I read all the posts. I now have experience feeding three rabbits on oat hay. They just love it. They like to chew it and they like to eat the oar kernels.
When talking about feeding rabbits, keep in mind they have two stomachs. One stomach is like ours..its at the end of the esophagus and it joins onto the small intestine. The rabbit's second stomach is at the juncture of the small intestine and the large intestine...it's the Cecum. In humans, it's a vestigle organ know to us as the appendix. The Cecum is a very important stomach for rabbits. It's where the rabbit's vegetarian cellulose food gets transformed to glucose. The bacteria in the Cecum feed themselves with this glucose and the excess glucose these bacteria make goes to feed the bunny.
My experience feeding house pet rabbits is that they know instinctively how to eat. I've seen situations where I've feed my rabbit banana slices/apple slices to where she didn't want to eat any more, but then she would aggressively start eating greens (carrot tops, etc). The fruit was food for her first stomach and for hunger that could certainly satiate her. But this food was digested in her first stomach. She had an instinctive urge to eat greens to feed the symbiotic bacteria in her second stomach. These symbiotic bacteria, that transform cellulose to glucose are essential for a rabbits life. The rabbit had an instinctive urge to eat food that will feed these bacteria.
Our past rabbit Bunny, and our now two Flemmish girls, have all the food they want to eat. Fresh green veggies are in their food bowls, rabbit pellets, oat hay in their litter boxes for chomping, and pretty much fruit slices as they want...our only reluctance with feeding them fruit is that we don't want them to get too fat. No problem with diarrehia.
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Haven't fed to the Flemmish yet, but Bunny liked bing cherries, unsalted almond slices, guava's, unsalted peanuts.