Hypocalcemia is defined as an insufficient level of calcium in the blood. Eclampsia, once also called puerperal tetany, is one of the results — in fact, the most important one. In cattle, eclampsia has been known in some areas as “grass staggers” but it occurs in non-grass-eating animals such as dogs and cats, also. Homeostasis (optimal balance) of calcium is mainly regulated by parathyroid hormone, calcitonin, and vitamin D.
In dairy cows, short-term hypocalcemia usually occurs near parturition when mammary gland secretions more than double the cow’s requirements for calcium. This calcium must come from metabolized food or the animal’s own bone, or both, but such transfer is not always fast enough, and the cow “goes down.” The dairyman must be right there to administer a shot of calcium gluconate (the most soluble and safe calcium salt), or the cow could die. It also happens in dairy goats, but far less often.
Eclampsia (sometimes erroneously called “milk fever”) is an acute and life-threatening emergency condition seen in animals shortly before or shortly after birthing their offspring — a calf or a litter, for instance. In bitches, eclampsia can be marked by one or more of these signs: nervousness as exhibited by pacing, panting, trembling/shaking, unwillingness to nurse, elevated blood pressure, edema, tetany, convulsions, seizures, paresis/paralysis, and even coma which can lead quickly to death. The very first signs of hypocalcemia (insufficient calcium circulating in the blood) that leads to eclampsia are commonly missed: excitement or other behavioral aberrations, and perhaps muscle twitching. If you are in the dog’s company you should notice the next signs, though: weakness, paresis, and perhaps convulsions and epileptic-like seizures. Certainly not all afflicted animals show all or the same signs, but others that have been reported include dilation of the dog’s pupils, faster pulse rate, and elevated body temperature, all of which can be very, very serious.
It is most common in toy breeds, in (often, hyperactive) bitches with large litters. The big factor seems to be a very low ratio of dam’s body size to her litter size (and consequent milk production demand). Fortunately, most toys have only one to three pups, but the combination of a very small breed with many whelps carries a higher risk. A tiny bitch with a large and late-nursing litter requiring large amounts of calcium-rich milk is taxed concerning her ability to keep enough calcium in her own bloodstream while keeping up enough milk production for the pups. Nature often gives calcium and other-nutrients priority to whelps over the dam’s needs until it gets to the point of survival, and then instinct may cause her to kill off those hungry leeches in order to survive for hopefully better conditions in the future. Some claim that such post-partum eclampsia hysteria or instinct to survive at the expense of her whelps may be a survival manifestation.
The disease in household pets occurs most frequently in small, hyperactive dog breeds and occasionally in cats. In dogs, the greatest risk of hypocalcemia comes at peak lactation; i.e., when the demand by growing pups is greatest just before they start ingesting enough prepared food in place of or in addition to mother’s milk. This is often about 3 to 4 weeks after delivery. If your bitch is treated for hypocalcemia-with-eclampsia, it is advisable to hand-rear the whelps for at least 24 hours after treatment. An experienced breeder might be able to show you how to tube-feed. However, as I said, prevention is preferable. Normally, this is accomplished by insuring that the bitch has a good-quality, highly digestible ration especially in her third trimester (in cats, all during pregnancy). I recommend supplementation or partial replacement with eggs, cottage cheese, and meat, in order to maintain digestibility without excessive bulk that comes from grains, and to approximate the ideal calcium-phosphorus ratio of between 1:1 and 1.4:1. Almost never would calcium supplementation outside of such a partial dietary approach be healthy. It would be very rare if the dog needed a different ratio, and then only under supervision of a board-certified nutritional expert.
Although the dangers of calcium pills or powders added to a good normal diet have been explained over and over in the past 30 or 40 years, breeders who do not “read up” (keep current) on the science of breeding and nutrition often give brood bitches calcium-pill supplements during pregnancy or even all during life. This practice not only does not prevent eclampsia, it can actually contribute to its occurrence during future pregnancies. These changes decrease the ability of the dog to extract or shift calcium from its bone “storage rooms,” when more of the mineral is needed for milk. It takes 1 to 3 weeks to reverse the effects. Of course, this is not fast enough, and this is why hypocalcemia and eclampsia occur even if you recently improved the dog’s diet.
I recommend you get my book “The Total German Shepherd Dog” (Hoflin, publ.) which has some 17 chapters good for any breed. In it, you will find a more detailed treatment of the subject explaining how excess dietary Ca can actually stimulate calcitonin production, decrease the intestinal calcium absorption efficiency, and inhibit parathormone secretion. If in the USA, you can order an autographed copy from me, with or without the (highly recommended!) book on canine orthopedics, also good for all breeds.
It would do no good to try giving affected dogs calcium-rich foods by mouth, because it would take too long (as much as weeks!) to be assimilated and to reverse the effects, and the dog’s swallowing reflex might be affected and you could get the milk or yogurt into the lungs. It is imperative to act quickly, and that might mean giving the dog an intravenous shot of calcium gluconate, such as my dairy manager friend does to the cows in his charge. (Subcutaneous injection in dogs can cause necrosis of tissue at the site.) But the amount is tricky to control, and unless you do it as a regular practice, you could mess things up even worse. Even veterinarians might not see enough cases in dogs, to be used to handling canine emergencies with aplomb. Best is to try to prevent it, although that is not an easy matter, either. By the way, that friend I mentioned had charge of Jersey cattle, a breed that is gentle in expression, pleasant in appearance, and known for producing the highest butterfat-content milk of any bovine breed.
As a 1946 veterinary study remarked, incidentally, “It will be noted that the incidence of milk fever is much higher in the Jersey breed [33.3%] than in the other breeds [9.6%].” So I had more opportunity to discuss the problem than most dog breeders. That same study concluded that irradiated (killed) yeast, a common source of vitamin D precursor supplement, reduced the incidence of milk fever somewhat in Jersey cows which had previous histories of milk fever. So if you have a bitch with a history of eclampsia and still want to take chances because you see things in her that you do not want to lose in your breeding program, you might want to research the idea of vit.-D supplementation.
“Homemade” diets, often poorly designed, are more hazardous at this time in those breeds susceptible to the problem. Too much meat (imbalanced proportion) could be as dangerous to some individuals as too much calcium supplementation. The reason is that if you swing the balance too far out of kilter, the body seems to over-react and go too far the other way. It’s like trying to steer a car with tie-rods ready to fall off. Liver is great for “loosening up” the dog’s bowels so that it can defecate easier during the last few days before whelping, but if started too early and too much, its 1 to 15 Ca/P ratio can cause the dog’s system to be too low in calcium, and predispose it to eclampsia. On the other hand, too much calcium can have a backlash effect and make the system nearly stop all calcium assimilation, and give the same result.
Treatment is best carried out in the emergency vet’s clinic. They will probably insert an “I.V.” (intravenous) catheter with a slow drip (too fast or too much can cause severe cardiac arrhythmia, so the heart rate must be monitored during this procedure). Concurrently, dextrose may also be administered via the vein, to boost the energy level of the bitch who has probably been exhausted by muscle tremors. A sedative might be needed before that takes effect, and lowering body temperature to combat fever is sometimes called for. So, you see, this is not something that you should do by yourself.
As regards prevention other than a good normal diet for a bitch of a susceptible breed and judicious supplementation during her pregnancy, you might want to supplement the puppies’ nourishment with milk replacer (Esbilac, goats’ milk, etc.) as soon as they will handle it, in order to decrease the milk demands on the dam. I have “successfully” weaned pups as early as 10 days of age, though I would not recommend it as a general practice because you might be depriving them of some immune system support that could last the rest of their lives. But since recurrence in the same or subsequent lactation periods is common, you not only want to keep a close eye on her, but also cross her off the list for future consideration for additional litters.
Of course, there will be some who would disagree with me on the emphasis I place on probable genetic or inheritable influences, and would recommend changes in pregnancy and nutrition management, pointing to environmental influences. Namely, the connection between poor nutrition during pregnancy/lactation (including use of calcium supplements prior to and during pregnancy) and incidence of hypocalcemia and eclampsia. They might even point to such retrospective studies as the one reported in the AVMA Journal, in which twelve (39%) dogs with eclampsia had previous litters and none had a history of eclampsia. But I have studied genetics for so long that I have become convinced of its ponderous weight of evidence in most disorders. The predisposing factors of breed, body type, etc. strongly point to heritability, as far as I am concerned.
Hypocalcemia/eclampsia has been called by some “a metabolic disease” but that is a poor term in my understanding of etymology. As a writer named David Pethick has phrased it, “In all diseases, the metabolism of the animal is abnormal.” While not conforming to classical logic, one might reverse that concept and say that all cases of abnormal metabolism are disease conditions. It is a phrase of convenience, because the more accurate is rather cumbersome: a biochemical change of non-infectious origin in an animal which has been subjected to animal husbandry, resulting in an increase or decrease in a metabolite critical to the function of the animal and induced by an imbalance in the input or output of the metabolite or a related metabolite. A bit much, right?
Whatever you decide to call it, this type of disease state “is common in lactating or pregnant farm animals, where the rate of metabolite uptake from blood to the mammary gland or fetus is high.” When seen in these farm animals, it is also called “a production disease.” Cows are not dogs or cats, and while symptoms in dogs are similar to the disease in ruminants and even though they are all mammals (milk producers), we must be careful in drawing conclusions. The disease etiology in the canine and feline has not been studied in detail. The main difference is that these companion animals are most susceptible at peak lactation (one to three weeks post-partum) while in cows the incidents most commonly (75%) occur within 24 hours of calv¬ing. “Milk fever” is rare in cows during full lactation. A seemingly paradoxical finding is that milk fever in cattle can be prevented by feeding low-calcium diets in the last few weeks of preg¬nancy. But this may be related to the same phenomenon seen in canine nutrition, of both extremes in calcium levels having similar end-results because they both disrupt normal calcium deposition, resorption, loss, and circulation. The old theological advice might be appropriate in pet nutrition: “Moderation in all things.”