Enteric Methane Emissions from Holstein Cows Grazing Kikuyu (Cenchrus clandestinus) Grass in a Herd in Colombian High Tropic at Two Seasons of the Year

Enteric methane emissions (EME) from grazing dairy systems in tropical regions remain poorly quantified, increasing uncertainty in national greenhouse gas inventories. This study aimed to quantify EME using electronic spirometry masks (ESM) in dairy cows in Colombian high tropics during two precipitation seasons. Six high milk yield (HMY; >30 L/d) and six low milk yield (LMY; <15 L/d) grazing kikuyu grass (Cenchrus clandestinus) and supplement with concentrate feed were monitored by EME, exhaled air volume, feed intake, milk yield and composition. Data was analyzed in a 2 × 2 factorial arrangement (season × production level). Season affected Kikuyu chemical composition (P< 0.05) but not dry matter intake (DMI), milk production, quality, nor EME (P > 0.05). Despite HMY cows having a greater DMI (kg DM/d; P < 0.01) and EME (g/d, L/d; P < 0.05) exhibited lower methane intensity (g / kg fat-corrected milk) and gross energy intake lost as methane (P < 0.05). Positive correlations were found between EME and total dry matter intake (r = 0.638) and milk production (r = 0.726). The observed methane yield was comparable to previous studies for tropical kikuyu-based systems but lower than reports from temperate regions, suggesting seasonal-driven kikuyu quality does not translate into EME changes in high tropic regions. Animal productivity level was a key driver of EME magnitude and efficiency, effectively measured by ESM which may represent a practical tool for narrowing EME estimates for tropical pasture-based dairy systems.