longhorn vs beef cattle

longhorn and beef cattle both are nouns.

Word	Noun	Adjective	Verb	Adverb
longhorn	Yes	No	No	No
beef cattle	Yes	No	No	No

As nouns, beef cattle is a hypernym of longhorn; that is, beef cattle is a word with a broader meaning than longhorn:

longhorn: long-horned beef cattle formerly common in southwestern United States
beef cattle: cattle that are reared for their meat

Other hypernyms of longhorn include beef.

longhorn (noun)	beef cattle (noun)
long-horned beef cattle formerly common in southwestern United States	cattle that are reared for their meat