Richard Race, a research veterinarian at the National Institutes of Health's Rocky Mountain Laboratories , in Hamilton, Montana, explains that animal protein is more complete than most vegetable proteins, and that the best protein an animal can eat, metabolically speaking, is derived from the tissues of its own species. Donald Beermann, a professor of animal science at Cornell, observes that feeding animal protein to cows significantly accelerates their rate of growth. And, he says, animal activists are wrong when they claim that cows are strict vegetarians. Nature is not in the practice of wasting valuable nutrients. One may well ask, then, why most mammals approach cannibalism as, at best, a last resort.
Scientists can only speculate that such behavior bodes ill for a species' long-term survival.
Disease spreads more easily within than among species, and a species that eats its own has a higher risk of being killed off by disease. Cannibalism also amplifies levels of infectious organisms, concentrating and increasing their presence in the environment and spurring their chances of hurdling the species barrier and moving into another, related species. A microbe that normally infects sheep fed repeatedly to, for example, cows may mutate in order to accommodate to its new host, thereby becoming the agent of a cow disease. Gloria Dunnavan, the director of the Division of Compliance at the FDA's Center for Veterinary Medicine, says that although the agency is looking for 100 percent compliance on the regulation, it is not 100 percent optimistic. Not a lot of people in the rendering and feed industry are used to seeing an FDA presence.