Milk fever (hypocalcaemia) occurs around calving time, when the calcium level in the blood falls below the required threshold.
Around parturition, calcium requirements dramatically rise due to increased foetal growth, contractions during labour and a massive demand for colostrum production.
The cow’s ability to mobilise calcium from bones is exceeded, so the animal becomes deficient.
There are many predisposing factors, including breed, age and the transition diet. Jersey cattle have a lower amount of vitamin D receptors than Holsteins, which means they can absorb less calcium from the intestine. As cattle get older, their milk production increases and so their demand for calcium is greater. Cows with a body condition of more than four and cows carrying twins are also more susceptible.
Symptoms most commonly appear 24 hours after parturition and in stages, depending on severity.
Treatment options vary depending on what stage of the disease the cow presents. Oral treatments are available for the early stages, but cows in stage two or three often require intravenous calcium, with the standard treatment being 400ml of 40% calcium borogluconate administered slowly and warmed to body temperature.
To reduce the incidence, the dry cow diet should be closely monitored, along with body condition around calving. It may be worth bolusing high-risk cows at the time of calving.
It is important to remember some of the herd may also be suffering from subclinical milk fever, leaving them at much higher risk of other metabolic diseases and retained foetal membranes.
If you are seeing a high incidence of milk fever or metabolic diseases, speak to your vet and nutritionist.
*Jessica Warwick is a veterinary surgeon at Lisnafillin farm vets in Ballymena.