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I want to talk a little about calcium during whelping.
First, please see this post to learn more about the role of calcium during whelping as well as a critical warning about not using calcium prior to onset of active labor—this can cause eclampsia and kill your bitch.
The parathyroid gland controls the release of calcium needed to produce milk. When calcium is given prior to onset of active labor, the parathyroid gland doesn't regulate properly (it gets "lazy") and won't always release calcium adequately from the bones to support lactation. This results in a dangerously low level of calcium in the bloodstream and can cause eclampsia, which is often fatal if not immediately corrected. Eclampsia is a medical emergency and can kill before you can even get to the vet clinic.
Once active labor starts, it is safe to start supplementing calcium. Calcium supplementation not only assists with milk production, but it alleviates many behavioral problems some people incorrectly label as bad mothering: excessive digging, aggression toward puppies, restlessness, rejection of puppies. These behaviors are actually signs of low blood calcium.
Most breeders with any experience realize this. However, there's a lot of misinformation about the best source of calcium and not much knowledge about how much to give. There are varying reports, and when in doubt consult a board certified reproductive veterinarian.
How much to give?
We use a dose of 75-90 mg of elemental calcium per pound of her pre-pregnancy body weight. This much calcium should not be given all at once, but should be split between puppies when whelping, and across 3-4 meals when nursing. This much calcium should not be given all at once.
Here's one area where there's a lot of confusion: elemental calcium is not usually listed on packages unless it's a supplement specifically designed for calcium supplementation, such as Oral Cal Plus or Calsorb.
Here are some rough ranges for various weights:
5 lbs—375-450 mg elemental calcium
10 lbs—750-900 mg elemental calcium
20 lbs—1,500-1,800 mg elemental calcium
30 lbs—2,250-2,700 mg elemental calcium
40 lbs—3,000-3,600 mg elemental calcium
50 lbs—3,750-4,500 mg elemental calcium
60 lbs—4,500-5,400 mg elemental calcium
70 lbs—5,250-6,300 mg elemental calcium
We give this amount through peak lactation. Always contact your reproductive veterinarian prior to whelping to confirm these amounts are correct and suitable for your dog. While your regular vet may do a great job, unless your vet specializes in reproductive medicine, they may not be aware of how much calcium to supplement. Whenever possible, we recommend a board certified reproductive veterinarian. In particular, dogs with health issues such as kidney problems, urinary problems (including UTIs), diabetes, clotting disorders, and heart problems should consult a veterinarian prior to calcium administration. Let your vet know what form you will be using, as calcium supplements can contain other ingredients in addition to their calcium source.
PLEASE DO NOT STOP READING AT THIS POINT AND THINK YOU KNOW HOW MUCH TO GIVE—you need to determine the type of calcium you are giving to know how much of your supplement to use. Please read on! There's a table further down that includes amounts of commonly used calcium-containing products.
Kinds of calcium
Elemental calcium is the pure atomic form of calcium that you see on the periodic table, often abbreviated as Ca. Calcium generally doesn't exist in its elemental form—it needs to bind with another element to form a molecular compound. Each compound has different proportions of calcium and the other element(s), so they each have different amounts of elemental calcium per milligram or other measurement. Common forms of calcium and their rough percentage of elemental calcium are:
Calcium carbonate
Calcium plus carbon and oxygen
40% elemental calcium
Commonly used products: Tums, Oral Cal Plus, egg shells (1 tsp has about 800-1,000mg of calcium)
Best taken with food because it requires stomach acid to dissolve absorb. The formulation of Oral Cal Plus helps enhance absorption without needing food.
Can be constipating. We find this a plus for whelping since loose stool or diarrhea are common after whelping.
Calcium chloride
Calcium plus chlorine (yes, it's the same chlorine element in bleach but it is NOT bleach and NOT caustic in this form)
27% elemental calcium
Commonly used product: Calsorb
Calcium citrate
Calcium plus carbon, oxygen, and hydrogen
21% elemental calcium
Commonly used product: Many human calcium dietary supplements
Easily absorbed
Calcium lactate
Calcium plus carbon, oxygen, and hydrogen
13% elemental calcium
Commonly used product: Many human calcium dietary supplements
Calcium gluconate
Calcium plus carbon, oxygen, and hydrogen 9% elemental calcium
This form is often what is given by your vet as a subcutaneous or IV injection
If you want to test the digestibility of your calcium supplement, put it in a glass of white vinegar for 30 minutes to see if it dissolves.
What about dairy products?
Most commonly, ice cream or yogurt or some other dairy product is given between puppies and thought to be sufficient. While ice cream provides a good source of energy through the sugar in it, it is surprisingly low in calcium. Here are some average calcium levels of common dairy products:
Yogurt —400 mg of elemental calcium per cup
Ice cream—200 mg of elemental calcium per cup
Cottage cheese—130 mg of elemental calcium per cup
You'll notice that dairy doesn't provide the amount we like to give per whelping. For example, a 30 lb dog would need over 13 cups of ice cream or over 6 cups of yogurt to reach the maximum amount of calcium we use.
What we use
We like Oral Cal Plus because it contains vitamin D and other ingredients that enhance calcium absorption and it's more palatable for the dogs. During whelping we want quick absorption. Some of our bitches don't like the Calsorb and will gag from it.
We use Oral Cal Plus during whelping because it's quickly absorbed and easy to give. After whelping, we switch to a bulk powdered form of calcium citrate that we mix in with her food every day. Or you can use Doc Roy's Healthy Bones tablets or granules if you want a calcium supplement with phosphorus and vitamin D. Both of these options are much less expensive than giving the Oral Cal Plus every day. The 1kg package of powdered calcium citrate for about $16 lasts us a long time. The Doc Roy's will last about 15-20 days for a 50 lb lactating bitch. We give 1.5 teaspoons of this powder to a 50 lb dog per day of lactation spread over the whelping (split between puppies) or spread over her meals during the day. Avoid giving all of the calcium in one dose as too much at once can cause heart arrhythmias or other problems.
Vitamin D helps with absorption of calcium. Ideally your dog will get enough vitamin D through her food. Vitamin D can be supplemented, but be aware that vitamin D poisoning can occur, so please ask your vet for an appropriate dose if you want to supplement vitamin D. Doc Roy's Healthy Bones tablets or granules are a good option if you want added vitamin D.
How much we give per whelping
These amounts are per whelping. Divide by the number of puppies expected and give that amount after each puppy.
Again, please always check with your reproductive vet before supplementing with calcium.
Need more help?
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References
Puerperal Hypocalcemia in Small Animals, Merck Manual Veterinary Manual
https://www.merckvetmanual.com/metabolic-disorders/disorders-of-calcium-metabolism/puerperal-hypocalcemia-in-small-animals
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