I thought "cattle" was an irregular plural of cows, as in you couldn't say "a cattle of cows".
But otherwise I agree with Jackdaw, and it depends on context. Easier for me I think to demonstrate with a different word with the same properties: compare "The team is second in the league" v. "The team are wearing red shirts". In the first case, the "team" is one collective unit (as opposed to other teams), but in the second case, the "team" is really just eleven players, so should be seen in a plural sense.