English: Round bale silage, Thornton. Silage making in the bale. The plastic wrapping provides the airtight conditions for the fermentation of the grass to take place. The finished silage is portable and can easily be transported to the animals. A problem is that the bags can be punctured easily, fox cubs playing is one culprit. The original big black polythene bags have been replaced by more durable coverings. Sadly these coverings are a bit of an environmental problem, in that they are hard to dispose of. I used to burn ours, but that practice has since been made illegal.