How rotted does manure have to be for pumpkins and squash?

I'm going to be planting up a bed of around 7 diff squash and pumpkins, and wondered whether the "free manure"  (it'll be horse poo) on offer in the local Friday Ad would be ok to use in the planting holes? I know people say that you should leave manure to rot for ages before digging it in, but thought squashes might be hardy enough.

My compost is looking pretty un-rotted in its bins, which has scuppered that plan (I used up the rotted stuff in the spring).

We found this out the hard way  afew years back when we spread manure from the farm around our pumpkin plants and the stems went all black