Donkeys eat my compost heap

Photo taken a few days ago. The grass in the field had gone sour so the donkeys preferred to lean over the wall and munch the leaves and grass clippings on my compost heap.

I'm not entirely sure what is meant by sour. It seems to mean more than weedy (though weedy it certainly was). I think it means that the donkeys have fouled it, and being fatstidious animals (unlike cows) they then refuse to eat it.

The field has now been topped - mown with the mower at a high setting, with the cuttings left to melt back in. This will encourage tasty fresh growth, after which my compost heap will become less appealing.