Η αγελάδα δίνει γάλα.

English Translation

Cows supply milk.

The Greek is “The cow supplies milk” not cows.
To provide the English here is a possible Greek sentence
“οι αγελάδες παρέχουν γάλα” or “οι αγελάδες δίνουν γάλα”

This sentence was added to Tatoeba by a native speaker and I believe it is simply idiomatic. In English we tend to say ‘cows give milk’, but in Greek I think the singular is more common. We can do this in English too - ‘The cow (as a species) gives milk’.

Thanks AmyJean for taking time to respond.