Ketosis (hyperketonaemia) is one of the most economically and welfare-significant transition cow diseases in dairy herds. Subclinical ketosis affects up to 40% of dairy cows in the first two weeks after calving and is associated with reduced milk production, impaired fertility, increased disease susceptibility, and elevated culling risk. Proactive management substantially improves individual and herd welfare.
Pathophysiology
In early lactation, energy demands of milk production often exceed dietary energy intake, creating negative energy balance (NEB). The body mobilises fat reserves (body condition), generating non-esterified fatty acids (NEFAs). The liver converts NEFAs to ketone bodies (beta-hydroxybutyrate, BHB; acetone; acetoacetate) — useful energy substrates but harmful at elevated concentrations. Cows with excessive BCS at calving (>3.5 in UK scale) mobilise more fat and are at highest risk.
Clinical vs Subclinical Ketosis
- Subclinical ketosis: Blood BHB 1.2–2.9 mmol/L; no obvious clinical signs but measurable production losses and disease risk
- Clinical ketosis: Blood BHB ≥3.0 mmol/L; signs include reduced appetite, dropping milk yield, lethargy, acetone smell on breath, and sometimes neurological signs (nervous ketosis)
Detection and Monitoring
Cow-side blood ketone testing using handheld meters (e.g., Precision Xtra) is the gold standard — test all cows at days 3–5 and 7–10 post-calving. Milk ketone strips and inline milk sensors (NEFA, BHB detection) offer herd-level monitoring. Urine acetone strips are less sensitive for subclinical ketosis. Herd-level prevalence above 15% indicates a management problem requiring investigation.
Treatment
Propylene glycol (PG): Oral drench of 250–500ml twice daily for 3–5 days; the most evidence-based treatment. PG is a gluconeogenic precursor that bypasses the metabolic block.
IV glucose: 400ml of 50% dextrose for severe clinical cases; provides rapid glucose but short-term — follow with PG.
Corticosteroids: Dexamethasone stimulates gluconeogenesis but has immunosuppressive effects and has limited evidence basis for routine use.
Vitamin B12: Supports liver function and gluconeogenesis in cobalt-deficient herds.
Prevention Strategies
- Avoid over-conditioning cows at drying off (target BCS 2.75–3.0)
- Adequate dry matter intake in the close-up dry period (−3 weeks to calving)
- Negative dietary cation-anion balance (DCAB) diets or controlled energy (straw-based rations) in close-up period
- Minimise pre-calving pen moves and social disruption
- Ensure adequate feed space (1 cow: 1 feed space minimum) in transition pen
Welfare Significance
Subclinical ketosis causes chronic malaise, reduces immune function (predisposing to mastitis, metritis, and other diseases), impairs fertility (delayed first ovulation), and increases first-lactation culling risk. Effective prevention is both an economic and ethical imperative. Routine monitoring and prompt treatment are hallmarks of high-welfare dairy management.