When any organism expires, it starts to decompose, and bacteria immediately starts breaking it down. My friend bow shot one in ohio last year shortly before dark, and he went back the next morning for it. he dressed it and it had a green slime inside it. he dismissed it and claimed/tagged the deer anyway. When he got home his butcher friend told him it was bad.

The longer you let that animal lie there with its innards intact, the faster it will start to break down, even on a fairly cool day, you will be surprised how fast that process can damage that meat.

We owe it to the animal to utilize it, and taking care of it should begin immediately. I would imagine most slaughter houses don't kill a bunch of cows, and come back 5-6-8 hours later to process them.