The Importance of Calcium Supplements in Homemade Cat Food

The Importance of Calcium Supplements in Homemade Cat Food

Many of you already know that calcium is without a doubt one of the most important nutrients in a cat's diet. It forms healthy bones and teeth, helps in blood clotting, muscle function, nerve transmission and membrane permeability.¹

While some diets like whole prey, frankenprey, sometimes called BARF or bones and raw food, or ground meat with bone generally do not require any calcium supplementation, it is very important to add calcium supplements to all boneless meat diets. Feeding meat without bones and without another source of calcium can be disastrous for a cat. It can lead to decreased growth, bone mineralization, decreased appetite, lameness, spontaneous fractures, loose teeth, tetany, convulsions and rickets.² Some of these conditions can become irreversible or even fatal.
So what would be the best calcium supplement for home-prepared boneless cat food? There are a few choices, so here are the pros and cons for each:

Calcium carbonate (CaCO3)

It is mostly used as ground mineral limestone or eggshell powder. I have to admit that this is my favorite calcium supplement for boneless meat. Pros: It has no taste or odor and it can be very low in heavy metals. Another advantage is that it has no phosphorus. That makes it an ideal balancing ingredient for boneless meat which is naturally low in calcium and high in phosphorus. You can also easily make your own eggshell powder if you have a good source of eggshells available. All you have to do is to rinse the eggshells well and bake them approximately 10 minutes at 300 degrees F. Then grind them to make the eggshell powder. See the recipe article for tips on making your own eggshell powder. Cons: None.
Bone meal (calcium hydroxylapatite Ca10(PO4)6(OH)2)

Pros: A great natural source of calcium, phosphorus and other nutrients. Bone meal can be made at home as a safer option to store-bought products. Cons: Difficult or in some cases impossible to get the right calcium/phosphorus ratio in meat and bone diets. See more about Ca:P ratio below. Bones can be contaminated with heavy metals as many commercial bone meal products are made from older animals. This increases the possibility that the bones have accumulated heavy metals. Note: Do not use bone meal from home or garden stores. These are not intended for consumption and may contain toxic fertilizers.
Calcium bound to lactate, citrate, ascorbate, and other organic acids

Pros: Might be more easily and completely absorbed than other calcium supplements, such as calcium carbonate or bones. Cons: Might have an off taste and all of these supplements are synthetic, not natural.
Let's take a few steps back for a moment and talk about calcium/phosphorus ratio. Using diets with the correct calcium to phosphorus (Ca:P) ratio is essential for proper bone development and maintenance. There are many different opinions on what the ideal Ca:P ratio should be but I think it is reasonable to recommend a range between 1.0 to 1.3 parts of calcium per 1 part of phosphorus. Unfortunately, it might be very challenging to get within this range with some whole prey or BARF diets. Besides, bones can provide significant levels of calcium and phosphorus in addition to the phosphorus in meat and these diets usually end up with high levels of both calcium and phosphorus which might be just fine for younger cats, but not so great for older cats.
Fortunately, it is easy to calculate accurate Ca:P ratios in calcium supplemented boneless diets. To reach the above recommended range, you would need to add 1000 mg of elemental calcium (approximately 3 grams of eggshell powder) to 1 pound of raw boneless meat. Please contact me if you want more details regarding this calculation.
Editor's note: Many of you will want to know how much 3 grams of eggshell powder is in teaspoons. We don't give it that way here for two reasons. Three grams will measure differently depending on how finely ground the powder is and whether it is freely scooped or packed. It may be less convenient to weigh it, but it is more accurate.
Finally, a couple of suggestions:
Avoid calcium supplements that contain added vitamin D. Do not over supplement. Too much calcium can cause health problems. Other key minerals, like iron, magnesium and zinc can become depleted in the body when a pet is consuming too much calcium. Excess bone consumption may cause problems leading to stomach discomfort, vomiting or fever. If that happens, please contact your veterinarian.
Note: Feline Nutrition provides feline health and nutrition information as a public service. Diagnosis and treatment of specific conditions should always be in consultation with your own veterinarian. Feline Nutrition disclaims all warranties and liability related to the veterinary advice and information provided on this site.

Marta Kaspar holds a master's degree in chemistry from the University of Pardubice in the Czech Republic. She is a research scientist, and a formulation and analytical chemist in both industrial and academic fields. Marta became interested in feline nutrition when her cats developed health problems. When she decided to prepare their food herself, the effect of the homemade raw meat diet on her cats was so impressive that she created the line of Alnutrin® supplements to help others transition their cats to better diets. You can find her at
 1. MS Hand DVM, PhD, CD Thatcher, DVM, MS, PhD, RL Remillard, PhD, DVM and P Roudebush, DVM, Small Animal Clinical Nutrition, 4th ed. Walsworth Publishing Company, 2000, pg 71.
  2. Karen J. Wedekind, Shiguang Yu, Inke Paetau-Robinson, Christopher S. Cowell, Lauren Kats; Small Animal Clinical Nutrition, 4th ed. Walsworth Publishing Company, 2000, Chapter 6, pg 108.
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