dairy cattle vs dairy cow

dairy cattle and dairy cow both are nouns.

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

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

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

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