My rabbit adores cos lettuce and will practically rip it out of your hands. I then read on a couple of sites somewhere that you shouldn't give lettuce to rabbits because it was bad for them. Never seemed to do Sebastian any harm so I just reduced the amount I gave him and changed to darker green veg instead.
However last week I bought a copy of Rabbitlopedia and according to the author, there's a substance in lettuce which is the equivalent of opium :shock: I was horrified :shock: It certainly explained why Sebastian would relish every bite and then spend the rest of the night tranced out in his pen. I've taken him of it completely now and he seems to be a lot more alert (but that might just be me imagining it :? )
Having said all of this, I've read lot's of stuff in books/on sites only to have it completely contradicted by other stuff in other books and on other sites. Being a bunny owner can be very confusing!!!