If they are not interrupted, devils can eat up to 40% of their body weight in 30 minutes. But as they need to consume about 15% of their body weight per day in the wild, even a huge feast like that would only keep them going for 2 or 3 days.
In some areas, particularly farm land, much already dead stock is eaten. Generally dead cows can only have small bits eaten - the udder, the mouth, the anus - because the skin is too thick for devils. Whole sheep can be eaten except for the large bones. Any small stock like sheep or lambs that are injured or incapacitated may be killed and eaten. New born lambs are sometimes at risk. If sheep have twins or triplets, weak members of the litters may be especially vulnerable. Poultry that roosts on the ground is also vulnerable. Most healthy stock is perfectly safe.