No clear link found between cattle deaths and Bovaer feed additive

Researchers at Aarhus University have concluded there is no evident connection between the feed additive Bovaer and reports of reduced milk production or increased cattle mortality, following a three-month study of 73 Danish dairy herds, DR reports.

The investigation, commissioned by the Danish Agri-Fish Agency, analysed production, health, and mortality data from farms already using Bovaer—a methane-reducing supplement designed to cut livestock emissions by inhibiting enzymes in cows’ stomachs. According to Niels Bastian Kristensen, associate professor at the university’s Department of Animal and Veterinary Sciences, the findings showed “no clear overall pattern” linking Bovaer to the reported issues.

“Our analysis does not necessarily capture every challenge farmers may have experienced,” Kristensen acknowledged, noting that individual herds could still face problems. The study did not track cows before, during, and after Bovaer’s introduction, a limitation highlighted by industry groups.

Kjartan Poulsen, chair of the Danish Dairy Producers Association, previously told DR that farmers observed illness and lower milk yields in cows after feeding them Bovaer. The trade organisation Landbrug & Fødevarer has called for further controlled trials to examine the additive’s effects more thoroughly, including pre- and post-administration monitoring.

Bovaer, which contains the active compound 3-nitrooxypropanol (3-NOP), is one of two approved methane-reducing feed options mandated for conventional Danish dairy farms with over 50 cows starting in 2025. While not obligatory for organic producers, the additive is estimated to cut methane emissions by 27% if used as directed—requiring at least 80 days of annual feeding to meet an 8% reduction target.

Food Minister Jacob Jensen has previously stated that Bovaer is approved across the EU without reported issues, though farmers concerned about its use may delay implementation until autumn 2026.