I don't think we need to be too concerned about the prey our snakes eat other than trying to feed too large of a rat/mouse. In the wild, they eat what comes along. Today, they'll eat a 20 gram rat, next week, they'll eat a 60 gram rat. As long as the snake is eating,

If the pet shop doesn't have the size you usually feed, then drop down a size. Feed one or 2, it doesn't matter.

Jim Smith