Effect of two-doses of 3-Nitrooxypropanol (3-NOP) on methane emissions, performance, rumen microbiome, and metabolomics in Nellore cattle

This study evaluated the effects of two doses of 3-nitrooxypropanol (3-NOP) on methane (CH4) emissions, performance, dry matter (DM) intake, apparent digestibility, rumen microbiome and metabolomic profile of Nellore cattle fed a high concentrate finishing finishing diet. Seventy-five 20-month-old Nellore bulls, 361.6 ± 30.08 kg body weight (BW) were individually housed with ad libitum access to feed and water. Animals were distributed in a completely randomized study design, with three treatments and 25 animals per treatment, which were: 1) CON, control (basal diet + mineral premix without 3-NOP), 2) 3-NOP65 (Basal diet + mineral premix + 65 mg 3-NOP/kg of DM), 3) 3-NOP85 (Basal diet + mineral premix + 85 mg 3-NOP/kg of DM). The 115-day trial included a 3-week adaptation period with increasing dietary concentrate levels from 50% to 88%. Enteric CH4 emissions were measured using the sulfur hexafluoride (SF6) tracer gas technique. Supplementation with 3-NOP had no detrimental effect on final BW (P = 0.89) and average daily gain (ADG; P = 0.94), but DM intake increased linearly with 3-NOP inclusion (P = 0.05). Methane emissions (g/d) were reduced by 13.2% and 26.7% in the 3-NOP65 and 3-NOP85 groups, respectively (P < 0.05), without adverse effects on animal health. Rumen microbiome analysis revealed a quadratic response in the relative abundance of the phylum Euryarchaeota (P = 0.01). Metabolomic analysis indicated significant changes in amino acid and energy metabolism, with proline, arginine, and threonine identified as key discriminant metabolites (VIP > 1) in the 3-NOP85 group. These findings demonstrate that 3-NOP supplementation effectively reduces CH4 emissions in a dose-dependent manner, while maintaining animal performance and health.