Having a calf and transitioning from a dry cow to a lactating cow is a big deal.
During this time the dairy cow goes through enormous physiological changes, and she requires a careful evolution of her diet to match these changes.
If the right balance is not achieved, there is increased risk of serious and life-threatening imbalances of minerals such as calcium (milk fever), magnesium (grass staggers), or excessive breakdown of body tissue to meet the energy demands of lactation (ketosis). As we roll around to another calving season, it’s worth reviewing the key features of these important conditions.
Milk fever
What is it? Milk fever, or hypocalcaemia, is a sudden fall in blood calcium and it usually occurs within a few hours of calving due to the calcium demands of milk production.
At this time the cow’s demand for calcium increases suddenly, and more quickly than her body system can adapt to. She is unable to mobilise enough calcium from bone stores or the gut to maintain adequate calcium levels in the blood. Calcium is important for muscle function, and so the signs of milk fever reflect lack of muscle strength and tone.
Signs: Milk fever should be considered an emergency. Early signs are weakness, unsteadiness, depression and glazed eyes. If untreated, the cow may go down, there may be a S-shaped bend in the neck, a dry nose with no muzzle sweat, dilated pupils, constipation, low temperature, a fast but weak heart rate and an inability to rise.
Treatment: Administer calcium borogluconate solutions into the vein (IV). Suitable products are CBG 37.5, Glucalmag, Glucalmax or Glucalphos. Slow (emphasis on slow) IV injection is preferred as injections of calcium given under the skin (SC) take longer to be absorbed. Ask your vet to train you on safe and correct treatment techniques. When the cow has recovered its ability to rise and is able to swallow, oral calcium supplements may be given to help prevent a relapse.
Prevention: Careful management of dry cow feeding and mineral intake. Magnesium supplementation pre and post calving is important. Consult your vet for details on correct transition mineral management. In addition, the administration of oral calcium products at calving or shortly after may also help. Examples of oral products are Oral Cal or Oral Max.
Grass staggers / Grass tetany
What is it? Grass staggers, or hypomagnesaemia, usually occurs within six weeks of calving and results from low magnesium intakes or absorption. Grass staggers are often precipitated by bad weather and grazing of lush pastures. Magnesium is also important for preventing milk fever.
Signs: Signs include twitching of the ears, frothing at the mouth, bellowing, muscle tremors and aggression. This is followed by spastic (stiff) gait, incoordination, muscle spasms, recumbency, paddling of the limbs, convulsions, coma and death. The heartbeat is strong and fast and may be heard when standing close to the cow. Although many of these cases may die, early treatment can lead to complete recovery.
Treatment: It is a condition requiring urgent attention. Treat with injectable magnesium preparations. Mag20 should only be administered SC (under the skin) – NOT IV. Glucalmag, Glucalphos or Glucalmax may also be administered SC or alternatively by very slow IV injection to avoid heart failure.
Prevention: Magnesium supplementation, provide shelter during rough weather and talk to your vet.
Ketosis (acetonaemia)
What is it? Ketosis occurs when the energy demands of lactation exceed what’s available from the diet and the cow breaks down body fat and muscle.
Signs: Ketosis usually occurs within two to eight weeks after calving and you may observe a rapid loss of bodyweight / condition, inappetence, dull coat, firm faeces and glazed eyes. Alternatively you may see signs of hyperexcitability, pica (aberrant feed selection) and aggression.
Treatment: Drenching twice daily for three to four days with Ketol, that provides a concentrated source of energy, helps to support blood glucose levels.
A cow’s appearance can be complicated by a combination of these conditions occurring at once. Before calving season arrives, ask your vet to train you and your staff on recognising these diseases, prevention measures, and the safe and correct treatment techniques. For animals that don’t respond to first line treatment, seek veterinary advice.
CBG 37.5, Glucalmag, Glucalmax, Glucalphos, Oral-Cal, Oral-Max and Ketol are registered under the ACVM Act 1997, No. A004633 No. A004047, No. A001441, No. A001442, No. A007669, No. A009642 and No. A000110. CBG 37.5, Glucalmag, Glucalmax, Glucalphos, Oral-Cal, Oral-Max, Ketol, Elanco and the diagonal bar logo are trademarks of Elanco or its affiliates. Elanco New Zealand, 106 Wiri Station Road, Manukau, Auckland 2104. www.metabolicsolutions.co.nz 0800 446 121. © 2025 Elanco.
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