Unfortunately I can't, as much as I would like to evidence my position on this matter. I've moved around quite a bit in the last two-three years, most of my books and papers were left in Massachusetts, which is a long drive from Colorado in order to make a point.
The best I can supply you with is a few logical steps that you may or may not agree with, in order to arrive at the conclusion that a diet of nothing but mice isn't the healthiest thing for an eastern hog.
Animals adapt to their environments in every manner, as a species, rather than as individuals, generations of natural selection causing a general adaptation towards use of avaliable resources, be this food, shelter, protection from predators or what the opposite gender will accept when it comes to passing genes along.
Eastern hognose have adapted to an environment where there are many other species that are, when looked at in certain generalities, very similar. There would be a great deal of competition for avaliable prey species between assorted species of snakes throughout the south eastern portions of the united states if individual species did not specialize.
Specialization is both positive and negative for a given species. In this instance, eastern hogs have evolved to become very very very very very good at prey collection, provided that the prey is amphibious and, even more specifically, toads. This means that they'll out-compete just about any other species when it comes to toad eating, but will not do well if their usual prey source is removed. Just another example of the ongoing battle between specialization and generalization on an evolutionary scale.
Some of the specific adaptations towards their intended diet are quite advanced. A general resistance to bufo toxins is present in a lot of snakes from the area... Eastern hogs have developed not only the ability, but the required physiological apparatus needed to not just resist, but collect and reuse those toxins. Their digestive system is amazingly efficient when it comes to breaking down and metabolizing toad tissue and many of the toxins they produce seem quite specific in their function. I'm not suggesting that you actually do this but... if you were to feed a hognose a mouse, then pull it out of it's mouth halfway down, it would be a bit moist. If you were to do the same with the toad, you'd find that the skin had already started dissolving, being digested by the enzymes present in the hognoses saliva.
Species which have adapted to a specific diet have done so to a degree which generally precludes them from reccognizing other food sources, except in an opportunistic manner. Their digestive systems evolve right along with those prey reccogniziton instincts to consume a certain type of food. A drastic example being say... Horned Lizards (I miss calling them horny toads) and ants. A more common example being savannah monitors fed nothing but dogfood and rodents, which get obese or green iguanas fed insects, which causes quite a few problems. Eastern hogs seem to fall someplace between the horny toads and the monitors... they're not entirely dependant on the chemical composition of their usual prey item, but they are adjusted to digest a certain nutritional balance. Toads and rodents are pretty different nutritionally, when it comes to caloric content, fat content, the amount of calcium present, the amount of indigestable tissue present... Long term, too much of a food that a species is not adapted to consume can be pretty damaging.
I know I've read studies which analyzed the digestive capabilities, geared mostly towards the accelerated digestion of amphibians, especially toads and I've seen at least a few veterinary reports which cite general, long term malnutrition as being the cause of death in specimens that were fed exclusively rodents. I also have no idea who wrote them, when they were written or, to be honest, if they're still sitting in the piles, shelves, boxes and furniture covering stacks I left in Boston.
Basically just a situation, like so many others, where the diet in the wild should be identified and something as similar as possible nutritionally should be given in captivity. If you agree with the logic presented above, good deal. If you don't, to be honest it's really no skin off my nose. I could probably find a few ebsites which support my statements but I'm distrustful of most websites and don't easily regard many of them as being a valid source of information, especially not when someone educated is requesting evidence. Too many people with too few qualifications writing most of 'em.
