A new study published by Aarhus University has found no overall evidence linking the methane-reducing feed additive Bovaer to increased cow mortality, reduced milk production, or higher disease incidence across Danish dairy herds.
The research was commissioned by the Danish Food, Agriculture and Fisheries Agency in October 2025 following reports from some dairy farmers who claimed their herds experienced health issues and declining milk yields after the introduction of Bovaer into feeding programs.
The study analysed production and health data from 73 Danish dairy herds comprising approximately 27,650 cows that used Bovaer during 2025.
According to the researchers, the data showed no overall negative impact on:
- milk yield
- disease occurrence
- mortality rates
- mastitis incidence
- metabolic disorders
during periods when Bovaer was included in feed rations.
Bovaer contains the active ingredient 3-nitrooxypropanol (3-NOP), a methane-reducing compound designed to inhibit methane formation in the rumen. The additive has been approved for use in the European Union following safety and efficacy assessments conducted by the European Food Safety Authority.
The additive has become central to Denmark’s national methane-reduction strategy for dairy farming. Since January 1, 2025, conventional dairy farms in Denmark with more than 50 cows have been required to reduce methane emissions either by increasing dietary fat content year-round or by incorporating Bovaer into feed for at least 80 days annually.
Niels Bastian Kristensen, Associate Professor at the Department of Animal and Veterinary Sciences at Aarhus University, said the available data did not indicate any broad negative production or health effects associated with Bovaer use.
However, the researchers stressed that important limitations remain and acknowledged that some farmers have reported significant operational challenges following adoption of the additive.
“It is important to emphasise that there is great variation between herds, and that the study does not necessarily capture all the challenges that dairy farmers have experienced in practice,” Kristensen said.
The researchers further noted that some health or welfare-related issues may not have been fully reflected in official records. Cows experiencing reduced feed intake, stress, or lower well-being may not always receive prescription treatment and therefore may not appear clearly in disease or medication datasets used in the analysis.
The findings are expected to contribute to ongoing debate across Europe regarding the commercial implementation of methane-reduction technologies in livestock production, particularly as regulators and dairy companies intensify pressure to lower agricultural greenhouse gas emissions without compromising animal health or farm productivity.
