Undernourished Bull Snake.

[spyderman]

3 Weeks ago, I got a Bull snake from a friend of my son's who couldn't handle it because it always nipped him & was only feeding it 1 small mouse a week. He was VERY undernourished. Since I have had him, I have been feeding him 1 small Rat for the first few weeks. Last week I gave him 2 small Rats which he took quickly, one after the other because I was told that a snake will only take what it needs to & leave what he can't eat. Please help me confirm this as I will be feeding him again this Sunday & I don't to risk overfeeding him. Should I stick to one or two Rats?

Ekans (The snake) is about two years old & 4-5ft long. & I can see his backbone.

He otherwise has a clean bill of health.