Submitted by Dr. Christine Ewert Hill D.V.M.
Head for the Hills Veterinary Health Services
Redvers and CarlyleHealth Services
The name "milk fever" is very misleading, because a cow with milk fever, does not actually get a fever! Not to be confused with mastitis (udder infection), milk fever is an imbalance of calcium and sometimes magnesium in the cow's body. Milk fever is often seen in older cows, 2nd calf heifers, high milk producing females, cows carrying twins, or in cows with a substandard content of calcium in their diet.
The most significant sign of milk fever is a "downer cow" usually within 72 hours of calving. That is a time when the cow begins to milk very heavily, causing a drastic strain on her calcium stores. Calcium plays a large role in smooth muscle function; therefore, the rumen will not be as active, pupils will be slow to constrict in response to light, the bladder may not be expressing urine. One of the biggest dangers with milk fever is the effect of a lack of calcium on the heart. The heart may beat weakly.
The best way to prevent milk fever, is to provide an appropriate amount of calcium, magnesium, phosphorus, and vitamin D in the diet. Good quality alfalfa hay can be very helpful to provide good minerals. Hay can be analyzed to assess its quality. Feeding oat straw without mineral supplementation or hay can predispose cows to milk fever. A 2:1 mineral can be helpful, especially nearing parturition. Vitamin D injections enable cows to access the calcium in their diet. If you have a cow that you know milks very heavily, she can be given calcium in a paste form for a few days following calving.
Once a cow is down with milk fever, the veterinarian may do some blood tests to assess if calcium is low or if magnesium, and phosphorus are imbalanced. Treatment may include intravenous or subcutaneous injections of calcium. Often the injections also have dextrose for energy, and magnesium and phosphorus. If a magnesium shortage is suspected, oral magnesium may also be given.
If the cow is treated early enough, the recovery can be very fast, and her prognosis is good. Often the cow may try to stand before all of the medication has been given! Usually one can hear the cow's rumen start to move again, improved gut sounds, and she may urinate as her bladder tone improves. Her heart will begin to beat stronger. However, if the cow is not treated soon enough or if she has a very severe lack of calcium, then her prognosis may be poorer, as permanent muscle damage can occur, if the cow is down too long. Occasionally the cow may even have a heart attack during treatment with calcium because of the severe calcium imbalance for too long prior to treatment.
Having a cow in good body condition and on a good diet with mineral supplementation will help prevent milk fever. Noticing a high producing cow go down, and getting her veterinary care quickly can mean a promising survival rate.
