SOME lads i have known feed a full meal at tea time 5pm ish, with no ill efects, the thing to remember is if your lamping after midnight , the food that went in will be out of the stomach anyway, and in the small intestine,, and be well digested of course this depends on what they have eat. big chunks of bone would take longer to digest, but you wouldnt feed that. but regular minced beef/lamb/chicken , and meal would be broke down.