Dietary hydrolysed tannins regulate carcass performance and meat traits in Hu sheep through microbial regulation

Tannins improve ruminants' growth and production performance via promoting nitrogen utilisation or as antioxidants and antiparasitic agents. However, the metabolism and effectiveness of tannins on ruminal microbiota and biohydrogenation and consequently regulating meat fatty acid composition of sheep are always unclear. So, the objective of this study was to determine the effect of a 20 g/kg DM tannic acid addition on the meat quality of the longissimus lumborum (LL) muscle as well as the slaughter performance of Hu sheep. Additionally, the study sought to evaluate the potential influence of the rumen microbiota by measuring its composition. A cohort of 36 Hu sheep exhibiting normal development was randomly assigned to two groups: the control group, which received a basal diet, and the tannic acid group (TAN), which received a basal diet supplemented with 20 g/kg DM tannic acid (75 days). The results revealed significant enhancements in the preslaughter live weight and carcass weight of Hu sheep in the TAN group (P < 0.05). It is worth noting that the inclusion of tannic acid in the diet resulted in a significant reduction of 2.89% (P = 0.009) in the cooking loss of LL muscle. Regarding the colour of the flesh, the terminal pH (P = 0.003) and L* (lightness) (P = 0.002) values of the LL muscle exhibited a significant decrease in the TAN group. Tannic acid diet addition altered the rumen microbiota, with Firmicutes (P = 0.014) becoming more abundant and Bacteroidota (P < 0.001) less abundant in the TAN group at the phylum level and in positive proportion to n-3 polyunsaturated fatty acids in LL meat. At the genus level, Acetitomaculum (P = 0.008) became more abundant and was positively correlated with monounsaturated fatty acids in LL muscles, while Prevotella (P = 0.033) decreased in abundance. The findings of our study indicate that the incorporation of 20 g/kg DM tannic acid into the diet resulted in a notable augmentation in the concentration of short-chain fatty acids within the rumen, as well as inducing alterations in the composition of the rumen microbiota. For example, altered Acetitomaculum and Muribacter flora play a key role in promoting the regulation of the unsaturated fatty acid composition of LL muscle. thereby altering the fatty acid structure of lean muscle and ultimately enhancing lean meat quality.