I believe all of them sang the song. The song rouses the animals, even the dullest of whom learn it in minutes. In fact, the animals are so taken with the song that they sing it five times in unison.
The cows lowed it, the dogs whined it, the sheep bleated it, the horses whinnied it, the ducks quacked it. They were so delighted with the song that they sang it right through five times in succession, and might have continued singing it all night if they had not been interrupted.