Taking a proactive approach to milk fever prevention will avoid a disease that is often viewed by milk producers as a common risk associated with calving dairy cows, according to David Black, a vet at Paragon Veterinary Group in Cumbria and managing director of XLVets.
“Milk fever tends to be under the radar of many dairy farmers. It is something they do not tend to discuss with their vet because they easily recognise the symptoms and know how to treat it. But the disease has a very important economic impact in the dairy herd—and for every case a farmer sees there will be a number of subclinical cases that go unnoticed.”
Between fi ve and 10% of UK dairy cows go down with clinical milk fever each year. But up to 39% of the milking herd is estimated to suffer from sub-clinical milk fever or hypocalcemia following calving.
The knock-on effects include retained cleansings, metritis and impaired fertility. “And the muscles in the teat end of a cow going down with milk fever are relaxed which leave the cow prone to mastitis, and subsequent higher cell counts” he warns. The economic cost of a case of clinical milk fever is estimated to be between £200 and £250 per cow.
Mr Black is advocating the use of the calcium bolus Bovikalc to reduce the risk of the disease. The bolus is produced by Boehringer Ingelheim which has just taken the marketing of the product inhouse.
He recommends that it is used routinely with cows calving for the third time or more and for cows which have had previous cases of milk fever. He also suggests that if a cow goes down with milk fever that it is treated with an intravenous solution of calcium followed up with calcium boluses.
“There is good science behind the product which contains calcium chloride and calcium sulphate which help reduce the risk of milk fever in three ways,” he explains. “The bolus dissolves rapidly in the rumen and the calcium chloride provides an immediate source of calcium. The calcium sulphate is broken down by rumen bugs and provides a slow release supply of calcium.
“In addition the chloride helps to reduce the pH of the cow’s urine which assists the cow in mobilising her own calcium reserves. “Milk contains about 1.1 grams of calcium per kilogramme of milk,” says Mr Black. “Colostrum contains between 1.7g and 2.3g per kilogramme of milk so the production of colostrum is a driver for milk fever.
“When a cow calves her calcium requirement increases by around 70g-80g a day. A bottle of 40% calcium solution will provide 12g of calcium while a Bovikalc bolus provides 42g. The bolus is easier to administer than injecting calcium from a bottle and reduces the associated risk of abscess and infection caused by a needle.”
Some milk producers use full or partial DCAB (Dietary Cation-Anion Balancing) rations to reduce milk fever. However, the anionic salts added to the diet tend to be unpalatable and reduce dry matter intakes during the dry period, and in an ideal situation, DCAB should only be used for the last 10 days of transition, which is diffi cult on many UK farms. Nor is DCAB suitable for heifers. “The heifer’s skeleton is still not mature and it is not ideal for them to draw calcium from bone reserves,” he says.
Paragon is currently conducting trials to investigate reducing the risk of milk fever. The theory is that if a cow’s urine pH is more than 8.25 twenty-four hours before calving then it will be prone to milk fever and administering Bovikalc calcium boluses can reduce this risk. “The trials are ongoing and we are getting more information. If the study proves successful then we may be able to reduce the reliance on DCAB diets and use urine pH as an indicator of the higher risk cows which would benefi t from bolusing,” says Mr Black.
“The boluses cost less than £6.00 each. But with each clinical case of milk fever costing up to £250 they are very cost effective,” he adds.