Any on here using horse manure and having bad results?
If straw-based it may have traces of selective weedkiller.
Is that what you meant?
I prefer the wood-shavings bedding, doesn't smell unpleasant and is far easier to handle, makes a nice mulch. Also is a good source of slightly used bailer twine and slow-worms.

Any on here using horse manure and having bad results?