When improved-breed and high-yielding cows are about to calve or have just calved, farmers often complain that the cow has fallen after calving and cannot get up. She seems almost dead, her legs limp. They quickly call an experienced veterinarian, and with treatment the cow recovers. The disease is called milk fever.

It is the only disease with "fever" in its name in which no fever is actually seen. The disease is very familiar in Bangladesh's climate, especially among those who keep improved and good-quality crossbred cows. It does not occur at every calving, but it is often seen around the time of calving, and it makes some people afraid to keep cows. Milk fever is a metabolic disease, usually caused by calcium deficiency.

It is a nutrient-deficiency disease that occurs when the body lacks the calcium it needs to function properly. At calving the calcium shortfall is very large, which is why the cow suddenly falls and sits with her head turned towards her neck.

Normally 100 cc of blood should contain more than 9 mg of calcium. For particular reasons this can fall sharply, even to 3–4 mg, and that is when the disease sets in. It can also occur if the placenta is retained in the uterus at calving, if the uterus prolapses for any reason, or if the calf is stuck somewhere in the uterus.

Other causes include adverse hormonal activity, such as variations in adrenal gland secretion; disruption of normal biological processes through deficiencies of various minerals in the cow's body; and milking the udder completely empty after calving.

During pregnancy the cow sends calcium from her own blood to the foetus, roughly 10 g a day. Within 24 hours of calving, about 1 g an hour, or up to 30 g a day, leaves the body in the milk. That is why the disease is more common when adequate calcium is not supplied during pregnancy and after calving.

Calcium can also fall when the amount absorbed from the gut and released from the bones is far below what the foetus and colostrum demand, or when calcium is not properly absorbed in the gut during pregnancy and the colostrum period. Poor absorption can result from a lack of calcium in feed, the formation of insoluble calcium oxalate in the small intestine, intestinal inflammation, an imbalance in the calcium-phosphorus ratio and a lack of vitamin D.

The disease affects high-yielding cows in every country, including Bangladesh, and sometimes goats, ewes and buffaloes too. Milk fever occurs sporadically, but there is a history of 25–30 per cent of cows on farms being affected. Symptoms usually appear at three stages: in the last few days of pregnancy, at calving, and after calving (up to 48 hours).

The disease causes a temporary drop in milk production, so the farmer suffers financially. With prompt treatment the cow recovers, but if treatment is delayed too long any complication may follow. The death rate is low.

Despite the name, there is no fever. The cow's temperature falls, or sometimes stays normal. Symptoms fall into three stages.

• First stage: mild excitement and involuntary muscle twitching; nervous weakness, hypersensitivity, loss of appetite and weakness; reluctance to walk and eat, then stiff hind legs and a staggering gait; a faster heart rate and a slight rise in body temperature. These signs are brief and can pass unnoticed, while blood calcium falls below normal.
• Second stage: the cow lies down and cannot get up again. She lies with her head and neck turned and resting on her flank. Partial paralysis and depression appear, and blood calcium falls much further. There is fine muscle tremor and a deep, rapid heart rate. The extremities, especially the ears and nose, are cold, and body temperature is 96–100 degrees Fahrenheit.
• Third stage: the depressed animal lies on its side with its head tucked in, a posture characteristic of milk fever. The belly bloats. Untreated, the cow dies. Blood calcium falls to its lowest (1 mg/dl).

If milk fever strikes before calving, labour starts and then stops; the cow does not strain to deliver, and inactivity of the uterus disrupts calving. If the calf is born, hypocalcaemia can lead to prolapse of the uterus.

Diagnosis usually rests on the following: the history of pregnancy and calving, as the disease is more common in mature cows, especially those aged 5–9 years; a cow normally stands 15 minutes after calving, a heifer after 30 minutes and a cow with a difficult calving after 40 minutes, so if she does not stand within this time milk fever should be suspected and tested for; matching the signs with the known symptoms; and measuring blood calcium, phosphorus and magnesium.

Consult an experienced veterinarian as soon as symptoms appear, and the problem can be solved quickly. Calcium borogluconate solution should be injected as soon as possible. A cow of about 450 kg body weight is given 500 ml of calcium borogluconate, containing about 108 g of calcium, half under the skin and the other half into a vein over 5–10 minutes.

When the right amount of calcium enters the blood correctly, the cow responds quickly and recovers, though the source notes that some cows (it gives a figure of about 15) are kept apart for further treatment or culling. If treated with too little calcium solution, the cow neither recovers nor stands, or recovers temporarily only to face the same problem again. On the other hand, giving calcium solution in excess and too fast into the vein risks killing the animal.

Solutions combining calcium, phosphorus, magnesium and glucose are now available on the market. In milk fever calcium and phosphorus levels fall but magnesium rises, so care is needed in choosing the medicine.

Prevention is better than cure, and it can be built in two ways: feed correction and correction of predisposing factors.

Feed correction can include giving calcium-rich feed while the cow is dry. But calcium alone should not be given at that time, because it makes the body depend entirely on calcium absorbed from the gut, leaving calcium mobilisation from the bones almost inactive; then, when calving and colostrum demand large amounts of calcium, it cannot be mobilised quickly from the bones. Feed should supply adequate phosphorus, and mixing 15 per cent monosodium phosphate into the cow's concentrate feed helps prevent the disease.

Correcting predisposing factors means giving older cows adequate care, and taking special care and management to protect Jersey cows from the disease, as well as ensuring balanced nutrition for the cow while dry, at calving and after calving.

With a little awareness in managing our cows, we can easily protect them from this disease, and if it does appear, prompt action brings a quick recovery. Milk production will then stay normal and farmers can profit.

Source: Staff Correspondent. First published in Bengali on The Agro News.