Methane emissions from Nellore young bulls fed supplements with additives during the rainy season

This trial aimed to evaluate the methane emissions from Nellore young bulls receiving daily supplementation of 0.3% of the BW, housed in 12 paddocks of Brachiaria cv. 'Xara?s', in the rainy season. The use of additives in supplementation seeks to maximize the symbiotic relationship of microorganisms present in the rumen, improving ruminal fermentation process and maximizing feed efficiency, thus contributing to a better performance in the growth phase and termination. The diets were: supplement without additives (SUP), with Monensin (SUPM - 80 mg/kg), with Virginiamycin (SUPV - 150 mg/kg) and supplement with Monensin and Virginiamycin (SUPMV - 80 and 150 mg/kg, respectively). Thirty-two animals with an average weight of 478 ? 32.45 kg and 24 months old were used for evaluation. Methane emissions were measured using the sulphur hexafluoride (SF6) tracer technique, where each animal was sampled daily for five consecutive days, beginning at 126 d of feeding. The DMI was estimated through the use of internal and external indicators (iNDF and Chromium Oxide, respectively). The weight gain was calculated according to the initial and final weigh both fasting, carcass gain was calculated according to the income reference slaughtering and final slaughtering. Data were analyzed using the Proc Mixed of SAS with a randomly design (5% of probability). No differences were found for g CH4/d (SUP = 112.94, SUPM =111.50, SUPV = 109.50, SUPMV = 119.08; P = 0.28), kg CH4/year (SUP = 41.22, SUPM = 40.70, SUPV = 40.05, SUPMV = 43.47; P = 0.28), g CH4/kg DMI (SUP = 9.57, SUPM = 9.35, SUPV = 9.78, SUPMV = 10.15; P = 0.73), g CH4/kg ADG (SUP = 120.24, SUPM =116.78, SUPV = 110.34, SUPMV = 113.32; P = 0.58) and g CH4/kg CG (SUP = 265.79, SUPM =294.99, SUPV = 239.97, SUPMV = 225.16; P = 0.07). The use of additives in supplementation did not affect the methane enteric emissions of Nellore bulls finished in pasture at the rainy season.