Effects Of Bacillus Subtilis And Antibiotic Growth Promoters On Growth Performance And Gut Functions Of 0-6 Weeks Pullets

Bacillus Subtilis and antibiotic growth promoters(AGP)can both present the growth promoting effect through their interaction with intestine,but there are few studies focus on their interaction and mechanism.This study was conducted on 0~6 weeks pullets by a two-factor experiment design to analysis the main effects of Bacillus Subtilis and AGP as well as their interactions on the growth performance and gut function parameters.Exp.1 Effects of Bacillus Subtilis and AGP on growth performance and body development of0~6 weeks pulletsThis experiment aims to study the main effect of the Bacillus Subtilis and AGP on growth performance and body development of 0~6 weeks pullets.In total 544 birds were used and these were subjected to 4 treatments with 7 replicates,18 birds each replicate.The feeding experiment lasted for 6 weeks and the treatments were designed as follows:Negative control group with basal diet;AGP group with Bacitracin Zinc 20 mg/kg and Colistin Sulphate 4 mg/kg into basal diet,BS group with Bacillus Subtilis of 500g/t;and the Mix group with both Bacitracin Zinc 20 mg/kg and Colistin Sulphate 4 mg/kg and Bacillus Subtilis of 500g/t.The results showed that: Bacillus Subtilis has significant effect on growth promoting by reducing the feed conversion ratio of the 4th to 6th week period.Bacillus Subtilis and AGP showed no significant effect on immune organ indexes of the 3rd and 6th week pullets.However,Bacillus Subtilis and AGP showed an interaction on the spleen index of the 6th week.There present no significant effect of both Bacillus Subtilis and AGP on immune organ indexes and weight homogeneity as well as interactions.So,we can draw a conclusion that Bacillus Subtilis can improve the growth performance by the 4th to 6th week period,while AGP didn’t effect the growth performance of 0~6 weeks pullets.The interaction of these two factors only present on the spleen index of the 3rd week.Exp.2 Effects of Bacillus Subtilis and AGP on gut functions of 0~6 weeks pulletsThis experiment aims to study the main effect of the Bacillus Subtilis and AGP on gut functions of 0~6 weeks pullets.The experimental design was the same as that in Exp.1.The results showed that,the effect of Bacillus Subtilis reduced the crypt depth of the duodenumand jejunum of the 3rd week pullets,improve the villus height and the villus crypt ratio of jejunum.While the effect of AGP improve the villus height of the ileum of the 3rd week.And no interactions was observed on intestinal morphology.Bacillus Subtilis could improve the gene expression of sucrase in duodenum of the 3rd week and in jejunum of 6th week.AGP could reduced the gene expression of sucrase in duodenum of the 3rd week,and improve the gene expression of aminopeptidase and maltase of the 3rd week,as well as maltase and sucrase of 6th week in ileum.However,no significant effect was observed on barrier function protein and SIgA concentration of of 0~6 weeks pullets as well as interactions.So we can conclude that Bacillus Subtilis could improve the morphology and enzyme gene expression of duodenum and jejunum,while AGP mainly improve the functions of ileum.