fed with basal diet(CON);treatment group 2was fed basal diet supplemented with 100 mg/kg BS(BS100);treatment group 3 was fed basal diet supplemented with 250 mg/kg BS(BS250);treatment group 4 was fed basal diet supplemented with 500 mg/kg BS(BS500);treatment group 5 was used as a positive control group which adding 1000 mg/kg of antimicrobial lipopeptide(AL1000).The pre trial period was 7 days,and the trial period was 35 days.The results showed that:(1)Growth performance and nutrient utilization: Compared with CON,BS500 significantly decreased average daily feed intake for 0-14 days,feed/gain for 0-28 d and 0-42d(P < 0.05),while the BS group significantly decreased feed/gain for 0-14 days(P < 0.05),AL1000 significantly reduced average daily feed intake and feed/gain in broilers at 0-14 d(P< 0.05).With the increase of BS addition,average daily gain,total bore clearance rate,abdominal fat rate,chest muscle rate,leg muscle rate,glandular stomach index,and small intestine index were increased linearly at 0-14 d(P < 0.05),while average daily feed intake and feed/gain were decreased linearly at 0-14 d,feed/gain at 29-42 d,feed/gain at 0-28 d,feed/gain at 0-42 d,and spleen index were decreased linearly(P < 0.05).BS group significantly increased the apparent metabolic rates of crude protein and Arginine(P < 0.05).With the increase of BS addition,the apparent metabolic rates of crude protein,Methionine,Arginine,Histidine,and Threonine were increased linearly,while the apparent metabolic rates of ether extract,Proline,and Tyrosine were decreased linearly(P < 0.05).(2)Serum metabolites and antioxidants: Compared with CON,the BS250 and BS500 significantly increased the content of total protein in serum(P < 0.05),the BS500 significantly reduced the content of triglycerides(P < 0.05),the BS group significantly increased the content of glucose(P < 0.05),and significantly reduce the content of urea nitrogen and MDA(P < 0.05);both BS and AL1000 significantly increased the GSH content in broiler serum(P < 0.05).With the increase of BS addition,the content of total protein,glucose,and GSH in serum were increased linearly(P < 0.05),while the content of triglycerides,total cholesterol,urea nitrogen,and MDA in serum were decreased linearly(P< 0.05).(3)Intestinal health: Compared with CON group,BS500 group could significantly improve SOD activity,GSH content,and maltose activity in jejunum(P < 0.05),while BS and AL1000 significantly reduced the content of MDA in the jejunum(P < 0.05);BS significantly increased the activity of sucrase in jejunum(P < 0.05);the BS250 significantly increased the villus height of the ileum(P < 0.05),while the BS500 significantly increased the villus height and villus gland ratio of jejunum and ileum(P < 0.05);with the increase of BS addition,SOD activity,GSH content,maltase activity,sucrase activity,villus height and villus gland ratio of jejunum and ileum were increased linearly(P < 0.05),while the content of MDA were decreased linearly(P < 0.05).BS and AL1000 significantly increased the relative expression of SOD2,CAT,GPX1,Nrf2,IL-2,IL-4,IL-10,and IL-12 in jejunum(P <0.05).With the increase of BS addition,the relative expression of SOD1,SOD2,CAT,GPX1,Nrf2,IL-2,IL-4,IL-10,and IL-12 were increased linearly(P < 0.05),while the relative expression of IL-6 was decreased linearly(P < 0.05).(4)Cecal microorganisms: Compared with CON,BS250 significantly decreased the number of Megamonas(P < 0.05)in the cecum,BS500 significantly increased the number of Prevotellaceae＿UCG＿001 and Colidextribacter(P < 0.05),and the BS significantly decreased the number of Barnesiella(P < 0.05).As the amount of BS added increasing,the relative abundance of Desulfobacta,Desulfovibrio,Barnesiella and Colidextrobacter decreased linearly(P < 0.05),while the relative abundance of Prevotellaceae＿UCG＿001 were increased linearly(P < 0.05).In summary,under the conditions of this experiment,the effects of Bacillus subtilis BC02 are superior to antibacterial lipopeptides.Adding 500 mg/kg Bacillus subtilis BC02 can promote broiler production performance,improve antioxidant capacity,and improve intestinal health. |
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