why?
Basic hygiene really. Frozen meat out in hot weather will be teeming with bacteria and flies in no time. I don't see anything wrong with giving very small bits of frozen meat you'd know they'd eat pretty sharpish, just not large parts/whole rabbit that would be lingering about in the heat growing god knows what all over it.
i take it you dont feed whole carcuss to your monkeys then, if you have enough of them how long do you think it lasts once defrosted