Effects of Oral Administration of Goat Rumen-Derived Bacterial Isolates on In Vitro and In Vivo Rumen Fermentation...

Rumen-derived isolates are promising direct-fed microbial candidates for modulating rumen fermentation in ruminants. However, the effects of goat rumen-derived isolates have not been well characterized. In this study, two experiments were conducted to evaluate the effects of supplementation with two rumen-derived isolates identified as Pediococcus sp. (PE) and Streptococcus sp. (ST) on goat rumen fermentation. In Experiment 1, each isolate was tested separately against a non-supplemented control at three levels of inoculation (10⁴, 10⁶, and 10⁸ CFU/mL) in a 24 h in vitro rumen fermentation assay. In Experiment 2, a 3 × 3 Latin square feeding trial was conducted to evaluate the effects of long-term supplementation with the selected isolates on the rumen fermentation characteristics in goats. The feeding trial consisted of three 21 d experimental periods separated by 5 d washout intervals. Goats were fed without an additive (Control) or supplemented with 1 mL of PE (10⁷ CFU/mL) or ST (10⁹ CFU/mL) at 1 mL/day. In Experiment 1, both isolates increased the proportion of propionate (PA%) and decreased the acetate-to-propionate ratio (A/P). PE significantly increased total gas and methane production. The high dose of ST significantly decreased the relative abundances of Prevotellaceae UCG-003 and Xylanibacter but increased those of Fibrobacteraceae and Fibrobacter. In Experiment 2, isolate-associated changes in microbial co-occurrence networks were evaluated, resulting in the alteration of the dominant microbial modules. Results suggest that the isolates may have influenced rumen fermentation by reshaping potential interaction patterns among rumen microorganisms. These findings indicate that rumen-derived isolates have potential as modulators of rumen fermentation in goats, and the responses to supplementation are influenced by isolate type and the supplementation level.