Development of a Facemask System for Measuring Enteric Methane and Carbon Dioxide Production in Lactating Cows

The objective of this study was to develop a facemask system and evaluate its potential for measuring enteric CH₄ and CO₂ production. Recovery tests were conducted and resulted in 99.0% (SD, 3.2) and 102.3% (SD, 2.6), respectively. An experiment was conducted and the facemask system was compared with the GF system. Five mid-lactation cows were fed a lactation diet ad libitum (Period 1) for 5 days and then fed the same diet at 90% of the ad libitum intake for 5 days (Period 2) where CH₄ and CO₂ productions were measured at the end of each period. While daily CH₄ and CO₂ productions were different (p ≤ 0.04) between Period 1 and 2, those did not differ between the methods, and no interaction between period and method was observed. A linear regression analysis indicated a good correlation for CH₄ (CCC = 0.72; RMSE = 22% of the mean) and CO₂ (CCC = 0.79; RMSE = 10% of the mean) between the facemask and the GF system, while systemic bias was observed for CO₂. In conclusion, the facemask system developed has the potential to measure CH₄ and CO₂ production from lactating cows and the measurement was similar with that from the GF system.