Horse muck

Personally we prefer with straw.  Helps with the break down we found.

I doubt that anyone would take straw out of manure.  It is much more likely that it was never in there.  Possibly it is not actually taken from stables, but 'poo picked' from fields where horses are grazed.  This would not be so good because it will not contain nitrogenous urine which helps with the breakdown.

Horses are now bedded in all kind of things, mainly because straw often contains fungal spores which can cause health problems.  Wood shavings, shredded paper or hemp can be used.  Any manure is better than none.