Effects of Polymeric Media-Coated Gynosaponin on Microbial Abundance, Rumen Fermentation Properties and Methanogenesis in Xinjiang Goats

SIMPLE SUMMARY: Saponins are famous for their anti-methane effects; however, due to their structural differences that have different fates of antimicrobial activity in the rumen, their effects are not consistent in the literature. Thus, the current study used polymeric media-coated gynosaponin (PMCG) to estimate the time-dependent effects on the methanogenesis, rumen fermentation properties and microbial abundance in goats. We used Xinjiang goats (n = 8) that were divided into two groups, i.e., the PMCG group (8 g/kg DMI) and a control group (0 g/kg DMI). Ruminal contents were analyzed for rumen fermentation properties and microbial abundance. Protozoa numbers were counted to calculate the abundance of methanogens, rumen fungi and cellulolytic bacteria using real-time PCR. The results indicated that PMCG significantly reduced the methane production, and decreased the acetate to propionate ratio and total VFA concentration. The protozoa numbers and gene copies of methanogens, total bacteria and F. succinogens relative to the 16 s rDNA were all slightly decreased. Overall, the addition of PMCG had an inhibitory effect on methane production. ABSTRACT: Gynosaponin is known to modulate rumen methanogenesis and microbial fermentation characteristics in ruminants. The current experiment aimed to determine the time-dependent effects of intraruminal polymeric media-coated gynosaponin (PMCG) supplementation on the methanogenesis, rumen fermentation properties and microbial abundance in Xinjiang goats. Eight goats were used in a 2 × 2 crossover arrangement with a PMCG group (8 g/kg DMI) and a control group (0 g/kg DMI). The experiment was divided into four phases, each lasted 21 d. Ruminal contents were obtained for analysis of rumen fermentation properties and microbial abundance. Protozoa numbers were counted by microscope and the abundance of methanogens, rumen fungi and cellulolytic bacteria were quantified by real-time PCR. The results indicated that PMCG significantly reduced methane production (p < 0.05) during the first two phases but this increased to baseline again during the last two phases. Meanwhile, the concentration of acetate decreased remarkably, which resulted in a significant reduction in the acetate to propionate ratio and total VFA concentration (p < 0.05). However, other rumen properties and dry matter intake were not affected (p > 0.05). During the first and second phases, the protozoa numbers and gene copies of methanogens, total bacteria and F. succinogens relative to the 16 s rDNA were all slightly decreased, but the statistical results were not significant. However, the ruminal supplementation of PMCG had little effect on other tested microbes. Accordingly, it was concluded that the addition of PMCG had an inhibitory effect on methane production probably due to a decline in methanogen numbers.