0376 Estimating enteric methane and carbon dioxide emission from lactating dairy cows using GreenFeed system

Abstract

Enteric methane (CH4) and carbon dioxide (CO2) emissions from lactating dairy cows vary over time depending on various factors that include feed intake, feeding strategy, diet composition, and the time of day. GreenFeed system (C-Lock Inc., Rapid City, SD) is an on-farm “bait station” that captures the breath of cattle when they visit and quantitatively analyzes the emitted gasses for CH4 and CO2 flux. The objective of this study was to determine the correlation between measurements of CH4 and CO2 at 2 selected time points of the day vs. 8 equally spaced time points over the 24 h in the diurnal cycle. A GreenFeed system was placed at the University of Alberta-Dairy Research and Technology Center in an open area and cows were moved from their stalls to the unit during measurement time. Individual average daily CH4 and CO2 emissions were estimated from lactating dairy cows (N = 29) varying from 32–76 average days in milk (DIM). Individual daily CH4 and CO2 emissions were estimated 2 times a day (09:00–12:00; 18:00–20:30 h) for 14 consecutive days and then emissions were measured on the same cows at 8 equally spaced time points (0200, 0500, 0800, 1100, 1400, 1700, 2000, and 2300 h) in the diurnal cycle within 2–3 d. The two time points during the day included the higher and the lower peaks in the diurnal pattern of CH4 and CO2 emissions. The number of visits during the 2 times a day and over 24 h measurement ranged from 11–31 and 2–8, respectively. Daily individual CH4 and CO2 emissions were estimated by averaging visit fluxes and extrapolating over a day. The result showed a strong correlation of dry matter intake (r = 0.73; P < 0.001), CH4 g/d (r = 0.74; P < 0.001) and CO2 g/d (r = 0.72; P < 0.001) production between 2 times vs. 8 time-point measurements. The Pearson correlation coefficient for CH4 yield (g/kg of DMI) also showed moderate correlation (r = 0.41; P < 0.05) between the two measurements. Taken together, daily CH4 and CO2 emissions can be estimated with lower frequency of sampling per day as long as the minimum and maximum emission points in the diurnal cycle are included with an adequate number of visits.