Oh My god. I have to say.. Im not sure what the State laws on these kind of things are, but in Alabama if the body hasn't been disposed of in like, 12 hours, the county can shut the operation down. Not only do i find what you said about the horse being left for at least 24 hours disgusting, but it also -deeply- disturbs me because of how disrespectful it is to the deceased and the old owner, as well as to the boarders. I swear, 80 jillion red flags just popped up over my head when i read that. I hope to God the stalls on either side of that horse were kept empty. I would be -thoroughly- offended if i was still boarding my horse somewhere and the Barn Owner thought it was OK to keep my horse next to a dead one. Thats completely unacceptable. There is -no- reason that horse couldn't have been picked up within 24 hours. When we had to put Admiral to sleep, it was at 5:03 in the evening on a Saturday. I called the County and they had someone out the next morning (even though they are normally closed) and buried him for me. It only cost $50.00 too. They also were able to "move" him with their tractor. This was -before- i had a full boarding operation. I could ask so many questions, like "Why didn't the vet provide numbers for body pick up?" etc.. but it isnt what this thread is about.. LOL I've already went WAY off topic!
As far as the Salmonella thing goes, i'd be interested for learning more about it as well. I knew it was possible with horses but thankfully never experienced it.
... have you considered shopping around for another horse barn? LOL!