beast of burden vs work animal

beast of burden and work animal both are nouns.

Word	Noun	Adjective	Verb	Adverb
beast of burden	Yes	No	No	No
work animal	Yes	No	No	No

As nouns, work animal is a hypernym of beast of burden; that is, work animal is a word with a broader meaning than beast of burden:

beast of burden: an animal such as a donkey or ox or elephant used for transporting loads or doing other heavy work
work animal: an animal trained for and used for heavy labor

beast of burden (noun)	work animal (noun)
an animal such as a donkey or ox or elephant used for transporting loads or doing other heavy work	an animal trained for and used for heavy labor