Greenhouse gas emissions from the agricultural sector is often associated with ruminants. But other farm animals, including horses, also emit methane, as methane is produced as a natural part of the metabolism of the feed in the animals' digestive tract.

With cattle it is well-known that the composition and digestibility of the feed have a major impact on their methane production. Whether this applies to horses is not known with certainty.  Previous studies have shown that there are fewer of the methane producing microorganisms archea in the horse's cecum compared to the rumen of ruminants. Therefore, the methane production of horses is also smaller.

"But – in general, very few methane measurements have been carried out on horses, and therefore our knowledge of methane production in horses is significantly limited compared to cattle and pigs," says Anne Louise F. Hellwing, Department of Animal and Veterinary Sciences, who is head of the new study at Aarhus University, where the methane emissions from horses will now be measured.

"Roughages is an important foundation for ensuring that horses have a well-functioning digestion and are therefore healthy. In this project, we will therefore uncover what the methane production is in horses fed with different feed rations rich in fibre, covering their need for roughages and providing the best intestinal health," Anne Louise F. Hellwing explains.

In the national calculations of emissions of greenhouse gases from DCE (Danish Centre For Environment And Energy), 2.5% of all energy in the horse's feed is considered to end up as methane. However, a recent study from the Netherlands suggests that the loss of methane could be less than the value used in national calculations. "However, we expect that fibre-rich rations, which are preferable in relation to the horse's gut health, will also contribute with most methane, as it is the degradation and decomposition of the fibres in cecum and colon that are important for the size of methane production," Anne Louise F. Hellwing explains.

The new project will be subject to the following two attempts:

1. Laboratory experiments at the Norwegian University of Life Sciences – NMBU

This first study aims to test degradation and gas development from various feed materials in laboratory experiments (in-vitro experiments). An in-vitro experiment attempts to simulate the entire or part of an animal's digestive tract and the digestion of a feedstuff. The results of the in-vitro experiment will form the basis for the selection of feedstuff that will be used for the subsequent test on horses.

2. Test on horses at Aarhus University 

The purpose of this second study is to measure methane production from horses fed with two different feed rations selected on the basis of the results of the in-vitro experiment. Four horses will be used in the experiment. The study contains two periods of approximately three weeks’ duration. In each period, the horses are first accustomed to the rations over three weeks and feed intake is measured. Subsequently, the animals’ CO₂ and methane excretion and oxygen uptake are measured for three days. This takes place in the respiratory chambers at AU Viborg - Research Centre Foulum's experimental stables.

Based on the measurements in the experiments and literature values, feeding plans will be prepared with different coarse feed rations and, if necessary, supplementary feed in collaboration with SEGES. "With the new feeding plans, we expect to be able to illustrate how it is possible in practice to feed horses more climate-friendly," Anne Louise F. Hellwing concludes.

Supplementary information
We strive to ensure that all of our articles comply with Universities Denmark’s Principles for good research communication. Therefore, we have supplemented the article with the following information:
Funding	Grant from Hesteafgiftsfonden
Collaborators	Rasmus Bovbjerg Jensen, Norwegian University of Life Sciences Jørgen Kold, Seges Innovation
External comments	No
Contact	Anne Louise Frydendahl Hellwing e-mail: annelouise.hellwing@anis.au.dk Telephone: 87157903