A three-year trial of 15 farms has concluded that more than half (57%) of dairy cows are experiencing hypocalcemia (milk fever) post calving.

A large proportion of the cases were found to be sub-clinical, meaning that the disease would go undetected without blood sampling.

Clinical milk fever can occur at calving when a cow is unable to mobilise enough calcium to meet increased demand for milk production. This can result in ‘downer cows’ that may struggle to recover.

Sub-clinical disease also causes immunosuppression and can lead to increased risk of ‘whites’ and displaced abomasums post-calving.

“Sub-clinical milk fever is highly prevalent”

James Husband, vet consultant, EBVC

See also: Milk fever prevention: Best practice guide and case study

Vet consultant James Husband from EBVC, who carried out trial said, “Sub-clinical milk fever is highly prevalent and the only way to know if it’s occurring is to blood sample fresh calved cows.

“If blood calcium levels are below 2mmol/litre in the first 24 hours after calving, then sub-clinical milk fever is occurring.”

A significant contributory factor to sub-clinical milk fever is the forage used in dry cow diets, which may lead to high levels of calcium and potassium.

In the farm trial, it was found that half of dry cow rations had higher than recommended levels of potassium and a third of TMR samples had dietary calcium levels of over 0.9%.

The study concludes that all dairy farmers could benefit from regularly testing transition cow diets for macro-minerals and monitoring fresh cow blood calcium levels as part of their milk fever prevention strategy.

For best practice on testing blood calcium levels, forages and TMRs and a case study on successfully controlling milk fever see the best practice guide and case study on milk fever prevention.