milk cow vs dairy cattle

milk cow and dairy cattle both are nouns.

Word	Noun	Adjective	Verb	Adverb
milk cow	Yes	No	No	No
dairy cattle	Yes	No	No	No

As nouns, milk cow and dairy cattle are synonyms defined as:

Other synonyms of milk cow include dairy cow, milch cow, milcher, milker.

milk cow (noun)	dairy cattle (noun)
cattle that are reared for their milk	cattle that are reared for their milk