I also offer my condolences. Losing one is always tough. I see this condition quite a bit in wild rabbit rescue. While the digestive systems of domestics and wild rabbits are idential in their workings, cottontails do wean a lot quicker and a lot more violently than domestics. The symptoms you describe are consistent with a major GI imbalance. As a baby rabbit starts to wean, the pH in the gut must convert from a somewhat neutral environment to a very acidic environment.....somewhere between a pH of 1-2. The mother's milk is critical in this conversion. That is why so many cottontails are lost in rehab. If the GI isn't acidic, the bacteria that is required for proper digestion can't survive. Since this bacteria not only digests food, it also controls the bad bacteria....harmful bacteria such as Clostridium and/or E Coli will grow rapidly. The rabbit will lose weight quickly, will get diarrhea (sometimes hard to see with a baby) with mucus and will quickly become lethargic as the toxins build. With such a young rabbit, there is little that can be done once this process starts. We are having a particularly difficult time with cottontails this year for some reason....and we are losing them in record numbers and in just the manner in which you described. We are going to do necropsies on "virgin" rabbits we lose (these are babies that have not encountered a cat or been fed improper formula). We suspect a nasty strain of harmful bacteria but time will tell.
I would like to comment on the carrots. While I do agree that carrots are not exactly health food....there is no reason that rabbits can't be weaned on greens. Remember that our domestics are from wild rabbits....and wild rabbits do not have pellets in the woods. Another misconception that lingers from the dark ages of rabbit husbandry. My cottontails (keep in mind their GI is identical to domestics with the exception of wean time) rarely get pellets. Only the ones here long term get high end pellets....and then it's only to provide proper supplements to allow for the lack of sunlight....and lack of sunlight (Vitamin D and Phosphorus) has a negative effect on the absorbing of calcium....and that is another myth....rabbits have bones and teeth and those need calcium. But rabbits can be properly weaned, if all things are in order, on greens only....pellets not required.
I suspect the loss of this rabbit was caused by a combination of stress and improper weaning from being too young that resulted in a condition known as Cecal Dysbiosis (among other names for the same condition). Most states, including this usually backward state of NC, require that rabbits be at least 8 weeks old before being offered for sale.Â
Randy