How do you call an old horse?

There isn't one specific term for an old horse. Here are a few options, depending on the context:

Formal:

* Senior horse: This is the most neutral and respectful term.

* Geriatric horse: This term is often used in a veterinary context.

Informal:

* Old timer: This is a common and affectionate term.

* Veteran: This implies respect for the horse's long life and service.

* Grandfather/Grandmother: This is used for horses that have lived a long time and may have offspring.

You could also use the horse's name with a descriptor like "old" or "elderly" depending on the situation.

It's important to remember that horses age differently than humans. A 20-year-old horse is considered quite old, while a 30-year-old horse is truly a senior citizen.