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

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