Measurement of Enteric Methane Emissions by the SF6 Technique Is Not Affected by Ambient Weather Conditions.

Peter J Moate,Leah C Marett,Jennie E Pryce,Brigid E Ribaux,William J Wales,Matthew H Deighton,Josie B Garner,Murray C Hannah,S Richard O Williams

doi:10.3390/ani11020528

Abstract

Simple SummaryAlthough the SF6 technique was developed over 25 years ago with the intention that it could be used to measure enteric methane production from ruminants outdoors, no experiments have reported the influence of ambient wind speed, temperature, humidity or rainfall on the accuracy of the technique. Six different cohorts of dairy cows (40 per cohort) were kept outdoors and fed a common diet during spring in 3 consecutive years. Individual cow feed intakes and daily methane productions were measured over 5 consecutive days and an automatic weather station measured air temperature, wind speed, relative humidity and rainfall every 10 min. Regression analyses were used to relate the average daily temperature, wind speed, humidity and rainfall to the average daily dry matter intake, methane production and methane yield of each cohort of cows. It was concluded that the modified SF6 technique can be used outdoors during a range of weather conditions without a significant effect on the measurement of methane production or methane yield of dairy cows.Despite the fact that the sulphur hexafluoride (SF6) tracer technique was developed over 25 years ago to measure methane production from grazing and non-housed animals, no studies have specifically investigated whether ambient wind speed, temperature, relative humidity and rainfall influence the accuracy of the method. The aim of this research was to investigate how these weather factors influence the measurement of enteric methane production by the SF6 technique. Six different cohorts of dairy cows (40 per cohort) were kept outdoors and fed a common diet during spring in 3 consecutive years. Methane production from individual cows was measured daily over the last 5 days of each 32-day period. An automated weather station measured air temperature, wind speed, relative humidity and rainfall every 10 min. Regression analyses were used to relate the average daily wind speed, average daily temperature, average daily relative humidity and total daily rainfall measurements to dry matter intake, average daily methane production and methane yield of each cohort of cows. It was concluded that the modified SF6 technique can be used outdoors during a range of wind speeds, ambient temperatures, relative humidities and rainfall conditions without causing a significant effect on the measurement of methane production or methane yield of dairy cows.

Highlights

There are five main methods used to measure daily methane production (MeP, g/day) and methane yield (MeY, g/kg dry matter intake)
Due to the limited sampling times used in these latter methods [5], and the marked diurnal patterns in the magnitude of mean of production (MeP) from dairy cows [6], some researchers have questioned the suitability of these recent methods for quantifying daily MeP of individual cows [7,8]
Proxy methods for estimating daily MeP or MeY of individual animals are numerous, including predictions based on dry matter intake (DMI) [9], feed composition [10], methane to carbon dioxide ratio in breath [11], milk fatty acids [12], and volatile fatty acids in ruminal fluid [13]

Summary

Introduction

There are five main methods used to measure daily methane production (MeP, g/day) and methane yield (MeY, g/kg dry matter intake). Due to the limited sampling times used in these latter methods [5], and the marked diurnal patterns in the magnitude of MeP from dairy cows [6], some researchers have questioned the suitability of these recent methods for quantifying daily MeP of individual cows [7,8]. Proxy methods for estimating daily MeP or MeY of individual animals are numerous, including predictions based on dry matter intake (DMI) [9], feed composition [10], methane to carbon dioxide ratio in breath [11], milk fatty acids [12], and volatile fatty acids in ruminal fluid [13]. Proxy methods have generally had poor predictive accuracy and have limited applicability in terms of predicting

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Discussion

Conclusion