Grass and grazing have the potential to reduce not only ammonia emissions, but also methane emissions. This is evident from a long-term grazing trial that Wageningen Livestock Research started in 2020. The first results of 2021 are now known. They again show that methane emissions are lowest especially in the spring with full grazing, compared with grass silage and zero-grazing.
Fresh grass as a base
With grassland use, dairy farmers can control both ammonia emissions and enteric methane emissions from dairy cows. Enteric methane is produced by fermentation in the rumen of dairy cows. Grassland forms the basis of dairy farming and grass products are an important part of the ration; that is why Wageningen Livestock Research (WLR) started a grazing trial at the Dairy Campus innovation center in Leeuwarden in 2020.
In two trials of three periods each (spring, summer, autumn), WLR compares the methane emissions of dairy cows on a ration consisting of full grass silage, full fresh grass in the barn (summer zero-grazing) and full grazing. In addition, the researchers distinguish between short and long grass when grazing during the day, with grass silage in the barn at night.
Lowest methane emissions in spring with grazing
The results of the first year of grazing research already showed that 'grass and grazing' have the potential to reduce not only ammonia emissions, but also methane emissions. In the spring of both 2020 and 2021, methane emissions were clearly lowest with full grazing. The first results of 2021 are therefore comparable to the results of the previous year.
In 2020, the emission was also lower in the summer and autumn than with grass silage and summer zero-feeding. The following year, this difference was not demonstrated during these periods. The differences in methane emissions between limited grazing on short and long grass were also investigated. In 2020, methane emissions were lower in cows that grazed on short-growth grass. In 2021, emissions also seemed lower on short grass, but the differences were very small (not demonstrable).
Translation into practice
The report with the results for 2021 will be published at the end of 2022. This year, the cows also grazed outside on the Dairy Campus until mid-October, which means that the 2022 trial has been completed. For a proper translation into practice, WLR in 2022, in addition to full grazing, also investigated methane emissions from cows that were given limited grazing and limited summer feeding and additionally fed grass silage. In addition, this year the effect of narrow plantain on enteric methane emission during full grazing was investigated.