Hydroxyproline

Hydroxyproline is an amino acid that occurs in the body almost exclusively in cartilage protein, where it accounts for between 12 and 14%. Together with the amino acid proline and glycine, they make up a good 50% of collagen. Collagen, in turn, is a protein found in connective tissue, cartilage, tendons, ligaments and bones, giving them structure and stability.

If you want to feed horses the three important amino acids for support, you need to use gelatine or collagen hydrolysate.