Tannin-based product in feedlot diet as a strategy to reduce enteric methane emissions of Nellore cattle finished under tropical conditions.

A total of 120 Nellore bulls, [initial body weight (BW) = 307 ± 11.6 kg and 12 mo of age] were allocated into 12 collective pens (10 bulls per pen) in a commercial feedlot to evaluate the effects of a specific blend of tannin and saponins on enteric methane (CH 4 ) emissions. The study was a completely randomized design, in which pens were considered the experimental units ( N = 6 pens per treatment) and were randomly allocated into one of two treatments: 1) Control (CON), a basal diet with monensin supplementation (25 mg/kg dry matter [DM]; Rumensin, Elanco Animal Health, Greenfield, IN, USA), or 2) Control + a specific blend of tannin and saponins (TAN; 7 g/kg DM; composed of quebracho and chestnut tannin extracts along with carriers from cereals rich in saponins; SilvaFeed BX, Silvateam, San Michele Mondovi, CN, Italy). After the adaptation period (20 d), the experiment was divided into two phases: growing phase (21 to 53 d; total of 33 d) and fattening phase (54 to 139 d; total of 86 d). Enteric methane emissions were estimated using the sulfur hexafluoride (SF 6 ) tracer gas technique. Interactions between treatment and period (growing vs. fattening) were detected for daily CH 4 emissions, in which animals fed TAN reduced CH 4 emissions by 17.3% during the fattening period compared to bulls fed CON ( P = 0.05). In addition, bulls fed TAN had lower CH 4 emissions expressed by dry matter intake (DMI) during the fattening period compared to bulls fed CON ( P = 0.06). The findings presented herein indicate that a specific blend of tannin and saponins can be used as a strategy to reduce enteric CH 4 emissions and its intensity of Nellore bulls finished in feedlot systems under tropical conditions.