"And then, after a few preliminary tries, the whole farm burst out into "Beasts of England" in tremendous 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."
The animals now have something to take pride in and work together for a greater cause than self preservation. They are now proud of what they can and will accomplish together. This is why the rebellion of animal farm happened, the animals finally had something to band together for.