Enterische methaanemissie van melkvee in relatie tot (vers) graskwaliteit: Rapport jaar 3 en 4: 2022 + 2023 : Resultaten van een meerjarige beweidingsproef naar methaanemissie bij onbeperkte weidegang, beperkte weidegang en beperkte zomerstalvoedering

Samenvatting

The goal of this multiannual research was to quantify the enteric methane (CH4) emission of dairy cattle receiving fresh grass diets. In two consecutive years (2022 and 2023) containing three periods per year (April/May, June/July and August/September) the same experiment has been performed were enteric CH4 of dairy cows was measured during unrestricted grazing, restricted grazing and restricted zero-grazing. The results found in this two-year study are in comparison with the previous two-year study (2020 and 2021), showing the lowest CH4 emission on unrestricted grazing. Overall, regardless of year or period, the average CH4 yield of cows during unrestricted grazing was 15.7 g CH4/kg dry matter (DM), restricted grazing 18.9 g CH4/kg DM and restricted zero-grazing 21.1 g CH4/kg DM. The CH4 yield of fresh grass differed between periods, with a lower yield in spring. No effect of year was found. In this two-year study the effect of fresh grass seemed dependent on the amount of grass silage in the diet. The CH4 emission during grazing was lower than the emission factor used in the current national emission models, which shows the importance of adjusting the emission factor of fresh grass based on grass quality and diet composition.