Disorders of Calcium Metabolism in Dogs
Calcium is an essential component of the skeleton, and it has important functions in muscle contraction, blood clotting, enzyme activity, the nervous system, and hormone release, among others. Many different metabolic disorders affect calcium metabolism and can lead to abnormally high or low levels of calcium in the blood (See also Disorders of the Parathyroid Glands and of Calcium Metabolism in Dogs).
In dogs, the most common disorder of calcium metabolism is puerperal hypocalcemia. Other names for this condition include postpartum hypocalcemia, periparturient hypocalcemia, puerperal tetany, and eclampsia. This life-threatening condition is usually seen 2 to 3 weeks after whelping, when the mammary glands are producing the greatest amount of milk. Small-breed dogs with large litters are affected most often, although puerperal hypocalcemia can occur in any breed of dog, with any litter size, and at any time during lactation. Hypocalcemia most likely results from loss of calcium into the milk and too little calcium in the diet.
Panting and restlessness are early clinical signs. Tremors, twitching, muscle spasms, stiffness, and incoordination may also occur. The dog may become disoriented, hypersensitive, and aggressive, and whine, drool, and pace. Severe tremors, repeated and prolonged contraction of muscles, rapid heartbeat, fever, seizures, and coma may develop. Usually, the dog has been otherwise healthy, and the newborns have been thriving. Although hypo-calcemia usually occurs after giving birth, clinical signs can appear before or during the act of giving birth. Hypocalcemia can contribute to ineffective contractions and a slow labor without causing other clinical signs.
A tentative diagnosis is based on the history, physical examination, clinical signs, and response to treatment. A blood test to determine the level of calcium confirms the diagnosis.
Immediate veterinary treatment is needed for dogs with puerperal hypocalcemia. Calcium solutions given intravenously usually result in rapid improvement within 15 minutes. Puppies should not be allowed to nurse for 12 to 24 hours. During this period, they should be fed a milk substitute or other appropriate diet; if mature enough, they should be weaned. If signs recur in the same lactation, the litter should be hand raised (if younger than 4 weeks) or weaned (if older than 4 weeks). After the acute crisis, calcium supplements are given for the rest of the lactation. Vitamin D supplements also may be used to increase calcium absorption from the intestines. Blood calcium levels are usually monitored weekly.
Puerperal hypocalcemia is likely to recur with future pregnancies. Preventive measures in dogs include feeding a high-quality, nutritionally balanced, and appropriate diet during pregnancy and lactation, providing food and water ad lib during lactation, and feeding puppies with supplemental milk replacer early in lactation and with solid food after 3 to 4 weeks of age. Oral calcium supplements should not be given during pregnancy because they may actually cause rather than prevent hypocalcemia after the dog gives birth.