Vet on call: Understanding milk fever in cows - Daily Nation

Vet on call: Understanding milk fever in cows

Saturday January 12 2019

A dairy cow suffering from milk fever on a farm in Murang'a.

A dairy cow suffering from milk fever on a farm in Murang'a. The disease occurs when the feed does not have enough calcium or the body is not able to release enough of it into the blood from the bones. PHOTO | JOSEPH MUGACHIA | NMG 

By DR JOSEPH MUGACHIA
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As long as farmers keep dairy cattle and continuously strive for higher yields, they will at one time or another encounter cases of milk fever.

I explained the disease in Seeds of Gold of January 14, 2017. However, this week, I met two farmers in a function and they said they thought there was an outbreak of milk fever in their village in Murang’a.

They have seen a number of dairy cows go down after calving. Some recover after treatment but some do not.

One of the farmers was concerned that his cow was said to have had both milk fever and nerve damage. Another was diagnosed with nerve damage after a difficult calving. He wondered when to diagnose nerve damage or milk fever.

At the same time, I have been treating a difficult case of milk fever in Thika during the week. The high-yielding pure Friesian cow was initially treated by my colleague after an easy twin calving.

The cow had responded well to treatment but the doctor noted it had consumed 800ml of 40 per cent calcium solution intravenously and 400ml under the skin.

That was a larger than usual dose. Soon after the infusion of the medicine, the cow had coughed, brightened up and stood up on her own and immediately started eating.

My colleague, Dr Mwikali, had also noted the case presented unusually because the cow was eating while lying down but the eyes were dull.

The nose was dry and the rumen and heart movements were weak. That led her to diagnose milk fever, but not showing the typical signs of groaning and placing the head on the side against the chest.

Most diseases present in a prescribed manner based on the documented most observed signs. This is medically termed the classical presentation.

Some diseases may, for some known or unknown reason, show only a handful of signs thereby prompting the doctor to diligently look for indicators of other diseases before concluding that the disease is showing an incomplete picture. This type of presentation is called atypical.

The milk fever case I have been treating this week was truly atypical. I was called three days after the initial treatment and informed the cow had again gone down, was eating and ruminating but would not stand, even with human assistance.

Upon examining the animal, I returned the same findings as Dr Mwikali. I, however, noted the muzzle was semi-dry.

COMMUNICATING WELL AGAIN

The muzzle of a normal cow is always very wet. Normally, animals treated for milk fever will respond and rarely show the disease again in the current lactation.

Furthermore, this cow was being given a calcium salt in the feed since the last treatment. She should not have been struggling with milk fever again.

This being an unusual case, I collected blood samples for laboratory analysis before commencing treatment. I proceeded to give calcium solution intravenously into the jugular vein.

After infusing each 200ml of the solution, I would check the heart and rumen movements to gauge the response to treatment to avoid overdosing since the cow’s situation was not the typical milk fever. I would also monitor the wetting of the muzzle and the status of the eyes.

After infusing 800ml of the solution, the cow’s muzzle became fully wet, the heart beat strongly and the rumen sounds became loud and strong.

The cow also shook its head and was able to leak its nostrils. It voided a lot of dung and urine — signs that the nerves and muscles were communicating well again.

The cow attempted to stand but would only get halfway up before going down again. I attributed that to lying-down fatigue and the fact that the nerves and heavy muscles of skeletal support may not have got fully activated.

I gave another 400ml of calcium solution to the cow under the skin so that the mineral could be absorbed slowly into the blood, according to the body’s requirements.

I instructed the farm manager to keep urging the cow to stand in periods of 10 to 20 minutes over the next two hours and report progress.

I also told him to reduce the calcium salt in feed to about 50 grammes daily to avoid overload.

He told me the cow had stood about an hour after I left. Analysis of the blood showed the cow had minimal calcium levels, high sodium and low magnesium.

Other minerals lay within the normal range. The variation in calcium, sodium and magnesium levels could have caused the atypical presentation observed in the case.

Animal health service providers should treat all cases of milk fever according to the signs observed and only take blood samples for analysis in the few cases that show unusual signs and response to treatment.

For the farmers who thought their area had an outbreak of milk fever, my advice was that milk fever really does not occur in outbreaks.

ENOUGH CALCIUM

It is more of an individual cow problem and the disease is not an absolute lack of calcium in the body but the inability of the animal to manage and keep the balance of the blood calcium and the calcium in the bones. Medically, this is called calcium homeostasis.

Under normal circumstances, the body has a mechanism that collects excess calcium in the blood and stores it in the bones.

When calcium levels lower in the blood because of increased demand like during pregnancy and heavy milking, the body releases calcium from the bones and returns it to the blood. In the meantime, the body also keeps absorbing calcium from the feed eaten and gets it into the blood.

Milk fever occurs when the feed does not have enough calcium or the body is not able to release enough of it into the blood from the bones. It is not well-known why the switching mechanism fails.

However, the failure is associated with inadequate intake of calcium, excessive uptake of calcium and a heavy demand for calcium for foetal bone formation or milk production.

It is also thought some family lines may contain genes that make it easier for animals in such families to get milk fever attacks.

To avoid milk fever, farmers should feed their pregnant and early lactation cows dairy mineral salts of high quality and follow the manufacturers’ instructions on the recommended daily intake per cow in the various stages of production.

I have seen farmers feeding dicalcium phosphate excessively during pregnancy and they end up with milk fever before or after calving.

Dicalcium phosphate should only be given under the instructions of a veterinary doctor since it is more of a medication rather than a balanced dairy salt.

It is possible for a cow to go down because of both nerve damage and milk fever. A cow with milk fever can also damage its leg and hip nerves and muscles while attempting to stand. This happens mainly when the muscle paralysis is incomplete and the cow ends up spraying the legs.

A cow that is not getting up should be kept under shade to rest until the doctor arrives to make a diagnosis and give treatment.

Animals with nerve damage alone will look normal except loss of feeling in the hind legs. This mainly occurs when cows had difficult calving.

They fail to stand after the calving while milk fever cows will normally stand and then go down later.