The Spanish word for hay as in the dried grass fed to horses is heno. You can say “heno para caballos” for “hay for horses”.

Quick note

  • heno = hay, the dried grass used as animal feed.
  • hay in Spanish is a different word and usually means there is / there are.

Example

  • Necesito comprar heno para mis caballos.
    “I need to buy hay for my horses.”

If you want, I can also give you the Spanish word for straw and feed so you can compare them.