I fully agree about the Oxbow products. They make a fantastic line of products,very high quality. I normally purchase their all Timothy Pellets for which 3 Vets have simply told me"Kudos" on the product. I normally buy the Oxbow products on line only because my work schedule allows little time for shopping. I also agree with the other post though that if you can purchase their products in store to save on the shipping charges.
I cannot stree enough though that you work hard to find a remedy for the poopy bottom. The secondary problems to such can be catastrophic to say the least. My little Cotton guy was seven and most of his life had a poopy bottom. We swicthed his diet many times but never could quite work through the issue. This included multiple Vet trips on the matter. This though resulted in our washing his bottom often. Though he was a house bunny as he aged he tended to let his guard down and at some point near the end of this past summer a fly struck him. This took place in a skin fold where even the Vet said it was not noticeable. We only realized what had happened when Cotton started exhibiting sign of pain. I realized what had happened late one friday night at about 1 a.m. At this time I rushed the little guy 45miles through the dark of night to a 24 hour animal ER. To make a long story short he passed away 3 days after that trip and one other trip tot he local Vet. Both Vets missed the fact that potent pain meds are needed in Fly Strike and should always be the first course of treatment in such, "Always". The again we missed this to. It most likely happened from a poopy bottom. Though we kept it clean this resulted in damp fur around his bottom many times. Damp fur will also invite fly strike.
Work hard on the diet and don't give up. The quicker you find a remedy the safer and happier the bunny will be.
take care