Grain-eating birds

The dietary requirement for nicotinamide is also related to the requirement for tryptophan. Dietary tryptophan can be converted with varying efficiencies into nicotinamide, thus dietary tryptophan spares the requirement for nicotinamide. In the domestic fowl and grain-eating birds, there is rarely an excess of tryptophan. Pyridoxal phosphate (vitamin B ) is required for the interconversion of tryptophan to nicotinamide, and so the requirements for nicotinamide are moderated by the amounts of pyridoxal and of tryptophan residues present in the diet. The ability to convert tryptophan to nicotinamide also appears to depend on the level of picolinic acid carboxylase in the liver. This enzyme converts one of the intermediates, 2-amino-3-acroleylfumaric acid into a branch path and so competes with the main pathway. The levels of this enzyme are comparatively low in the domestic fowl but are much higher in the duck, which fits with the duck having a nicotinamide requirement about double that of the domestic fowl (Scott et al., 1982). 

Nature is full of drugs. Even animals use and abuse drugs. For example, birds eat certain kinds of berries that ferment on the tree, literally getting drunk on them until they can barely stagger, let alone fly. Elephants have been known to seek out piles of grain fermenting in the fields and even learn to break into enclosures where such grain is stored. Made rowdy by the effects of the alcohol, the elephants can be a serious or even deadly nuisance. 

Apparently a frog itself does not produce the alkaloid toxin, for a frog kept in a controlled environment does not have the toxic alkaloid. It has been demonstrated that frogs get the toxins from the preys they eat, such as ants, termites, and flies, and they also seem to be able to modify the chemicals to make them more deadly. One of such preys has been identified as Choresine pulchra, a small beetle of about a rice grain size. As might be gathered from this description, similar alkaloids including batrachotoxin, have been found in some birds as well. 

---