What smelly event occurred as a result of Avery's actions? How did it happen?

Avery and Fern have been spending a carefree, fun day at the Zuckermans' farm. They take turns to play on the swing, go picking berries, and eat some of Mrs. Zuckerman's blueberry pie. But Avery is seldom very far from getting into mischief of one sort or another, and today is no different. For the first time, he sees Charlotte sitting in her web. Avery finds himself fascinated by the little creature. He decides that he's going to keep her all for himself. So standing on a stool, he approaches Charlotte's web and tries to knock her into his box using a stick.
Thankfully, Avery's foolish idea gets the comeuppance it deserves. He loses his balance on the stool, and in his fall he tips over Wilbur's trough. This in turn breaks a rotten goose egg, which apparently was sitting underneath the trough. When the egg breaks, it gives off the most revolting smell imaginable. Indeed, the smell is so bad that Fern and Avery have no choice but to run away from the barn as quickly as possible. Charlotte has just had a very lucky escape indeed.