The animals throw certain objects into the well because they symbolize?

The items thrown into the well or burned were symbolic of Jones' reign over the farm. All were items of oppression and all were destroyed.

The harness-room at the end of the stables was broken open; the bits, the nose-rings, the dog-chains, the cruel knives with which Mr. Jones had been used to castrate the pigs and lambs, were all flung down the well.