Out of the total methane emission of a dairy farm, about 58% comes directly from the cows, the remaining 45% results from farm operations. The 58% methane emission coming from dairy cows is split into 42% coming from enteric methane production and 16% coming from manure (see figure 1). This means that 72% of the methane emission that is directly related to cows is coming from enteric methane production and 28% is coming from manure.

One way to reduce methane emission of dairy cattle is to reduce the amount of methane per kg of milk produced by increasing the efficacy of dairy production:

• If dairy cows calve at an earlier age, they produce less methane up to the moment they start producing milk. Research by the ILVO1 showed methane emission of dairy cows per litre of milk produced is reduced by 3.1% if the age at first calving the dairy herd is being reduced by 2 months.
• Dairy cows produce a fixed level of methane to produce energy for maintenance, regardless of their production level. If the milk production per lactation goes up, this methane produced for maintanance is “diluted” over more kilogram of milk. Increasing the milk production per day by 3 kg will reduce methane emission of dairy cows per kilogram of milk produced by up to 8.4%1.
• If the number of lactations per cow goes up, a similar effect occurs; methane produced during the rearing phase is “diluted” over more lactations. If next to increasing the production by 3 kg per day, the culling rate is reduced by 5%, methane emission per litre of milk produced will be reduced by 11.7%1.
• If dairy cows are not healthy, feed efficiency is being reduced, because the immune system of dairy cows uses a lot of energy which as a consequence cannot be used for milk production. It is estimated that 30% of the production potential of dairy cows is waisted because of health issues. This means that healthier cows produce less methane per litre of milk produced.

The age at first calving can be reduced by an intensive rearing programme with high levels of milk feeding during the first 12 weeks of a calf’s life. It has been shown that such an intensive rearing programme also increases the milk production per lactation and the number of lactations per cow2.

A good transition management programme for dairy cows will lead to a further increase of milk production per lactation and number of lactations per cow. As most of the health problems of dairy cows are related to poor transition, a good transition programme will also improve health and thus feed efficiency of dairy cows.

Lastly, there is the option to reduce the methane emission from manure. Cows produce manure and urine separately, but once the 2 are mixed in the manure pit, a chemical reaction starts that results in the production of methane from slurry. One way to reduce the problem of methane production in manue is to keep urine and manure as much as possible separated from each other. Manure additives that can reduce the emission of methane from manure are under development.

1. Data from the ILVO, Flanders Research Institute for Agriculture, Fisheries and Food.
2. Leal, L, (2019). Lifetime impact of early life planes of nutrition in dairy calves, Proceedings of Smart Calf Rearing Conference, University of Guelph, Canada, November 2-5.
3. Miller, M.D, Lanier, J.S, Kvidera, S.K, Dann, H.M, Ballard, C.S. and R.J. Grant (2020). Evaluation of source of corn silage and trace minerals on lactational performance and total-tract nutrient digestibility in Holstein cows. J. Dairy Sci., 103:3147-3160.
4. Guimaraes, O, Jalali, S, Wagner, T, Spears, J and T. Engle (2019). The influence of trace mineral source on fiber digestion, rumen fermentation characteristics, and mineral solubility in beef cattle fed a low-quality forage diet. J. An. Science. 97, Issue Supp. 3: 167.
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8. Van Kuijk, S, Swiegers, P and Y. Han (2022), Hydroxychloride trace minerals improve apparent total tract nutrient digestibility in Bonsmara beef cattle. Livestock Science: 256(4):104820.
9. Ibraheem, M, Kvidera, S. and B. Bradford (2021). Meta-analysis to determine the impact of trace mineral source on nutrient digestibility in dairy and beef animals. J. Dairy Sci. 104:97.
10. Oba, M. and M.S. Allen (1999). Evaluation of the Importance of the Digestibility of Neutral Detergent Fiber from Forage: Effects on Dry Matter Intake and Milk Yield of Dairy Cows. J. Dairy Sci., 99:589-596.
11. Yasui, T, Ryan, C.M, Gilbert, R.O, Perryman, K.R. and T. R. Overton (2014). Effects of hydroxy trace minerals on oxidative metabolism, cytological endometritis, and performance of transition dairy cows. J. Dairy Sci. 97: 3728-3738.
12. Daniel, J.B, Kvidera, S.K. and J. Martín-Tereso (2020). Total-tract digestibility and milk productivity of dairy cows as affected by trace mineral sources. J. Dairy Sci. 103 (10).