Healthier livestock can lower emissions per unit of food, but total emissions may still rise

When a dairy cow miscarries, the feed, land, water and greenhouse gases invested during pregnancy yield no milk, calf or income. Methane produced by microbes in the cow's stomach during digestion is the main livestock greenhouse gas, and healthier animals emit less methane per liter of milk or kilogram of meat because they are more productive.

A peer-reviewed study reviewing evidence from livestock systems worldwide found that preventing disease improves growth, milk yield, fertility and survival, often lowering emissions intensity. However, the authors say current evidence is not yet strong or consistent enough for animal health to be confidently included in climate policy, because studies use different assumptions and estimates rather than direct measurements.

Building on work supported by the Global Methane Hub, the researchers launched Halow (Health Approaches for Lowering Livestock Emissions), recently approved as a major initiative of the Global Research Alliance on Agricultural Greenhouse Gases. Halow will compare health interventions across farming systems to evaluate which reduce total emissions or only emissions per unit of food, at what cost, and who benefits.

Modeled data from farms in northern Tanzania showed that cattle miscarriage increased emissions per kilogram of milk by 4% in indigenous cattle and 15% in higher-yielding cattle. Combined cattle and goat losses equated to the annual animal protein consumption of about 649,000 Tanzanians.

In western Kenya, 16% of local beef calves died in their first year, mostly from infection. The protein lost equaled the annual beef protein consumption of roughly 4.5 million Kenyans. Halving mortality to 8% cut estimated enteric methane per kilogram of beef by 3.2%, but total herd methane rose because more surviving animals produced more beef.

The researchers stress this is not an argument for allowing calves to die, but for measuring food security, livelihoods and climate outcomes together. Improved efficiency does not guarantee an absolute reduction in greenhouse gases from livestock.

Current national inventories estimate livestock emissions from animal numbers and standardized figures, which may not capture how better health changes yields, growth, fertility, mortality and replacement needs. Halow aims to provide a platform for comparing interventions and recognizing that negative results matter too.

Animal health alone will not solve the livestock sector's climate impact. The authors argue a fair transition requires reducing excess consumption where it is high, improving access to nutritious food where it is low, and cutting avoidable losses everywhere.