Back to my original post, I hit google and just read a couple of studies of the effect of Ivermectin (de-wormer) etc on decomposition of cow pats. One of the studies concentrated on earthworm activity.

Both studies found no difference.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1831547/

2nd Article


However I also found one study that said dung fauna and dung degradation was reduced.
http://www.springerlink.com/content/387363451x5k227w/

If the same holds for horse manure, then it's looking good for worms.

It has been said previously that by the time the manure leaves the horse the poison is neutralizedt err is human but why kill your worm due to a mistake let it sit for a week or two.

When I first get it, I flood it a bit with water to wash out any urine, and this tends to kill the smell just about straight away.

I then let it sit for about 2 weeks, turning and adding water every couple of days.

After about a week I put some in a small container with 10 worms which I then check every couple of days before eventually using the manure in my flow through wheelie bin.

So far so good, and I see no reason to change this practice, but it's nice to know that research has been done. It had bothered me that perhaps the de-wormers were slow release and the carnage might not show up for a while.

Your asking for the truth, but all I can give is personal experience.
As far as I know there are no scientific studies showing good or bad results.
In my experience, Cymbidium do very well potted in Horse manure, given my growing conditions.
I have also found that Phaius tankervilliae does good under the same conditions.
Notice I didn't say very well because I am not as impressed with the results so far.
I suggest you try it yourself on a division that you have no concern with killing and see what happens.
Its all about experimenting and learning so enjoy.

Just an update.

We are having a mild summer so far, but the bin is working so well I recently built another one, the differences being no chimney (no idea if it helps or not) and that I used steel ceiling hanging rods instead of the threaded rods.

The new bin is still filling, but the original is delivering around 4-6 litres a day of vermi-compost just dropping into the bottom area.

I use a spade to collect it, then sort through to get the worms back and either use it on the garden or put it in bags as I am collecting to be able to plan more vegetables shortly.

I have rarely scraped the bottom to get castings to drop, it's been happening all by itself mostly.