The average dairy cow in the UK and US is culled at 5-6 years of age, a fraction of her 20-year natural lifespan. The reasons for early culling — mastitis, lameness, reproductive failure, and declining yield — are intimately linked to the welfare costs of high-yield production.
The short productive life of the modern dairy cow is a direct consequence of the metabolic demands placed upon her by selection for extreme milk yield. A high-yielding dairy cow enters a state of severe negative energy balance immediately after calving, mobilising body reserves to sustain milk production at rates her metabolism cannot easily support. This negative energy balance drives metabolic diseases, immune suppression, lameness, and reproductive dysfunction that collectively shorten her productive life. The welfare implication is clear: a system that burns through individual animals in 5-6 years, when they are biologically capable of living 20, is generating enormous cumulative suffering. Herd longevity is a meaningful welfare metric, and consumer choices and certification schemes that reward it create incentives for genuinely healthier animals.