The Sulphur Hexafluoride (SF₆) method was described as the most natural way of measuring methane emissions from sheep in their natural state.
The method of capturing methane emissions was on show at the recent Teagasc Sheep Open Day in Athenry, Co. Galway.
Speaking about the SF₆ technique which is pictured (below), Teagasc sheep technician, Eoin Dunne, along with PhD Walsh Scholar, Edel O’Connor told Agriland: “Our work is to get an understanding of methane output values from sheep.
“The SF₆ method gets sheep in their natural habitat. They can eat, sleep, drink and basically do what they would normally, while out grazing while their methane output is being measured on their back using the backpacks [pictured below].
“This method of capturing methane output is based on a known SF₆ gas release rate from a permeation tube into the rumen that is collecting exhaled air into an evacuated canister from the mouth of the animal throughout the day, for 24 hours.
“The tubes are orally dosed into each sheep 6-7 days before the the taking of measurements begins.
“After 24 hours, I’ll take away the canister [that you can see there on the sheep’s back] and run an analysis on it and determine the amount of methane that sheep is producing throughout the day.
“Results from the SF₆ technique have showed that a dry ewe weighing on average 70kg is producing 37g/days of methane,” he added.
According to Eoin, the disadvantage to this method is the labour intensity of it and that it only allows for small groups of animals to be measured at a time.
“To give you an example, it took us three weeks to carry out the SF₆ method on 60 sheep, so it’s quite a slow process,” he said.
“It takes 24 hours to test it out on one sheep, whereas with the portable accumulation chambers, 72 sheep can be done in one day.”
Eoin added that the SF₆ method was tried and tested in order to validate and ensure that the portable accumulation chambers were working.
Once this was confirmed, the SF₆ method was no longer being used, however it was still a point of interest on the day for farmers to see how the study has progressed.