HG came close to the point I'd like to make...
Many of these studies do not specify the maximum temperatures which were achieved, nor for how long those temps were maintained, to produce the results discussed, whether regarding E. coli or other pathogens.
On the whole, I trust the composting process to take care of lots of nasty stuff. But there's a lot I won't put into my own BioStack because I know that *my* compost runs cold (less than 95 deg). If it were to achieve the high temps that many compost operations do (135 or higher), I could be more flexible about what went into it. *sigh* But, in the interest of safety, I send my weeds to a commercial operation in my yard waste.
And that's a lot of biomass.
Feedlots are indeed a very large source of E. coli. Where have those ground-meat recalls originated? In industrial meat factories, where the meat from hundreds of animals, slaughtered together in CAFOs, was ground together in (proved) unsanitary conditions.
I'm not a vegetarian, but to me these recalls say, "Know where your food comes from."
There was a problem maybe two years ago in the UK w/regard to horse manure--and this was a major scandal, given the love for gardening in the UK and the allotment system. An herbicide had been applied to many meadows whose hay was fed to horses. It didn't have an ill effect on the horses, but when the horses' manure was applied and allowed to stand on allotments over the winter, plants sickened and died the next spring. (I'll have to go find a citation to back this up....) I don't think said herbicide was ever used on this side of the Atlantic, but again, ask your source/stable whether the horses are on antibiotics, wormers, etc.
Sunset Zone 17, USDA Zone 9