Dutch Dairy Farmers Can Cut Nitrogen Emissions Without Reducing Milk Production

2026-03-17 green

Wageningen, Tuesday, 17 March 2026.
Groundbreaking research from Wageningen University reveals dairy farmers can slash nitrogen emissions by feeding cows 12% less protein while maintaining milk output. The multi-year study of 64 cows shows reducing protein from standard Dutch levels cuts harmful urine nitrogen by nearly 40 grams daily without affecting methane emissions per kilogram of milk produced.

Research Methodology and Scale

The comprehensive study, funded by the Vereniging Diervoederonderzoek Nederland (VDN), LVVN, and het Melkveefonds, monitored 64 dairy cows through two complete lactation periods of at least 44 weeks each [1]. Researchers at Wageningen University & Research divided the animals into three groups receiving feed with varying protein levels: 133, 143, and 154 grams of raw protein per kilogram of dry matter [1]. These protein levels all fell below the current Dutch practice average of 161 grams per kilogram of dry matter [1]. Throughout the study period, scientists continuously measured feed intake, milk production, and methane emissions while collecting manure and urine samples at the beginning and middle of lactation periods to create a complete picture of nitrogen excretion [3].

Dramatic Nitrogen Reduction Results

The study revealed striking differences in nitrogen handling between protein groups during the first lactation period. Cows on the low-protein diet consumed 462 grams of nitrogen daily, compared to 548 grams for medium-protein and 590 grams for high-protein groups [1]. More significantly, urine nitrogen excretion dropped dramatically as protein levels decreased, measuring 105 grams daily for low-protein cows versus 146 grams for medium-protein and 185 grams for high-protein animals [1]. The reduction from high to medium protein levels represents a decrease of 21.081 percent in urine nitrogen excretion. The low-protein group achieved the highest nitrogen utilization efficiency for milk production at 34.8 percent, compared to 31.9 percent for the high-protein group [1].

Production Impact Analysis

Critical to the research findings was determining whether protein reduction affected milk output and animal performance. The study demonstrated that reducing crude protein from 154 to 143 grams per kilogram of dry matter does not significantly affect milk production or feed intake [1]. However, further reduction to 133 grams per kilogram resulted in decreased feed intake and milk production [1][5]. This finding provides dairy farmers with a clear operational threshold: protein levels can be reduced to 143 grams per kilogram without compromising productivity, offering what researchers describe as “prospects for more sustainable dairy farming” [1].

Methane Emissions Remain Stable

Addressing concerns about potential climate trade-offs, the research found that total methane excretion actually decreased in the low-protein group to 442 grams daily, compared to 484 and 488 grams daily for medium and high-protein groups respectively during the first lactation [1]. Importantly, methane production per unit of milk or feed remained comparable across all protein levels [5]. The study concluded that lowering protein content leads to clear decreases in nitrogen excretion, especially through urine, “without increasing methane emissions per kilogram of milk” [1]. This finding contradicts initial concerns that reducing protein might create new climate disadvantages, instead showing that environmental benefits can be achieved without introducing additional greenhouse gas emissions [1][5].

Bronnen

emission reduction livestock nutrition