Effects of dietary supplementing tannic acid on methane production, rumen fermentation, rumen microflora and nutrient digestion of Liuyang black goats.

Objective: This study investigated the effects of dietary tannic acid on methane production, nutrient digestibility, rumen fermentation, and rumen microbiota in Liuyang black goats.

Methods: Twelve adult goats were randomly assigned to two groups: a control group (CON) and a treatment group (TAN) that received 2 % tannic acid in their diet. The experiment had two stages, each with a 10 - day adaptation and a 5 - day sampling phase. Methane emission was measured using a mobile open-circuit respirometry system, while rumen fluid samples were analyzed for volatile fatty acids (VFAs), ammonia nitrogen, and microbial composition via 16S rRNA sequencing.

Results: The results indicated that the tannic acid significantly reduced overall methane emission (p < 0.05), methane per voluntary feed intake (VFI, p < 0.05), dry matter intake (DMI, p < 0.05), acid detergent fiber intake (ADFI, p < 0.05), and neutral detergent fiber intake (NDFI, p < 0.05). Microbial analysis showed increased relative abundance of Firmicutes (p < 0.05) and decreased Methanobrevibacter and Prevotella. Tannic acid also improved ADF digestibility (p < 0.05) and altered VFA profiles by increasing acetic acid to propionic acid ratios and valeric and butyric acids (p < 0.05). Tannic acid supplementation also increases the ratios of acetic acid to propionic acid, as well as valeric and butyric acids (p < 0.05), while increasing the digestibility of ADF (p < 0.05).

Conclusion: Dietary tannic acid effectively reduced methane emission and enhanced feed efficiency in Liuyang black goats by modifying rumen fermentation and microbial activity. These findings suggest tannic acid's potential as a sustainable feed additive for ruminants, although long-term impacts on health and productivity require further investigation.