Use of the Cow in Siegecraft

Rabelais, Gargantua and Pantagruel II.15 (tr. J.M. Cohen):

On their return Panurge considered the walls of Paris, and said to Pantagruel in derision: 'Oh, how strong they are! They're just the thing for keeping goslings in a coop. By my beard, they are pretty poor defences for a city like this. Why a cow could knock down more than twelve foot of them with a single fart.'