dairy cow vs dairy cattle

dairy cow and dairy cattle both are nouns.

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

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

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

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