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= = =**Hypocalcemia** =

Milk fever, post-parturient hypocalcemia, or parturient paresis is a disease, usually of dairy cows, characterized by reduced blood calcium levels. It is most common in the first few days of lactation, when demand for calcium for milk production exceeds the body's ability to mobilize calcium reserves. "Fever" is a misnomer, as body temperature during the disease is usually below normal. Low blood calcium levels interfere with muscle function throughout the body, causing general weakness, loss of appetite, and eventually heart failure.

Hypocalcemia is more common in older animals (who have reduced ability to mobilize calcium from bone) and in certain breeds (such as Jersey cattle). Hypocalcemia, like milk fever, occurs occasionally at any time during the lactation or pregnancy and in many mammalian species.

**Clinical symptoms**

In mild cases, the animal seems quite normal, but has difficulties standing. If the cow succeeds in rising, she staggers, and will very soon fall. The cow's appetite can be maintained at that stage. Body temperatures are from 37 to 38.5°C (normal range 38-38.5°C). This stage, referred to as "first degree", corresponds to calcemiae of 55 to 75 mg/l.

In typical cases, the cow's head is in a so-called self-auscultation position. Mydriasis is often present. The heart can be slow or arrhythmic. The body temperature is 35 to 37°C. In that stage, referred to as "second degree", calcium levels in the blood are of 30 to 65 mg/l.

In advanced cases, the cow is lying on its side, seeming dead. The body temperature can go as low as 32°C. This is the 3rd degree, with calcemia as low as 20 mg/l.

**Treatment**

Treatment generally involves calcium injection by intravenous, intramuscular or subcutaneous routes. Before calcium injection was employed treatment comprised inflation of the udder using a pneumatic pump. Inflation of the udder worked because the increased pressure created in the udder pushed the calcium in the udder back into the bloodstream of the cow.

Intravenous calcium, though indicated in many cases, is potentially fatal through "heart blockade", or transient high calcium levels stopping the heart, so should be administered with care.

In unclear cases of downer cows, intravenous calcium injection can lead to diagnosis. The typical reaction will be a generalized tremor of the skeletal muscles, and sometimes cardiac arrhythmia. Defecation, urination and eructation are frequent during the treatment, due to pharmacological effect of calcium on the smooth muscles. In stage I and II, The cow can stand up approximately 10 minutes after the end of the intravenous injection. But in stage III, it may take two or three hours. If the cow is in stage III and lying on its side, it is important to put the cow in a sternal position or else risk aspiration.

The prognosis is generally good, even in advanced cases. However, some cows can relapse the following day, and even a third time the day after.

**Prevention**

Proper dietary management will prevent most cases of milk fever. This generally involves close attention to mineral and fiber levels in the pre-calving diet as well as improving cow comfort to eliminate other problems that may interfere with appetite and so trigger hypocalcemia.

Oral administration of a dose of a calcium salt in a gel have been advised by some veterinarians.

**References**

<span style="border-collapse: collapse; font-family: arial,sans-serif; line-height: normal; white-space: pre-wrap;">Veterinary Medicine (5th ed.), London: Baillière Tindall, 1979, pp. 827–836 (Parturient paresis or milk fever) <span style="border-collapse: collapse; font-family: arial,sans-serif; line-height: normal; white-space: pre-wrap;">Lucien Mahin (1977-2008), Observations on diseases of cattle in Morocco (unpublished data) <span style="border-collapse: collapse; font-family: arial,sans-serif; line-height: normal; white-space: pre-wrap;">Nidermeier, R.P.; Smith, Vearl R. (1950), "The Effect of Udder Inflation Upon Blood Levels of Calcium, Magnesium and Phospherous in Cows with Parturient Paresis", Journal of Dairy Science 33: 38–42 <span style="border-collapse: collapse; font-family: arial,sans-serif; line-height: normal; white-space: pre-wrap;">Haalstra, R.T. (1973), Tijdchrift voor Diergeneeskunde, 98, pp. 529


 * Calcium Balance**

Calcium is critical to the function of most cells: It triggers exocytosis of chemical messengers, stimulates secretion of various substances, stimulates muscle contraction, and increases the contractility of the heart and blood vessels. Calcium is also an important component of the bone and teeth. An increase in plasma calcium, called //hypercalcemia//, has widespread effects on the body, including muscle weakness and atrophy, lethargy, behavioral changes, hypertension, constipation, and nausea. A decrease in plasma calcium, called **//hypocalcemia//**//,// causes numbness and tingling sensations, muscle cramps and spasms, exaggerated reflexes, and hypotension.

Plasma calcium concentration is regulated through the interaction of a number of organs, including the kidneys, digestive tract, bone, and skin (Figure 19.20). Calcium can be added to the plasma from bone and absorbed via the digestive tract, and it can be removed from the plasma by bone and the kidneys. Even though most of the calcium in the body (99%) is located in the bones, this calcium is not permanently fixed in the bone. The bone actually provides a reservoir of calcium such that when plasma calcium levels are low, the plasma can obtain calcium via a process called //resorption,// during which bone is broken down to liberate calcium ions. Conversely, when plasma calcium levels are high, calcium can be deposited into bone. The body also obtains calcium from ingested food. Although the absorption of most substances by the gastrointestinal tract is not regulated, calcium absorption is regulated according to the needs of the body.


 * Renal** **Handling of Calcium Ions**

Calcium is transported in blood both bound to carrier proteins and free in the plasma. Calcium that is free in the plasma is freely filtered at the glomerulus. Normally, 99% of the filtered calcium is reabsorbed as the tubular fluid moves through the renal tubules. Approximately 70% of the filtered calcium is reabsorbed in the proximal tubules, 20% is reabsorbed in the thick ascending limbs of the loops of Henle, and the remaining 10% is reabsorbed in the distal tubules. Reabsorption in the loops of Henle and the distal tubules is regulated by hormones.


 * Reference**

Stanfield, C. L. and Germann, W. J.2009, ‘Principles of Human Physiology’ third edition, pg 533-534, Pearson, San Fransisco.