An animal that is one year old called what?

There isn't a single word for an animal that is one year old. The term used depends on the specific animal:

* For most mammals: "Yearling" is often used, but it can also be used for other young animals.

* For cattle: "Yearling" is the common term.

* For horses: "Yearling" is the standard term.

* For dogs and cats: "Puppy" and "kitten" are used for animals under a year old, regardless of whether they are exactly one year old.

* For birds: "Fledgling" is used for young birds that have recently left the nest.

So, it's important to specify the animal when asking about its age. For example, "A one-year-old horse is called a yearling."