Animals Make Us Human: Creating the Best Life for Animals

by Dr. Temple Grandin and Catherine Johnson

Houghton-Mifflin Harcourt, New York, NY, 2009
ISBN 978-0-15101489-7

(In United Kingdom, book title is "Making Animals Happy" and ISBN is: 978-0-7475-9714-8)

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An Excerpt from Chapter 7: Chickens and other Poultry

Animal welfare problems in chickens and other poultry caused by single trait genetic selection for meat and egg production

Chickens have several serious welfare problems that come from bad genetics and can be fixed only with good genetics The biggest problem in many intensively raised animals is pushing the animalís biology for more and more production. Breeders choose the most productive animals ó the fastest growing, the heaviest, the best egg layers, and so on ó and selectively breed just those animals. Bad things always happen when an animal is overselected for any single trait. Nature will give you a nasty surprise.

Bone breakage is a very serious problem in both caged and cage-free hens because laying hens have been overselected for egg production. Commercially bred hens put all their calcium and minerals into forming eggshells, and their own bones become depleted. Their bones are so weak that in cage-free systems a hen can break her leg just jumping off her perch. The only way to solve this problem is for the industry to accept the fact that birds with strong bones will produce slightly fewer eggs.

Laying hens have other problems, too, especially feather pecking and cannibalism. Feather pecking is what it sounds like: one hen pecks at another henís feathers or pulls a feather out all the way. Severe feather pecking can lead to cannibalism, with the victim hen being wounded and then killed by the hen doing the pecking. Even though a feather-pecking hen can kill her victim, feather pecking probably isnít driven by the RAGE system. We know this because of studies mixing unfamiliar hens together. Aggression goes up, but feather pecking and cannibalism donít. They arenít the same thing.

Instead, feather pecking is probably displaced or redirected SEEKING behavior. Itís a kind of foraging or exploration of another bird instead of the ground. We know this because of research showing that chickens housed on litter do a lot less of it. They peck at the litter on the ground, not at each otherís feathers. The more active the bird and the more foraging behavior it does naturally, the more likely it is to develop severe feather pecking. Both feather pecking and cannibalism are affected by genetics.

Some modern broiler chickens have genetic problems related to growth. I was shocked to learn at a chicken-breeding seminar that the broiler chicken has been so overselected for rapid growth that its bone physiology is totally abnormal. In normal bone development, the body first ďerectsĒ a scaffolding or frame of cartilage and then fills in the frame with minerals that harden into bone. After the bone has hardened, the cartilage dies off through programmed cell death. In broiler chickens, something goes wrong with the cartilage, so the bones donít have support while theyíre hardening and end up misshapen. I liken it to building a new basement wall and taking down the plywood concrete forms before the concrete has fully hardened. In some of the worst cases, a chickenís feet are rotated almost 90 degrees and the legs are twisted. These chickens are genetically lame. Several studies have shown that lame broilers will choose feed laced with painkiller over their regular feed, and a study of lame turkeys showed that they started moving around a lot more once they were on painkillers. The industry has created chickens that have chronic pain in order to get birds that grow at the far outer limits of what is biologically possible. When an animalís biological system is pushed to the point where the physiology is totally pathological, I get disgusted.

The other problem is that modern broiler chickens have been bred to have stupendous appetites so theyíll grow super-fast and reach market weight as soon as possible. The trouble is that the breeder chickens, the parents of the broilers, have the same stupendous appetites as their chicks. If you let a broiler breeder chicken eat everything she wants, she will become obese, her fertility will decline, and her life will be shortened. These chickens have to be kept on a strict diet just to maintain normal weight. They act miserable, and many of them develop stereotypies. These birds have low welfare no matter what you do. If you let them eat all they want, they have bad welfare and if you donít let them eat all they want, they also have bad welfare. Itís terrible. The industry is going to have to breed parent stock with smaller appetites. Thereís no other way to fix the problem.

Then there are other genetic problems that no one understands. One of the worst cases was the rapist roosters. I wrote about them in Animals in Translation. Fortunately, the broiler industry has made some genetic changes to correct these problems, although thereís still a way to go. The rapist roosters violently attack hens and injure and even kill them. Before the 1990s there werenít any rapist roosters. They just suddenly appeared out of the blue. First it was just one strain of roosters that had become aggressive but within a couple of years almost all strains had developed the same behavior. Nobody knows why.

The rapist roosters have two problems: They are hyperaggressive and they have stopped doing the courtship dance the hen needs to see before she will mate. Theyíve lost the little piece of genetic code that makes them do the dance. When the hens donít see the courtship dance, they donít become sexually, which may make the roostersí aggression worse. An unreceptive hen would be a form of frustration because it is a restraint on the roosterís action. So the RAGE system would be activated to some degree.

When I wrote Animals in Translation it looked like the rapist roosters were a side effect of the industryís selective breeding program to create chickens with bigger breasts for more white meat. But now researchers arenít sure what caused it, or whether the hyper-aggression and the bad courtship behavior are the same problem or two different problems that happened at the same time. Industry breeding programs are trade secrets. Itís obvious the industry is selectively breeding for larger breast size because breast size is getting larger. But we donít know what other selective breeding programs the industry might be using.

Ian Duncan has an interesting theory about what might have happened. Dr. Duncan points out that big-breasted male birds have trouble mating because their huge chests get in the way. Male turkeys have such big breasts now that they canít mate at all and the hens have to be artificially inseminated.

Dr. Duncan says that if the same thing is happening to male chickens, the broiler breeder industry may have misdiagnosed the problem. When broiler breeders see chickens with decreased fertility, they attribute the problem to low sex drive. Itís possible that the breeders who created rapist roosters were actually trying to increase roostersí sex drive. If the breeders selected for higher libido they could have mistaken a little bit of aggressive behavior toward the hen for higher sex drive and ended up breeding hyper-aggressive roosters that for some reason had also lost their courtship dance. Weíll probably never know.

Today the aggressive rooster problem has been greatly reduced although it hasnít been eradicated.

Better Breeding Strategies using Group Genetic Selection

Most of the time breeders deal with genetic problems by culling chickens that have the problems and mating the ones that donít. Another interesting approach is group selection. The researcher Bill Muir at Purdue University has shown that you can reduce feather pecking genetically by using a technique called group selection. With group selection, instead of picking certain individuals, you pick certain family groups to breed. Dr. Muir has done this by raising several ďsire familyĒ groups ó groups of chickens related to each other through their father ó and then selectively breeding the group that has the highest egg productivity and the lowest amount of feather pecking and cannibalism.

Group selection has a couple of advantages over individual selection. First, the fact that youíre working with groups instead of individuals means you know something about the birdsí behavior in a group. When breeders select high-productivity, individually housed laying chickens to breed, they donít know whether they are feather peckers or not because theyíve never lived with other birds. Individually housed laying hens canít express the behavior.

Second, when you have a group of genetically related chickens living together you also see how living in a group affects their behavior and productivity. When you choose which group to breed, youíre not just choosing one genetic strain of chickens over another, or two desirable behavioral traits (good egg laying and low feather pecking) over undesirable traits. Youíre choosing one way of relating to the environment over another.

This is important because most behavior is affected by whatís going on in the environment. A hard-wired behavior like the courtship dance is always the same no matter whatís going on in the environment. Itís like a computer subroutine; once you turn it on it just runs. But everything else is affected by the environment. When breeders use group selection instead of individual selection, theyíre factoring in the way the selected group relates to its social and physical environment.

Today, only a handful of companies provide all of the commercial layers and broilers around the world, which has greatly narrowed the gene pool. This has created a risky situation because genetically similar animals are vulnerable to the same diseases. Sure enough, when the Australians phased out their homegrown broilers and imported American birds, they ended up with more disease problems.

This is why itís important to preserve the old breeds of animals and poultry. Keeping the classic breeds alive is the only way to preserve genetic diversity and to save animals that have valuable genetic traits breeders may want to breed back into commercial lines in the future. The meat from some of the old breeds is more tender and better quality than meat from animals bred for rapid growth, and the chickens are hardier, too. They perform better in pasture-based or organic farms. They are beautiful, unique animals that shouldnít be destroyed by commercial breeding. Fortunately, many of the older breeds of poultry and livestock are being raised by local farmers and sold in farmerís markets or to gourmet restaurants. If a serious disease ever kills commercial broilers or layers, the entire world will be thanking the small producers and hobbyists who have kept the old breeds of chickens from becoming extinct.


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