Characterization of goat rumen-derived isolates and their effects on in vitro ruminal fermentation properties

The goat rumen bacterial community is a potential source of probiotics, the impact of which on the microbial community when administered is unclear. Four isolates obtained from adult goat rumens were identified as Enterococcus sp. (isolate 11), Streptococcus sp. (isolates 14 and 7), and Pediococcus sp. (isolate B). A batch culture system was used to evaluate the effects of these four isolates at three inoculation levels on in vitro rumen fermentation characteristics, rumen microbial community composition, and predicted functional profiles. Compared to the control fermentation, the inclusion of any isolate reduced the pH, acetate proportion, and acetate-to-propionate ratio, while increasing the total volatile fatty acid (VFA) concentration and propionate proportion (PA%). Isolates 11 and 14 increased total gas production compared to the control, whereas Isolate B showed the lowest pH, highest PA%, and total VFA concentration. The microbial community structure was strongly influenced by the inclusions. Functional prediction of the community determined differential pathways related to metabolic activity. In particular, isolate B (Pediococcus sp.) yielded the highest relative abundance of Xylanibacter and Prevotella, ultimate carbohydrate-metabolizing members toward a greater representation, may have enhanced the predicted functional potential for the metabolism of multiple sugars, resulting in increased VFA production. Isolates 11 (Enterococcus sp.) and 14 (Streptococcus sp.) were mainly associated with enhanced fermentation activity and showed enrichment in fiber-metabolizing bacteria compared to the inclusion of other isolates. Although the supplementary effect on specific bacterial taxa was minor, the inclusion of isolates enriched different predicted pathways and showed a convergent potential for enhancing VFA production. The inclusion of these isolates enhanced in vitro rumen fermentation and modulated the microbial community, implying beneficial effects on animal feeding applications, with each strain exhibiting unique benefits.