Believe it or not, pure canned pumpkin is a good appetite stimulant for bunnies. When my long-eared friends had gastro-intestinal stasis, I used a syringe with a little pure pumpkin in it to force-feed them. Rabbits need to keep food flowing through their digestive system or they could die. Pumpkin is one food that they consider as a treat. Though this method of jump-starting a rabbit's bowel isn't fool proof, I've used it successfully many times.
In addition to curing gastro-intestinal stasis, I've fed canned pumpkin to rabbits with tooth problems. Mark, my recently deceased bunny, had a jaw infection and bad molars. To keep him hydrated and to keep fibre in his gut, I fed him the pure pumpkin each day. He loved it so much that it was the highlight of his morning. You can see how enthusiastic he was on my Bruce Atchison YouTube channel.
I should mention that only 100% pumpkin should be used for these occasions. The seasonings, and especially the sugar, added to pumpkin pie filling aren't at all good for rabbits and their delicate digestion. The reason sugar is deadly to bunnies is that it causes bad bacteria to grow explosively in their intestine and release toxins. Many rabbits have died because their caretakers gave them too many sweets such as dried apple bits or carrot. Only a tiny piece of these treats should be given at infrequent intervals.
Speaking of giving pumpkin to animals, my next door neighbour gives her dogs some as a treat. They wolf it down, according to her. I don't know what benefit they receive from eating pure canned pumpkin but I know the fibre and nutrients help bunnies. They also love the taste.
There are two excellent books about bunnies that I recommend. One is The House Rabbit Handbook, available from The House Rabbit Society and When a Man Loves a Rabbit: Learning and Living with Bunnies. The first book gives you all the "how to" tips while the second one lets you know what you can expect from house rabbits. See the left side of this page for more information on that book.
I also have a new book out called How I Was Razed: A Journey from Cultism to Christianity. Find out more about this remarkable story of how God led me out of darkness and into his light at Amazon, Barnes & Noble, and Virtual Bookworm Publishers.