Milk fever is a condition caused by low blood calcium levels (hypocalcaemia) in cows. During the final months of pregnancy and early lactation, there is a considerable drain on a cow’s blood calcium levels to supply the developing calf and to build up milk for lactation. If this drain occurs too quickly, the amount of calcium in the blood may fall below optimal levels resulting in milk fever.


Who is most likely to be affected?
Older, high producing cows in good body condition score, shortly before or after calving. Occasionally it can occur a few weeks after calving when cows are in oestrous or they are stressed.



The clinical signs of milk fever can be classified into three stages.

Stage 1 - Cow may appear excited with stiffening of the muscles and trembling (may go unnoticed)

  • Reluctance to move or eat; hind limbs may become stiff and the animal may stagger

Stage 2 - Cow will be found lying or sitting down and cannot get up; often has a ‘kink’ in her neck or her head folded along her flank

  • Dull, cold to touch, low body temp., heavy breathing, increased heart rate

Stage 3 - Cows are often unresponsive and almost in an unconscious state

  • The animal will lay on her side with legs stretched out; bloat often develops and regurgitation is likely
  • Most animals will die if left untreated in this stage



Ensure the animal is sitting up to reduce the danger of choking. Try prop her up with a bale of hay or a fence post if required. Animals with milk fever need an injection of calcium (Calcigol plus or Minbal 4 in 1 – calcium borogluconate, magnesium, phosphorus and glucose) under the skin and behind the shoulder (or on the neck just in front of the shoulder), as early as possible. Generally one bag is enough however larger or more severely affected cows may require two bags. Warm the solution to blood temperature (37°) before injecting under the skin. After injecting, rub the area firmly to spread the fluid, allow rapid absorption and to avoid problems such as swelling and infection. Cows that are staggering or down but able to sit up should recover in one or two hours. If the animal is not on her feet in two hours or is laying ‘flat out’ on her side, she may require a second bag. Calves should be removed from affected cows and should only be partially milked out for the next 48hrs to reduce the calcium drain and help prevent a relapse.


Managing the diet of high producing cows can be a valuable aid in preventing milk fever. Cows should be kept on a low calcium diet while they are dry (not lactating). By doing this, the body is stimulated to keep the blood calcium levels normal by mobilising the body stores of calcium from bones. When demand for calcium increases at calving, calcium can then be rapidly drawn from bone rather than feed therefore preventing milk fever.

Changing the cow’s diet during the transition period (4wks before to 4wks after calving) can also help reduce the occurrence of milk fever and other metabolic diseases by increasing the amount of calcium available to them.

Research has shown that cows with low blood magnesium levels have a greater chance of getting milk fever. There is evidence to suggest that a magnesium supplement such as magnesium oxide, will also help prevent milk fever. Magnesium oxide should be fed at the rate of 50g per cow per day, from at least 10 days prior to calving. Then feed a calcium supplement after calving to prevent further problems at 50g calcium/cow/day.

This information sheet is not intended as a substitute for a veterinary consultation. It is recommended that a consultation be arranged with a Veterinarian if you have any concerns with your herd’s health.