Enteric Methane Emissions from Holstein Cows Grazing Kikuyu Grass in the Colombian High Tropics During Two Seasons

Enteric methane emissions (EMEs) from grazing dairy systems in tropical regions remain poorly quantified, increasing uncertainty in national greenhouse gas inventories. This study aimed to quantify EMEs using electronic spirometry masks (ESMs) in dairy cows in the Colombian high tropics during two precipitation seasons in two adjacent milk production management systems. Six cows of a high-milk-yield management system (HMYMS; >30 L/d) and six cows of a low-milk-yield management system (LMYMS; <15 L/d) grazing kikuyu grass (Cenchrus clandestinus) and supplemented with concentrate feed were monitored by EMEs, exhaled air volume, feed intake, milk yield and composition. Data were analyzed in a 2 × 2 factorial arrangement (season × production system). Season affected kikuyu chemical composition (p < 0.05) but not dry matter intake (DMI), milk production, quality, nor EMEs (p > 0.05). However, the absence of seasonal effects on these variables may be due to the sample size. Although HMY cows had a higher DMI (kg DM/d; p < 0.01) and EME (g/d, L/d; p < 0.05), they exhibited a lower methane intensity (both, L/L milk yield and L/kg fat-corrected milk) and gross energy intake lost as methane (p < 0.05). Positive correlations were found between EMEs 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.