moderately underweight senior rabbit

Question
I have an 8.5 year old neutered male who is a bit underweight, probably due to a small tumor growing on his lower jaw (see below).  We would like to see him put on about a pound.  I'm trying to research what the best ways to give him a little extra "boost" in his nutrition would be.

There are two important notes with him: he has a very mobile, unattached tumor (about the size of half a small grape) on his jaw which is being removed later this week, but it seems to be interfering with his chewing and he prefers softer food.  He is still eating oat hay (more than he used to, actually), as well as his greens and Oxbow pellets, although he takes them in more slowly than he used to and doesn't always finish his pellets.  The other issue is that he had a cystotomy about five years ago and had a fairly large bladder stone removed, so I am wary of increasing his calcium by giving him any alfalfa products.  He has not had urinary issues since then, but I don't want to add to his problems!

I'm wondering if a small portion of a human supplement like Ensure would do him any good.  Do you have any suggestions?

Answer
Dear Cianne,

We've occasionally used Ensure or similar products to boost caloric intake.  As long as your bunny's GI tract (and flora) don't react to the added sugar with mushy poop problems, that's a good way to increase his calories.  You might also try fluffing his pellets so they're easier for him to chew.  Just add enough water to cover them in his bowl, then microwave for about 10 seconds (just long enough to get it *slightly* warm), and then allow to sit for about five minutes.  Fluff with a fork, and it becomes very nice, easy-to-chew pellet fluff.

Other higher calorie foods can be offered in moderation, such as a banana slice in the morning and evening, and maybe a tablespoon of whole oats.  Always be vigilant for any sign of cecal dysbiosis (you'll see mushy poop), and cut back on starchy food if you do see that.

Hope all goes well with his surgery!

Dana