Ruminants: Talk about your iron stomachs!
Ruminants, such as cows, sheep and deer, occupy an important niche in the world of nutrition. First of all they free up the vast amount of energy stored in the form of cellulose, a complex sugar which cannot be digested by simple stomached animals such as humans or dogs. Cellulose can be digested, however, by the population of microorganims that lives in the rumen and reticulum, and the energy released by this digestion passes along the food chain to the ruminant and to the lucky carnivore that eats the ruminant.
These rumen microbes serve another important function: they defend the ruminant and those higher up on the food chain from the score of toxic substances lurking used as a defense mechanism by plants. These toxicants are degraded or inactivated by the rumen bugs. This includes trypsin inhibitors, lectins, gossypol, glucosinolates, and certain pyrrolizidine alkaloids.