Acetonaemia (ketosis) occurs when dairy cows mobilise body fat faster than they can metabolise it in early lactation, causing neurological signs, reduced production, and significant welfare harm in high-yielding herds.
Ketosis illustrates how production pressure and animal welfare interact in high-yielding dairy systems. Modern dairy breeds have been selected for milk production that outstrips their metabolic capacity in early lactation — the energy demand of peak milk production exceeds what most cows can consume even with unlimited access to high-quality feed. The resulting negative energy balance drives fat mobilisation, and in cows that enter the dry period with excessive body condition, the fat mobilisation rate overwhelms hepatic capacity. Clinical ketosis causes genuine neurological suffering: affected cows are incoordinated, exhibit abnormal repetitive licking or chewing behaviour, and are profoundly depressed and anorexic. Subclinical ketosis, affecting far more animals, causes subtle discomfort, reduced immune competence, and predisposes to a cascade of secondary diseases in the month after calving. Prevention through transition nutrition management — avoiding overconditioned cows at drying off, providing appropriate transition diets — is more welfare-effective and economically efficient than treatment of established disease.