Calcium & Phosphorus Requirments
for Dogs
The raw facts about the ratio between calcium and phosphorus in the canine diet
Calcium and phosphorous are essential minerals in the body. The daily requirements vary depending upon the age and status of the dog or cat. Phosphorous and calcium deficiency and excess can occur and the ratio of calcium to phosphorous (Ca:P) is important.
Calcium
Of all the minerals, calcium is required in the greatest amount. Calcium is essential in the body for many functions including bone formation, blood coagulation, muscle contraction, and nerve impulse transmission. The calcium content of food ingredients varies widely. Bones, dairy products, and leguminous plants contain large amounts of calcium, whereas most
cereal grains, meat, and organ tissues contain small amounts.
Phosphorous
Phosphorous is the other dietary mineral required in a relatively high amount in the diet. Phosphorous is required at levels slightly less than calcium. Meat or organ meats are high in phosphorous but relatively low in calcium. Phosphorous deficiency is a significant problem in herbivores and is probably the most common mineral nutrition deficiency present in
animals worldwide. However, phosphorous deficiency occurs very infrequently in dogs and cats. In fact, excessive dietary phosphorous which accelerates the progression of renal failure is much more common.
Calcium:phosphorous ratio
Many foods that are low in calcium are high in phosphorous, and in addition, many foods that are high in calcium are equally high in phosphorous. Therefore, providing the correct calcium to phosphorous ratio in the diet can be difficult unless the proper minerals are added. It is very important that calcium and phosphorous be fed at the correct ratio of around 1.2 parts of
calcium for each 1 part of phosphorous (1.2:1).
Calcium and phosphorous requirements of dogs and cats
Growth Stage % Calcium in theDiet* % Phosphorousin the Diet*
Peak growth
and lactation 1.0-1.8 0.8-1.6
Half grown and
last trimester of
pregnancy 0.8-1.5 0.6-1.2
Adult
non-reproducing 0.5-0.9 0.4-0.8
*on a dry matter basis
Converting dry matter basis
All pet foods have different levels of moisture. Canned foods can have up to 80% moisture whereas, some dry foods can have as little as 6%. The reason for understanding percent moisture is to help you compare crude protein and fat between brands and between canned and dry. The listings on the label are for the food as it is fed, not as it would be on a dry matter basis. So without converting both brands of food to a dry matter basis you will not be able to compare them accurately. The conversion is not at all complicated.
If a dry dog food has 10% moisture we know that it has 90% dry matter. So we look at the label and check the protein level that reads 20%. Next, we divide the 20 percent protein by the 90% dry matter and we get 22%, which is the amount of protein on a dry matter basis. Does this make sense so far? Good. Now let us compare this to canned food that has 80% moisture. We know that with 80% moisture we have 20% dry matter. The label shows 5% protein. So we take the 5% and divide it by 20% and we get 25% protein on a dry matter basis. So the canned food has more protein per pound on a dry matter basis after all the water is taken out. We can do the same for fat, fiber, etc.
Calcium deficiency
The calcium:phosphorous ratio is very important. Calcium deficiency primarily results in animals fed diets high in meat and organ meats, which are high in phosphorous and low in calcium. If these animals are not adequately supplemented with calcium they may develop skeletal abnormalities often referred to as rickets. The bone could become soft or very thin and brittle. Feeding a raw diet which is balanced with the proper (Ca:P) ratio is easily accomplished by supplymenting calcium to levels proportionate to phosphorus and adiquate to the requirements for individual groth stages. Except for low calcium levels during pregnancy and lactation, (eclampsia) calcium deficiency rarely occurs any more and feeding a balanced diet can usually correct this problem. Feeding adequate calcium without the correct amount of phosphorous can prevent adequate uptake and utilization of the calcium, thus the calcium:phosphorous ratio is very important.
Calcium excess
Feeding high calcium diets with excess calcium is often blamed for contributing to bone problems in young, rapidly growing dogs. There does appear to be a link between the incidence of hypertrophic osteodystrophy (HOD), osteochondritis dissecans (OCD) and hip dysplasia, and the overfeeding of calcium. In recent studies, researchers fed dogs calcium at a much higher than recommended amount, and compared the incidence of disease in dogs that were fed normal or less than normal calcium levels. As would be expected, the animals that were overfed calcium showed increased incidence of skeletal problems including hip dysplasia.
Many people have embraced these studies and interpreted them to imply that by feeding a puppy food slightly lower in the recommended amounts of calcium and phosphorous to large breed puppies, the puppies will have a decreased incidence of hip dysplasia. However, there are no studies supporting this.
The large and giant breeds are the most susceptible to skeletal disease. Genetics, environment, and nutrition play key roles. Nutritionally, rate of growth, feed consumption, specific nutrients, and feeding methods influence our ability to optimize skeletal development and minimize skeletal disease. Maximizing the growth rate in young, growing puppies does not correlate to maximal adult size; however, it does increase the risk of skeletal disease. The growth phase of 3 to 8 months and possibly the phase prior to weaning are integral to ultimate skeletal integrity. The giant breeds may be limited in their ability to cope with excesses of minerals such as calcium, and the results are abnormal bone remodeling and skeletal disorders. This apparent increased sensitivity makes these breeds somewhat of a monitor of dietary influences.
Nutritional management alone will not be sufficient to manage developmental bone diseases. However, we can prevent some skeletal disease by appropriately feeding diets with optimized nutrients. Dietary deficiencies are of minimal concern in this age of commercial diets that are specifically prepared for young, growing dogs. The potential for harm is in overnutrition from excess consumption and supplementation.
Postpartum Low Blood Calcium in Dogs
"Eclampsia"
Eclampsia is a deficiency of blood calcium (hypocalcemia) that develops in the weeks after giving birth, although it may develop prior to birth or during lactation. Also called "milk fever" or puerperal tetany, eclampsia is usually due to an underactive parathyroid gland, the gland that is responsible for regulating the parathyroid hormone, which in turn regulates the amount of calcium that is stored in the bones, to be removed as needed for use in the blood. As the parathyroid gland has not being signaled to stimulate the parathyroid hormone to release calcium from the bones into the body, when the bitch's milk comes in and the demand for calcium suddenly increases, the parathyroid gland is unable to respond quickly enough for her needs to be met. The lack of calcium results in tonoclonic contractions of the skeletal muscles, where the muscles in the body contract convulsively, limiting movement.
This disease most often occurs with first litters and in toy breeds. Chihuahuas, miniature pinschers, shih-tzus, miniature poodles, Mexican hairless dogs and pomeranians are at increased risk for eclampsia, as as toy breeds and bitches with their first litters. However, puppies are often not affected by eclampsia because their nutritional needs, including calcium, are being taken care of by their mother. In addition, the symptoms typically become apparent in the first 40 days after giving birth, and rarely occurs during pregnancy.
Symptoms and Types
Poor maternal behavior
Restlessness, nervousness
Disorientation
Panting, whining
Vomiting
Diarrhea
Clumsy walking, stiff gait
Facial itchiness
Muscle tremors, tetany (entire body goes stiff), convulsions
Dog lies down with paws rigidly extended (usually seen 8–12 hours after the first onset of symptoms)
High body temperature, fever
Rapid, heavy breathing
Dilated pupils which are slow to contract when exposed to light
Causes
Calcium supplementation during pregnancy
Inappropriate calcium to phosphorous ratio in the diet while pregnant
Low body weight to litter size ratio
Poor nutrition during pregnancy
First litter
Diagnosis
You will need to provide a thorough history of your dog's health leading up to the onset of symptoms. Make sure to provide your veterinarian with the type of pregnancy supplement you have been giving to your dog, and details of the diet you have been feeding her.
Standard tests will include a chemical blood profile, complete blood count and an electrolyte panel. As soon as the electrolyte panel is ready, the total serum calcium will be verified by a blood test. If the concentration is less than 7 mg/dL, your dog will be diagnosed with eclampsia and will be given calcium supplementation immediately. Low blood sugar and low blood magnesium levels may also be present. These can also be supplemented. Serum potassium is high in 56 percent of cases. An electrocardiogram (ECG) showing the heart's electrical rhythm will often be abnormal.
Treatment
This is a serious and potentially life-threatening condition, but it can be treated quickly and the dog's health stabilized if she is treated as soon as symptoms become apparent. If your dog has a high fever, your veterinarian will try to cool her down with a cool water soak and fan to bring the body temperature down to a normal range. Your veterinarian will treat your dog with intravenous calcium until her levels have increased to a safe level, and until her body alone is able to maintain calcium levels.
Your veterinarian will advise you to take the puppies away to prevent them from nursing, to be hand fed with a commercial milk for 24 hours, or until the mother’s serum calcium is stabilized. If, after the mother stabilizes, you opt to let the puppies continue nursing, you will need to return to your veterinarian to monitor calcium levels in your dog's blood. Depending on whether her body is able to begin producing sufficient amounts of calcium on its own, she may need to remain on calcium supplements for some time. Your doctor will determine this.
Living and Management
If the puppies are not hand-raised and continue to nurse, it is very likely that your dog will need to be given calcium supplements for the duration of the nursing period, until the puppies have been weaned. Her serum calcium levels will need to be monitored frequently through the nursing period. Ensuring that she eats a diet containing a 1 to 1 or 1 to 2 calcium to phosphorus ratio, before pregnancy and during pregnancy, will help to prevent eclampsia with future litters.
Calcium supplementation must also be avoided while your dog is pregnant, unless specifically prescribed by your veterinarian. Also advised is avoiding high phytate foods, such as soybean mean, barley, rice, wheat bran and wheat germ, as high phytate foods can interfere with the body's absorption of calcium.
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