I know this is an old thread that I'm reviving from the dead, but I had bookmarked it sometime ago until I could ask my vet his opinion about it. Well I took my new Kingsnake for an initial checkup and asked him. He said there is no current proof to support the theory that rats are in any way better than mice - whether looking at fat, protein or calcium there just isn't much difference. He even referred me to the Bronx Zoo study mentioned in IMO's post.

Bottom line, feed prey that is proper in size for your snake.
Exactly what my vet said! He said people get too caught up in the rats are better thinking. There's just no proof and the most important thing is proper prey size and husbandry.


He also told me that it is much better to feed say 2 smaller prey in a feeding versus 1 larger prey item.

Again, just thought I'd add this in as this was one of those unsupported theories I kept hearing people throw around when I first got my BP. It just stressed me out - especially since people just kept saying it but couldn't back it up. Now at least there's some research to look at.