Balancing Calcium In Homemade Dog Foods

calcium in dogs

Calcium is the most abundant mineral in your dog’s body. In fact, a 75 lb dog houses about a pound of calcium. Clearly, it’s an important mineral! But many raw and cooked foods get calcium wrong. And there are other minerals that support calcium that also need to be balanced.

This sounds complicated, and it can be! But we’ll break it down for you and make it easy for your dog to get the right amount of calcium (and other minerals too).

The Role Of Calcium In Dogs

About 99% of the calcium in your dog is stored in his bones. Along with phosphorus, calcium is critical for skeletal health so it’s important for dogs to get enough in their diets. The remaining calcium is mainly found in the blood and lymphatic system where it plays a role in hormone function, cell structure, enzyme activity, cardiovascular and immune function.

Calcium acts as a messenger that allows cells to respond to hormones and neurotransmitters. Neurotransmitters are found at the ends of nerves and they release calcium ions into the muscles and this influx of calcium causes the muscle to contract. In fact, rigor mortis happens because of calcium … after death, the muscle cell membranes become more permeable and allow more calcium in. Normally, ATP (adenosine triphosphate) works alongside calcium and is used to relax the muscles, but ATP is a byproduct of metabolism and the dead can’t produce energy. So the excess calcium causes the muscle contractions you see in rigor mortis.

Of course, rigor mortis is the ultimate calcium malfunction … but it shows the importance of keeping calcium levels within a very small range. If there’s too little or too much, your dog could develop seizures, loss of muscle control … and eventually death.

Low Calcium Levels In Dogs (Hypocalcemia)

If your dog’s food doesn’t have enough calcium, the parathyroid hormone will pull calcium out of his bones to keep circulating levels of calcium up. After weeks or months of this, you’ll start to see skeletal issues, such as rickets and bone loss. The typical signs you’ll see in your dog include stiffness, muscle twitching, limping and bone pain.

Insufficient calcium is much more sinister in puppies than in adult dogs. Puppies require more calcium to support their bone growth. Too little calcium in the puppy’s diet can cause osteochondritis dissecans (OCD), hypertrophic osteodystrophy (HOD), hip and elbow dysplasia and panosteitis. These issues can also happen if the ratio of calcium to phosphorus is out of balance.

Nutritional Secondary Hyperparathyroidism

Insufficient calcium in the diet can cause a condition called nutritional secondary hyperparathyroidism … especially if there’s a large amount of phosphorus and too little vitamin D in the diet. Nutritional secondary hyperparathyroidism happens when too much parathyroid hormone is produced and too much calcium is pulled from the bones. This weakens the bone (this is called osteopenia) and you’ll see neurological signs related to low blood calcium, such as muscle twitching and seizures. In most cases, nutritional secondary hyperparathyroidism can be treated with proper levels of calcium and phosphorus.

Too Much Calcium (Hypercalcemia)

Hypercalcemia is too much calcium in the blood. While the parathyroid hormone releases calcium from bone when there’s too little calcium, the hormone calcitonin removes calcium from the blood and sends it into the bones. Most adult dogs can deal with large amounts of calcium in the diet … apart from constipation, they should have little trouble maintaining blood calcium levels. But puppies aren’t able to balance calcium as well as adults. Too much calcium can cause joint and skeletal issues, especially if the calcium isn’t balanced with phosphorus, other minerals and vitamin D.

If you’re feeding your dog or puppy a balanced diet for all life stages, then there should be enough calcium in the food … and it will probably be correctly balanced with phosphorus. But don’t just assume it does … the food must say “Complete and Balanced” on the label, otherwise the minerals may not be balanced. Foods have to meet minimum nutritional requirements set by the Association of Feed Control Officials (AAFCO) before they can claim Complete and Balanced on the label.

Adding calcium supplements to complete and balanced foods, especially for puppies, should be avoided since they’re already balanced. If you’re feeding your dog a home cooked or home prepared raw diet, you’ll need to add calcium to his meals. Let’s look at the different sources of calcium and how much to give your dog.

How Much Calcium Do Dogs And Puppies Need?

If you want to get calcium right, you also need to get phosphorus right. Both minerals are tightly regulated in the body by the parathyroid hormone and vitamin D. Calcium needs to first be combined with phosphorus before it’s stored in bones … so just as too little calcium can cause skeletal issues in dogs, so can too little phosphorus. Calcium and phosphorus combine to give bones their structure and strength.

If there’s too much phosphorus in the diet, calcium will be pulled from the bones to balance out the blood levels of phosphorus. So too much phosphorus in the diet will also weaken bones and cause calcium deposits in soft tissue. So when you’re adding calcium to homemade diets, you have to pay attention to both calcium and phosphorus. Here are three things you need to consider:

  1. How much calcium is in the food?
  2. How much phosphorus is in the food?
  3. What is the ratio of calcium to phosphorus?

AAFCO Calcium Requirements

AAFCO has set minimum and maximum requirements for the amount of both calcium and phosphorus in dog foods. We can also use AAFCO requirements to make sure our homemade diets have the right balance of calcium and phosphorus. Because puppies need larger amounts of calcium, there are different requirements for dogs and puppies:

Min CalciumMax CalciumMin PhosphorusMax PhosphorusMin Ca:PMax Ca:P
1.25 g / 1,000 kcal6.25 g / 1,000kcal1 g / 1,000kcal4 g / 1,000kcal1:12:1
AAFCO/NRC Calcium and Phosphorus For Adult Dogs
Min CalciumMax CalciumMin PhosphorusMax PhosphorusMin Ca:PMax Ca:P
3 g / 1,000 kcal6.25 g / 1,000kcal2.5 g / 1,000kcal4 g / 1,000kcal1:12:1
AAFCO/NRC Calcium and Phosphorus For Growth & Reproduction

Meat is very rich in phosphorus and contains very little calcium. On the other hand, bones are rich in both calcium and phosphorus with a Ca:P ratio that averages about 2:1. So an all-meat diet will be deficient in calcium and you need to add calcium in some form.

Many raw feeders add bone to their meals to balance the Ca:Ph ratio … but many raw fed dogs can’t eat bone. Senior dogs, dogs with poor teeth, small dogs and puppies can find it difficult to consume bone, putting them at risk for calcium deficiency. Plus, bones can splinter or break teeth. So many raw feeders add a different source of calcium to their foods.

Cooked foods can’t contain bones because bones must be fed raw. So cooked diets always need a source of calcium. So let’s take a look at calcium sources you can add to raw and cooked meals.

RELATED: How to make sure your do gets enough calcium from bones …

Calcium Supplements And Sources

There are several sources of calcium you can add to your dog’s food … but they’re not all the same and they’re not all suitable for puppies. The most common calcium supplements and foods you can add include:

  1. Eggshells
  2. Coral calcium
  3. Seaweed calcium
  4. Bone meal

Each calcium source has different amounts of minerals. Here’s the breakdown in dry matter:

Calcium SourceCalciumPhosphorusCa:PMagnesium
Egg Shells33.7%0%0
Coral Calcium34%0.1%425:12.4%
Seaweed Calcium34.2%0.8%41.7:13.42%
Bone Meal19.3%9.3%2.1:12.46%
Bone15.6%2.9%2:10.11%
Nutrients (Dry Matter)

Of course, real bone is the gold standard when it comes to supplementing calcium. It has a Ca:Ph ratio of 2:1 so it contains a good amount of phosphorus and also contains magnesium and vitamin D. In comparison, seaweed and coral calcium contain very little phosphorus. And eggshells are drastically different from bone with no measurable amount of phosphorus or magnesium. This makes eggshells a fairly unnatural alternative to bone.

Let’s look at each source of calcium next and how much you need to add to your dog’s meals.

Adding Calcium To Homemade Foods

Kibble and most commercial pet foods are formulated on a dry matter basis (how much of a nutrient remains when the water weight of the food is removed). This works well for kibble because most kibble is the same … but raw and home cooked diets need to be formulated on a caloric basis because they contain a wide variety of calories from fat. Simply stated, this means “How much calcium is in 1,000 calories of food?”

Now, it would be simple and easy to say “Add 1 teaspoon of calcium supplement to 1 pound of food” … but fat contains twice as many calories per pound as protein and carbohydrate. This means the amount of food your dog eats every day depends on the fat content. So fresh diets need to be analyzed by calories, not dry matter.

With that said, here’s a breakdown of each calcium source and how well it will balance diets with various fat levels. We don’t recommend feeding a diet that’s over 20% fat … this would contain twice as much fat as protein and is not recommended for long-term health. Fat is relatively devoid of vitamins and minerals, so it’s important to feed no more than 20% fat without veterinary guidance. This is especially important for puppies and pregnant dogs because they will not be able to get enough nutrition from their food unless they eat too many calories. Remember, much of your dog’s meal is water weight, so a food that’s 20% fat will only contain about 10% protein. Ideally, you’ll want to feed 10% fat and certainly no more than 15% fat.

Egg Shells As A Source Of Calcium

While many home made diets use egg shells as a source of calcium, they’re deficient in other minerals. The amount to feed is about 1 teaspoon per pound of food, which is about 5 grams. Here’s how calcium balances the minerals in foods for adult dogs. As you can see, egg shells can only be used with very lean meats. If you feed more than 10% fat (including any oils you add to the food), your dog will not get enough phosphorus.

Adult Dogs

1 teaspoon Eggshell Powder (5 g) Added To 1 Pound Food:CalciumPhosphorusCa:P
10% Fat (90% Lean)2.351.192:1
15% Fat (85% Lean)1.910.892.2:1
20% Fat (80% Lean)1.610.692.4:1
AAFCO Adult Minimum Requirements1.251.001:1
AAFCO Maximum Requirements6.254.002:1
Amount per 1,000 kcal

Puppies & Pregnant/Nursing Dogs

Puppies need nearly double the amount of calcium as adult dogs. So if you double the amount of egg shells, there’s enough calcium in the diet. But because egg shells only contain calcium, it still won’t meet minimum AAFCO requirements for phosphorus. So eggshell powder is not recommended for growth and reproduction.

2 teaspoon Eggshell Powder (10 g) Added To 1 Pound Food:CalciumPhosphorusCa:P
10% Fat (90% Lean)4.621.192:1
AAFCO Puppy Minimum Requirements3.002.501:1
AAFCO Maximum Requirements6.254.002:1
Amount per 1,000 kcal. Minerals in red do not meet requirements.

Coral Calcium

Like egg shells, coral calcium is also extremely high in calcium but relatively low in phosphorus. This also makes coral calcium a poor choice for adult dogs eating a moderate to high fat diet. If you choose coral calcium as a calcium source, you need to make sure your dog’s meals are very lean or there can be a mineral imbalance and phosphorus deficiency. Feed 3/4 teaspoon per pound of food that’s no more than 10% fat. Any food that contains more than 10% fat will cause a phosphorus deficiency.

Adult Dogs

3/4 teaspoon Coral Calcium Powder (3.6 g) Added To 1 Pound Food:CalciumPhosphorusCa:P
10% Fat (90% Lean)1.791.171.5:1
15% Fat (85% Lean)1.460.881.7:1
20% Fat (80% Lean)1.240.71.8:1
AAFCO Adult Minimum Requirements1.251.001:1
AAFCO Maximum Requirements6.254.002:1
Amount per 1,000 kcal. Minerals in red do not meet requirements.

Puppies & Pregnant/Nursing Dogs

Puppies would need a larger amount of coral calcium to meeting AAFCO minimum requirements. But doubling the amount of coral calcium doesn’t raise phosphorus levels enough to properly balance the minerals. So coral calcium should not be fed to puppies and pregnant or nursing dams.

1 1/2 teaspoon Coral Calcium Powder (7.2 g) Added To 1 Pound Food:CalciumPhosphorusCa:P
10% Fat (90% Lean)3.441.162.9:1
AAFCO Growth & Reproduction Minimum Requirements3.002.501:1
AAFCO Maximum Requirements6.254.002:1
Amount per 1,000 kcal. Minerals in red do not meet requirements.

Seaweed Calcium

Seaweed calcium is another calcium source that’s high in calcium and low in phosphorus. This also makes it a bit tricky to use with anything but very lean meats. Like coral calcium, adding more seaweed calcium won’t help balance the minerals because there will still be too little phosphorus. Feed 1 teaspoon per pound of food that’s no more than 10% fat.

Adult Dogs

1 teaspoon Seaweed Calcium Powder (3 g) Added To 1 Pound Food:CalciumPhosphorusCa:P
10% Fat (90% Lean)1.501.221.2:1
15% Fat (85% Lean)1.220.911.3:1
20% Fat (80% Lean)1.030.711.5:1
AAFCO Adult Minimum Requirements1.251.001:1
AAFCO Puppy Minimum Requirements3.002.501:1
AAFCO Maximum Requirements6.254.002:1
Amount per 1,000 kcal. Minerals in red do not meet requirements.

Puppies & Pregnant/Nursing Dogs

You would have to add 3 teaspoons of seaweed calcium to meet the minimum calcium requirements for growth and reproduction. But this doesn’t provide enough phosphorus and the Ca:Ph ratio doesn’t meet AAFCO requirements. So seaweed calcium is not recommended for growth and reproduction.

3 teaspoon Seaweed Calcium Powder (9 g) Added To 1 Pound Food:CalciumPhosphorusCa:P
10% Fat (90% Lean)4.341.293.4:1
AAFCO Puppy Minimum Requirements3.002.501:1
AAFCO Maximum Requirements6.254.002:1
Amount per 1,000 kcal. Minerals in red do not meet requirements.

Bone Meal

Bone meal is bone that’s been dried, either with or without heat. Minerals are pretty resistant to heat, so it’s generally safe to heat and powder bones. But you can also find higher quality sources of bone meal that hasn’t been heat treated, which would be preferred.

The benefit of bone meal over other sources of calcium is that there’s much less risk of mineral imbalance. Bone meal will almost always give you the proper ratio of calcium and phosphorus, just as real bones will. Feed about 2 teaspoons per pound of food to adult dogs.

Adult Dogs

2 teaspoons Bone Meal Powder (8 g) Added To 1 Pound Food:CalciumPhosphorusCa:P
10% Fat (90% Lean)2.122.151:1
15% Fat (85% Lean)1.721.671:1
20% Fat (80% Lean)1.461.341.1:1
AAFCO Adult Minimum Requirements1.251.001:1
AAFCO Maximum Requirements6.254.002:1
Amount per 1,000 kcal.

Puppies & Pregnant/Nursing Dogs

Apart from fresh bones, bone meal is the only source of calcium that should be fed to puppies and pregnant dogs. Because it contains both calcium and phosphorus in the right ratio, larger amounts will deliver enough calcium without creating the imbalance between calcium and phosphorus seen with the other calcium sources. The amount to feed is about 4 teaspoons per pound of food for meals that are 10% fat. If feeding 15% fat, then there won’t be quite enough phosphorus, so feed 5 teaspoons. If there is 20% fat or more (more than 20% fat is not recommended for puppies), then increase the amount to 6 teaspoons.

4 teaspoons Bone Meal Powder (16 g) Added To 1 Pound Food:CalciumPhosphorusCa:P
10% Fat (90% Lean) – Add 16 g Bone Meal or 4 tsp4.093.091.3:1
15% Fat (85% Lean) – Add 20 g Bone Meal or 5 tsp4.122.811.5:1
20% Fat (80% Lean) – Add 24 g Bone Meal or 6 tsp4.132.621.6:1
AAFCO Puppy Minimum Requirements3.002.501:1
AAFCO Maximum Requirements6.254.002:1
Amount per 1,000 kcal.

Toxins And Heavy Metals In Calcium Supplements

Whichever source of calcium you choose for your dog, it’s important to be aware of potentially harmful substances they might contain. Let’s look at each calcium source and the potential problems with each:

Egg Shells
Many eggs are coated in a waxy, chemical cleaner, which is toxic to your dog. We don’t recommend egg shells as a source of calcium but if you use them, buy them from a local farmer who washed the eggs with water only. Grocery store eggs will likely have contaminated shells.

Coral and Seaweed Calcium
Both these forms of calcium come from the ocean and are often high in heavy metals like mercury, PCBs and dioxins. It’s important that your source of sea calcium is tested low in these toxic substances.

Bone Meal
Bone meal can be a source of lead and glyphosate. Make sure your bone meal comes from young animals and is tested low in lead, pesticides, herbicides and other heavy metals.

What’s The Best Source Of Calcium For Dogs?

The farther you stray from Mother Nature, the more can go wrong. That’s why bones are always the best source of calcium for dogs. They have the right balance of calcium and phosphorus and will balance all meals, even for puppies. This includes bone meal, as long as it’s high quality and tested for heavy metals. We recommend Better Bones from Four Leaf Rover. It’s air-dried bones sourced from pastured young cattle from Australia. Every batch is also third-party tested for metals and pesticides. Alternatively, look for calcium hydroxyapatite that’s third-party tested for safety.

Egg shells, seaweed and coral calcium are all rich in calcium but very low in phosphorus. This means they should not be fed to puppies or pregnant/nursing dams. If using these as a calcium supplement for adult dogs, they will only balance foods that are 10% fat or less (remember, your oils will increase the fat content if you add them to your dog’s meals). If your food contains more fat, then you either need to feed too much calcium or too much phosphorus so it’s important to stick to lean foods.

There are other sources of calcium, including dicalcium phosphate, calcium citrate, calcium carbonate or calcium proteinate. These are the forms of calcium added to dog foods … but you’re probably feeding raw or home cooking to give your dog a higher quality diet than kibble and commercial foods. So we don’t recommend chemical minerals made in a lab … we always prefer food-based nutrition over synthetic nutrition.

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