Sustainability & efficiency

How does use of the methane mitigating feed additive Bovaer affect animal variance and ranking of methane and yield traits in dairy cattle?

---

Abstract

Breeding for reduced enteric methane emissions has gained traction as a climate mitigation strategy, while nutritionists have explored feed additives such as Bovaer to reduce emissions and potentially improve efficiency, given that methane represents an energy loss in dairy cows. Since May 2025, official methane breeding values have been published in Denmark via Nordic Cattle Genetic Evaluation. Concurrently, Danish legislation mandates that conventional dairy farmers supplement 60 mg Bovaer/kg dry matter for 80 days annually. This introduces a potential genotype-by-environment (G×E) scenario, where genetic predisposition interacts with feed-based mitigation-yet this interaction remains unexplored in commercial settings. This study investigated whether Bovaer supplementation affects trait variance and animal ranking for methane and milk production traits. Preliminary data were collected from two commercial Jersey herds (546 cows) supplementing Bovaer ("treatment group") and two Jersey herds (574 cows) without supplementation ("reference group"), spanning November 2024 to July 2025. One of the treatment herds began methane data collection in February 2025. We defined three periods: pre-Bovaer (November 2024-January 2025), Bovaer (February-April 2025), and post-Bovaer (May-July 2025). Gas data were obtained as weekly averages of CH₄ and CO₂ concentrations (ppm) from Guardian sniffers installed in milking robots. Milk yield, fat%, and protein% were sourced from monthly test-day records and used to calculate energy-corrected milk (ECM). A three-trait model was applied for each phenotype of interest across periods using the DMU software, including fixed effects (parity, herd×parity×weeks in milk, herd×year×month), random cow effects (no pedigree), and residuals. Bovaer supplementation reduced mean CH₄ ppm and CH₄/CO₂ ratio by 32% and 25% compared to the pre-Bovaer period, and by 10% and 19% compared to the post-Bovaer period, respectively. Interestingly, fat% increased during Bovaer supplementation by 3% and 7% compared to the pre- and post-supplementation periods, respectively. Repeatability of CH₄ ppm and CH₄/CO₂ ratio decreased in the treatment group during Bovaer supplementation, suggesting increased environmental influence. However, correlations between periods for CH₄ ppm and CH₄/CO₂ ratio remained relatively stable compared to the reference group, indicating limited reranking among individuals. For fat%, the lowest correlation (0.79) was observed between the pre-Bovaer and Bovaer periods in the treatment group, compared to 0.92 in the reference group, suggesting some degree of G×E. In conclusion, Bovaer reduces CH₄ ppm and CH₄/CO₂ ratio and may increase milk fat content. While repeatability of methane traits declines during supplementation, reranking appears minimal, suggesting limited G×E. Further analyses incorporating pedigree-based relationships and expanded datasets later in 2026 will help clarify the genetic implications of Bovaer use in methane mitigation strategies.

Keywords: 2026

How to Cite:

Bjerring, M., Lassen, J., Løvendahl, P., Lund, M., Stephansen, R. & Villumsen, T., (2026) “How does use of the methane mitigating feed additive Bovaer affect animal variance and ranking of methane and yield traits in dairy cattle?”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2283088. doi: https://doi.org/10.31274/wcgalp.23479

Rights: 1