When a dairy cow miscarries, a farmer loses far more than an unborn calf. Feed has been grown, land and water used, and greenhouse gas released during the cow’s pregnancy but milk production, a future animal and income will be lost.

One of the most important of these greenhouse gases is methane. Methane is produced by microbes within a cow’s stomach during digestion (known as enteric-methane) and most of it is breathed out into the atmosphere. Instead, healthier animals are more productive, so the amount of methane they emit is associated with more milk or meat, reducing the emissions associated with each litre or kilogram produced.

My research focuses on diseases in farm animals such as cows, goats and sheep. In a recent peer-reviewed journal paper, my team and I examined evidence from livestock systems around the world. We found that preventing disease can improve growth, milk production, fertility and survival, often lowering the emissions associated with each litre of milk or kilogram of meat. However, the available evidence is not yet strong or consistent enough for animal health to be included confidently in climate policy.

Studies investigating greenhouse gas emissions in livestock make different assumptions and usually use estimations rather than........

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