Plant-derived additives mitigate in-vitro methane emissions without impairing ruminal fermentation in high-concentrate beef cattle diets

Introduction Optimizing ruminal fermentation and mitigating methane (CH 4 ) emissions are critical strategies for enhancing energetic efficiency and sustainability in intensive beef cattle production. As regulatory bans on conventional growth promoters increase, natural plant-derived compounds and exogenous enzymes have emerged as viable alternatives for rumen modulation. Methods This study evaluated the effects of plant-derived additives and fibrolytic enzymes on in vitro ruminal fermentation, gas production kinetics, and CH 4 emissions in a high-concentrate beef cattle diet. Eight treatments were tested in a completely randomized design using a 48-h in vitro gas production system with four independent fermentation batches (n = 4). Treatments included a basal diet (10:90 roughage:concentrate, DM basis) supplemented with essential oils (0.1 or 0.3 g/kg DM), sugarcane polyphenols (0.25 or 0.50 g/kg DM), tannins (0.50 g/kg DM), a polyphenol–tannin combination, fibrolytic enzymes (0.25 g/kg DM), or no additive (control). Results Essential oils increased ( P < 0.05) lag time and in vitro organic matter digestibility (IVOMD) while decreasing ruminal pH ( P < 0.001). Polyphenols at 0.50 g/kg DM had the greatest CH 4 reduction, decreasing CH 4 production from 6.81 to 3.77 mmol per incubation bottle and from 71.3 to 38.2 mmol/g OMD compared with the control, equivalent to a 46% reduction ( P < 0.001), expressed per unit of DM, organic matter (OM), or digested OM. All other additives reduced ( P < 0.05) CH 4 production by approximately 28–32% without impairing fermentation characteristics. The combination of polyphenols and tannins increased propionate proportion ( P = 0.03). Discussion Overall, plant-derived additives and fibrolytic enzymes reduced enteric CH4 emissions in high-concentrate diets without detrimental effects on ruminal fermentation, with sugarcane polyphenols showing the greatest mitigation potential.