Methane emission in cattle strongly depends on the quality and proportion of grass herbage, grass silage and maize silage. Grass harvested at an earlier stage of maturity, decreases methane emission substantially, maize silage results in a lower methane emission than grass silage, and the most recent investigation indicates that advancing maize harvest maturity reduces methane production in dairy cattle. These are three practical measures that farmers can use in farm management. PhD research at the Center of Animal Nutrition of Wageningen UR, as part of the innovation program Low Emission Animal Feed, establishes for the first time a clear relationship that can be used by the dairy sector.
In dairy farming, methane contributes most to the global warming impact of milk production. The agricultural stakeholders and the Dutch government signed a covenant to reduce greenhouse gas emission by 30% in 2020 compared to 1990 levels. Therefore, the former Dutch Dairy Board, the Product Board Animal Feed and the Dutch Ministry of Economic Affairs funded the innovation program Low Emission Animal Feed. In this program, researchers accurately measure the effect of feed composition on methane emissions in dairy cattle in respiration chambers of Wageningen University. Results from this research program are exchanged with other national projects including ‘Cows & Opportunities’ and projects aimed at the development of management tools including the ‘Carbon Feed Print’ and ‘Annual Nutrient Cycle Assessment’ tools. In this way, scientists help to reduce the contribution of the dairy sector to climate change.
Previous research of Wageningen UR showed that grass quality has a large effect on methane emission. On a grass-based diet, early-cut and high fertilized grass reduces methane emission per kg fat- and protein-corrected milk by up to 30%. Maize silage is the second most important forage after grass and grass silage, and maize silage comprises about a quarter of the average Dutch dairy diet. Compared to an average grass silage, maize silage decreases methane emission by more than 10%.
Recent research findings indicate, for the first time for dairy cattle, that advancing maize harvest maturity further reduces methane emissions. Worldwide it is generally assumed that methane emission does not vary much with roughage quality. The research of Wageningen UR has been conducted in a systematic manner and using accurate measuring techniques, and this allowed clear relationships between forage quality and methane production to be established. As the maturity of maize silage at harvest advances, the dry matter content increases. The recent findings indicate that per percent increase of dry matter content, methane emission per unit milk is 1.5% lower. This reduction is related to an increased starch content and a reduced starch degradability in the rumen. An increase of the dry matter content of 5% due to advanced maturity of maize at harvest results in an 8% decrease in methane emission.
The various options related to roughage production (grassland management, harvesting moment of maize, dietary proportion of maize silage) allow for a substantial reduction in methane emission. The magnitude of this reduction on a specific dairy farm depends on the feasibility to implement these measures, including conditions on derogation and manure application as part of current manure legislation. The research in Low Emission Animal Feed was conducted by PhD research workers Bayissa Hatew, Geronda Klop, Sabrina Podesta, and Daniel Warner.