Hello,
I have seen this regurgitation problem in my own Mexican bairdi breeding group. In this particular case, the problem turned out to be humidity related. This is what I have to say about the issue.
There are many possible factors causing regurtitation syndrome in Pantherophis bairdi, high levels of humidity is just one of them. First, it should be noted that bairdi's from different localities may react very different on humid environmental conditions. Mexican bairdi's, for example, are quite vulnerable. Bairdi's from eastern Texas, on the other hand, may (or may not) tolerate humid conditions as much as any other ratsnake. As a rule, it should be advised to use small surface watercontainers only. Use jars instead of bowls, and keep them away from the heat source. Also, it's important to use a (very) dry substrate. Faecal droppings should be detected easilly and removed as soon as possible. Keep in mind that bairdi has adapted to an environment quite hostile to bacterial pathogens, therefore selective forces driving immune response mechanisms are less significant for the survival strategy in Pantherophis bairdi. In other words, bairdi is much more vulnerable to bacterial contamination than most other american ratsnakes. So if you are keeping bairdi together in the same terrarium with, say, obsoleta or guttata, than you are actually asking for trouble. Free advise to all you crossbreeders out there: Don't! Another important factor is thermoregulation. Since bairdi is a montane species, thermoregulation is significantly more complicated than in most other ratsnakes. This can only be facilitated in a relatively large terrarium, plastic sweaterboxes may do fine for cornsnakes but these are not suitable at all for bairdi's. Keep the terrarium well ventilated at all times. The heat source should both be easilly accessible and easilly avoided as well. Another problem with montane snakes is prey size and feeding frequency. I advise to offer undersized food items only once a week. Too large or too often sooner or later will result in regurgitation, and the longer this problem is ignored, the more difficult it will be to resolve it. If you manage to live by these rules, you will have no problems keeping Pantherophis bairdi whatsoever.
If your ratsnakes already have acquired the regurgitation syndrome, just wait for a week or so and try feeding it a skinned food item. The vulnerable stomach tissue doesn't get irritated by stuff like hairs of feathers, and the digestive enzymes no longer have to penetrate thick layers of skin, making digestion a lot more easy. I have had good results feeding skinned one day old chicks. These food items can be offered a bit more frequently, also a nice trick to keep in mind if you want to breed your snakes. If all of this doesn't help, then you definately have a case for your veterinarian. A broad spectrum antibiotic, such as one of the more advanced ofloxazines, ultimately may be the answer to you problem.
I hope this helps. Greetings,
Herman Bronsgeest, The Netherlands.