Do you insist on free-range eggs? Do you support medical research on animals? Do you think all research that uses animals should be banned? Our concern for animal welfare takes many forms, from veganism to militant extremism. Less familiar are the scientists who, accepting that practices like intensive farming will occur, devote their research to developing more humane ways of managing the animals we exploit. Dr. Joy Mench of the Department of Animal and Avian Sciences at UC Davis has spent almost 10 years studying domestic chickens with an aim to improving the quality of their captive lives.
The subjects of much of her research are a type of chicken known as "broiler breeders". For most of us, the factory-farmed laying hen is the poster child for poultry welfare reform, kept as they are in a concentration camp of tiny cages. In contrast, broiler breeders - the breeding stock for broiling chickens - are not as densely housed and so receive less press. Nevertheless, their conditions also raise serious welfare concerns.
Here's the difficulty faced by the birds. Broilers have been genetically selected through breeding to have super-large appetites and consequently super-fast weight gain. The problem is that the birds don't just become plump. Their voracious appetites lead to such obesity that if allowed unlimited food, they have trouble standing, let alone breeding. Broiler males used as breeding stock, therefore, must be fed on restricted diets and maintained at about 50% the weight of birds destined for the oven. This regime keeps them fit and trim, but from the viewpoint of the chickens, who have been bred to feed, they're starving. The result of this "feeding frustration" is heightened aggression in males as measured by pecks to other birds. Chronic hunger also leads to elevated levels of stress hormones in the blood, an indication in animals that they are distressed or "unhappy".
These days when Americans are chronically distressed or unhappy many of them take Prozac. This drug is linked to the production of serotonin, a chemical in the brain with wide-ranging affects on behavior in humans and other animals. In her search for ways to reduce aggression and stress in food-restricted male chickens, Dr. Mench and her colleagues studied the effects of a Prozac-like substance called tryptophan, an essential amino acid that animals get from their diet. Tryptophan is necessary for the production of serotonin.
The researchers found that broiler males fed on diets with an added dose of tryptophan peck their fellow chickens significantly less than do birds who's food was not supplemented. Interestingly, the drug's seemingly calming effects interact with dominance rank - literally, the "pecking order". Tryptophan made the biggest difference in the most dominant birds.
Tryptophan appears to have no harmful side effects on health or reproduction in broiler breeders, and reduces various types of aggression in other species as well. For example, researchers find that it significantly decreases the stereotyped self-mutilating behavior that sometimes develops in caged monkeys.
Are drugs the answer then? Should we just put all our livestock and laboratory animals on Prozac? Dr. Mench feels that while "mood altering" drugs are an important tool in helping animals to cope or preventing stress or injury we should view them as a band-aid until we design management practices that improve welfare. For this, we need to create environments that address animals' natural needs. For example, chickens have a strong urge to forage, scratching through floor litter in search of tidbits, so much so that in choice tests, they choose to "work" for their food rather than eat it straight from a container. When Dr. Mench put baling hay on the chickens' floor for them to search through, their levels of stress hormones declined. Being able to forage, even if they weren't eating, seemed to lower their feeding frustration.
In a kinder, gentler world, the eating public would not insist on such succulent meat at such cheap prices, demands that fuel intensive commercial farming practices. Perhaps the time will come when all inhumane treatment of animals, whether it be in chicken factories or laboratories, will be banned. But that day is a long way off. In the meantime, scientists like Dr. Mench are seeking to improve the conditions of animals today.
Dept. of Anthropology, University of California, Davis, CA 95616.
e-mail: kjstewart@ucdavis.edu