Strange blood worm

I came across some of these strange small what look like blood worms in a big bile of well rotted horse manure that was for free and i was wondering if these are a bad or good sign before i load up with some
cheers
PP. 

theres masses of them like chicken chow mein
and i dont want to be eating chines any time soon thanks to my description 

Brilliant thanks sunshineband ill be down the stables asap