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A horse's diet should have at least as much calcium as phosphorus. What is the minimum calcium to phosphorus ratio?

1:1 minimum, with about 2:1 ideal.

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  1. 1:2, more phosphorus
  2. 1:1 ✔
  3. 6:1

Why: Calcium and phosphorus build bones, and the balance matters as much as the amounts. Too much phosphorus can pull calcium away from bone. Grain is high in phosphorus, so hay and balancers help.

Huh, didn't know that: UMN notes that soil in many parts of the US is low in selenium, so hay grown there can be low in it too.

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References

Answer: 1:1. Calcium and phosphorus build bones, and the balance matters as much as the amounts. Too much phosphorus can pull calcium away from bone. Grain is high in phosphorus, so hay and balancers help.

  1. Feeding a mature horse, UMN Extension extension.umn.edu/node/5556
    horses require a minimum Ca:P ratio of 1:1 and an ideal Ca:P ratio of 2:1.
    Checked 2026-10-10.
  2. Ten things you should know about feeding the mature horse, UMN Extension extension.umn.edu/horse-nutrition/ten-things-you-should-know-about-feeding-mature-horse
    Balance your horse's ration in this order: energy, protein, minerals, vitamins.
    Checked 2026-10-10.
  3. Ten things you should know about feeding the mature horse, UMN Extension extension.umn.edu/horse-nutrition/ten-things-you-should-know-about-feeding-mature-horse
    in many areas of the country, the soil is deficient in selenium.
    Checked 2026-10-10.

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