PSXIII-23 Increasing levels of a tannin-based product on performance, rumen microbiome and enteric methane emission of Nellore cattle finished in feedlot.

Abstract This study aimed to evaluate the effects of low dosages of tannin-based product tannin supplementation on the performance, methane emissions, and rumen microbiome of Nellore cattle in a feedlot system. A total of 98 uncastrated male Nellore cattle were randomly assigned to four treatments: 1) CON: Negative control (basal diet without feed additives); 2) TAN08: Basal diet + 0.8 g/kg of DM of a tannin-based product; 3) TAN16: Basal diet + 0.16 g/kg of DM of tannin-based; and 4)TAN32: Basal diet + 0.32 g/kg of DM of tannin-based product. The tannin-based product was composed of quebracho, and chestnut tannin extracts along with carriers from cereals rich in saponins; SilvaFeed BX, Silvafeed®. The diet consisted of 82% concentrate and 18% forage (DM basis). Animals were housed in four collective pens, each equipped with four automated Intergado® feeders to record individual feed and water intake. Animals were weighed after 12 hours of fasting on the beginning (d0) and last d of the experiment (d 133). Data was analyzed as a completely randomized design by fitting a generalized linear mixed model (GLIMMIX procedure) and considering treatment as a fixed factor, and animal as random. Continuous outcome variables were by using least square difference test and polynomial linear regressions for additive levels. Animal performance results indicated that DMI linearly increased with tannin supplementation, particularly in the TAN32 group (P = 0.02). Average daily gain (ADG) quadratically increased with TAN16 presenting the highest value (P = 0.04), 1.203 g/d vs. 1.053 g/d, for TAN16 and CON, respectively. Despite not difference observed in hot carcass weight this increase and ADG for TAN16 compared to control resulted in 3.6% increase in hot carcass weight for TAN16 compared to CON. Methane emissions were significantly reduced in the TAN32 group compared to the control diet (P = 0.02), with a linear reduction in CH4 total emissions (g/d), intensity (CH4/HCW), and in CH4 emissions per unit of dry matter intake (CH4/DMI, P < 0.05), demonstrating the potential of tannins to mitigate enteric methane emissions up to 20% when compared to CON. Rumen microbiota analysis revealed shifts in bacterial composition, with a reduction in the genus CF231 (Paraprevotellaceae) and an increase in Roseburia in TAN16 and TAN32. Furthermore, a significant linear reduction on the relative abundance of methanobrevibacter with the increasing levels of TAN. In conclusion, tannin supplementation in Nellore cattle finishing diets increased ADG, leading to a slight increase in HCW. Notably, tannins significantly reduce methane emissions, especially at 16 and 32 g/animal/d, and alter the rumen microbiota, reducing methanogenic archaea like Methanobrevibacter. These results suggest tannins can enhance environmental sustainability in beef cattle production.