The green leaf lettuce will be alright but for short term. How long will you be out of the kale &
arugula? It has a higher water content so give in moderation so it wont give him diarrhea or
anything.
Green + red leaf as well as romaine are O.k, they certainly do have nutritional value but are not as good as the greens like turnip, mustard, collard, arugula, dandelion, kale. You can use a little bit of the lettuce but go back to the others once they are available since they are more nutritious.