work animal vs brute

work animal and brute both are nouns.

Word	Noun	Adjective	Verb	Adverb
work animal	Yes	No	No	No
brute	Yes	Yes	No	No

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

Other hypernyms of work animal include animal, animate being, beast, creature, fauna.

work animal (noun)	brute (noun)
an animal trained for and used for heavy labor	a living organism characterized by voluntary movement
	a cruelly rapacious person

work animal (adjective)	brute (adjective)
	resembling a beast; showing lack of human sensibility