PSII-B-13 Bacterial Composition of the Rumen Microbiome with a Bacillus Probiotic Added to the Diet of Feedlot Cattle

Abstract

Abstract The threat of the development of an antibiotic resistant bacterium necessitates investigation for alternative feed additives. Probiotics are known to confer a health benefit to the animal and affect the production of the animal through increased nutrient digestibility. The aim of this study was to investigate the bacterial composition of the rumen of South African feedlot cattle when supplemented with a Bacillus probiotic. Twenty-four Bonsmara cattle were randomly divided into two groups: a basal diet (control, CTR) and the basal diet supplemented with Bacillus-based probiotic (B. licheniformis and B. subtilis; Bovacillus, Chr. Hansen A/S; BOV). The animals were fed for 120-days divided by starter, grower, and finisher diets. Four animals from each group were selected for rumen content collection via stomach tube during each phase. DNA extraction was performed and submitted for 16S rRNA sequencing (V3-V4). Approximately 41 300 ASVs were identified from 87 genera using DADA2, phyloseq and the RDP database. ANOSIM was used to determine different microbial profiles and Wilcoxon Rank Sum test to determine significant differences in the relative abundance of the microbes between the treatment groups. Microbial profiles in the starter (ANOSIM=0.0416) and grower (ANOSIM=0.1771) phases were similar between CTR and BOV. Most bacteria had greater abundance in CON compared with BOV in the starter phase. In the grower, BOV had a significantly greater abundance of Prevotella (p=0.028) and Lachnobacterium (p=0.042) compared to CTR. The microbial profiles between CTR and BOV differed in the finisher phase (ANOSIM=0.3229) with most of the bacteria having a significantly greater abundance in BOV compared with CTR including Roseburia (p=0.028), Fibrobacter (p=0.057) and Ruminococcus (p=0.028). These microbes as well as Prevotella are known fiber-degraders in the rumen microbiome. The results indicate a tendency in BOV for increased abundance of fibre-degrading microbes, however further studies are needed to validate these findings.