calcium carbonate

What it is

Calcium carbonate — and yes, 'ground limestone' on a label means exactly that. Before the word alarms you: it's the same substance as human antacid tablets and calcium supplements, quarried instead of synthesized. Purity specifications, not provenance, decide feed quality.

Why it's in pet food

Meeting the calcium requirement and balancing the calcium-to-phosphorus ratio, which matters as much as either number alone. Meat is phosphorus-rich and calcium-poor; something must close the gap, and limestone closes it for pennies.

How Bowlmark scores it

Scores are deterministic math over the printed label — the rules below apply to every product identically, and nothing estimates or fills in a blank.

Neutral — the engine scores no mineral supplement in either direction, because adequacy lives in the formulation, not the ingredient wording. The safety note pets actually need: calcium is where home supplementation goes wrong fastest. Growing large-breed puppies are harmed by EXCESS calcium (developmental orthopedic disease), which is why large-breed-puppy formulas control it tightly — never add calcium to a complete diet, especially a puppy's.

Read the full methodology

Foods that list calcium carbonate

Ranked by score where scores exist. Placement here is never sold.

• Kettle Creek Farmhouse Chicken & Sweet Potato94
• Meadow Farms Chicken & Oatmeal Puppy93
• Open Farm Large Breed Grain-Free RawMix93
• Open Farm Large Breed RawMix with Ancient Grains93
• Open Farm Small Breed Chicken & Turkey Recipe93
• Open Farm Wild-Caught Salmon Dry Cat Food93
• Copper Hollow Lamb & Brown Rice Sensitive Skin & Stomach92
• Fernbrook Kitchens Heritage Rabbit Single-Protein Pâté92

Sources

• AAFCO large-size-dog growth calcium provisions
• NRC Nutrient Requirements of Dogs and Cats (2006)

Related ingredients

• calcium iodate
• copper proteinate
• copper sulfate
• zinc oxide
• zinc proteinate
• zinc sulfate

Further reading

• The guaranteed analysis, decoded
• How to read a pet food label