Bacillus subtilis DSM29784 modulates cecal microbiome, short chain fatty acids concentration, and apparent retention of dietary components in Shaver Whites during grower, developer and laying phases

This study investigated the efficacy of a single strain Bacillus subtilis ( SSB) on the composition of cecal microbiota and its link to the concentration of short chain fatty acids ( SCFA ) and apparent retention ( AR ) of components. A total of 720, 4-wk old Shaver White chicks were allotted to either control ( CON ), 1.1E+08 (Low, LSSB ), 2.2E+08 (Medium, MSSB ) or 1.1E+09 (High, HSSB ) CFU/kg of diet. At grower (10 wk), developer (16 wk) and laying (28 wk) phases, excreta and cecal digesta samples were taken for AR, microbial and short SCFA analyses. Microbial analysis involved high-throughput sequencing of the V3-V4 hypervariable regions of 16S rRNA gene. Bacterial diversity decreased ( P P Bacteroides and Faecalibacterium were differentially enriched in the developer for SSB- compared with CON-fed birds. Although no differences in microbial diversity were detected in grower and layer phases, different species of Clostridium ( XVIII, XIVa, IV, and XIVb )—major butyrate producers—were identified in all phases with stronger effect sizes for SSB- compared to CON-fed birds. Iso-butyric acid was elevated in dose response ( P =0.034) in layer phase. In addition, the relative abundance of Alistipes , Lactobacillus and Bifidobacterium were positively correlated ( P B. subtilis DSM29784 may selectively enrich beneficial bacterial communities, which in turn are critical in promoting growth and performance of hens. IMPORTANCE In egg-laying chickens, the trend in the move away from the cage to alternative housing systems and restriction in antimicrobial use, requires alternative approaches to maintain health and prevent diseases. There is increased research and commercial interest towards alternative gut health solutions while improving the performance and product safety in poultry production systems. One such approach, in recognition of the importance of the gut microbial community, is the use of microbes as feed supplements (such as probiotics). Unlike meat-type chickens, studies assessing the efficacy of such microbial supplements are limited for egg-laying chickens. Thus, by conducting a comprehensive assessment of the hen microbiota in response to varying level of B. subtilis DSM29784 during the pullet phase (grower and developer) and the layer phase, the current study demonstrated the importance of direct-fed microbes in modulating gut microbiome, which may relate to improved performance efficiency in the pullet and layer phases.