I believe 'little gem' and 'romane' are both safe, altho lettuce itself is low in nutrients and its mostly water, the only time ive used it was to try and shift a bowl blockage.
mine love spring greens, its £1 for a large bags worth, normally in 2 large stems, or several small ones. I get these for the buns, so the hams get a leaf ripped into their daily veg
