Abstract
BackgroundBacillus spp. seem to be an alternative to antimicrobial growth promoters for improving animals’ health and performance. However, there is little information on the effect of Bacillus spp. in combination with different dietary crude protein (CP) levels on the ileal digestibility and microbiota composition. Therefore, the objective of this study was to determine the effect of Bacillus spp. supplementation to low- (LP) and high-protein diets (HP) on ileal CP and amino acid (AA) digestibility and intestinal microbiota composition.MethodsEight ileally cannulated pigs with an initial body weight of 28.5 kg were randomly allocated to a row-column design with 8 pigs and 3 periods of 16 d each. The assay diets were based on wheat-barley-soybean meal with two protein levels: LP (14% CP, as-fed) and HP diet (18% CP, as-fed). The LP and HP diets were supplemented with or without Bacillus spp. at a level of 0.04% (as-fed). The apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of CP and AA was determined. Bacterial community composition from ileal digesta was analyzed by Illumina amplicon sequencing and quantitative real-time PCR. Data were analyzed as a 2 × 2 factorial design using the GLIMMIX procedures of SAS.ResultsThe supplementation with Bacillus spp. did not affect both AID and SID of CP and AA in growing pigs. Moreover, there was no difference in AID of CP and AA between HP and LP diets, but SID of cystine, glutamic acid, glycine, and proline was lower (P < 0.05) in pigs fed the HP diets. The HP diets increased abundance of Bifidobacterium spp. and Lactobacillus spp., (P < 0.05) and by amplicon sequencing the latter was identified as predominant genus in microbiota from HP with Bacillus spp., whereas dietary supplementation of Bacillus spp. increased (P < 0.05) abundance of Roseburia spp..ConclusionsThe HP diet increased abundance of Lactobacillus spp. and Bifidobacterium spp.. The supplementation of Bacillus spp. resulted in a higher abundance of healthy gut associated bacteria without affecting ileal CP and AA digestibility, whereas LP diet may reduce the flow of undigested protein to the large intestine of pigs.
Highlights
Bacillus spp. seem to be an alternative to antimicrobial growth promoters for improving animals’ health and performance
The Bacillus spores determined in the experimental diets amounted to 1.54 × 109 Colony forming units (CFU)/kg feed for high-protein diets (HP) + and Low-protein diet (LP) + diets, whereas HP - and LP - diets contained 0.02 × 109 and 0.04 × 109 CFU/kg feed, respectively
There was no difference in apparent ileal digestibility (AID) of crude protein (CP) and amino acid (AA) between HP and LP diets, Table 3 Analyzed chemical composition and Bacillus cell numbers in assay diets
Summary
Bacillus spp. seem to be an alternative to antimicrobial growth promoters for improving animals’ health and performance. The objective of this study was to determine the effect of Bacillus spp. supplementation to low- (LP) and high-protein diets (HP) on ileal CP and amino acid (AA) digestibility and intestinal microbiota composition. Due to the ban of antimicrobial growth promoters in livestock feeding by the European Union in 2006 [1], probiotics are considered as an alternative for improving animals’ health and performance [2, 3]. Within this regard, Bacillus spp. have the ability to sporulate, thereby making them stable during thermal treatment of feed, and resistant to enzymatic digestion along the gastrointestinal tract (GIT) [4]. There is increasing evidence that interactions of supplemental probiotics with dietary CP level affect the intestinal microbiome at the ileal level [18]
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