A COK Report:
Animal Suffering in the Broiler Industry

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Selective Breeding

The vast majority of chicken meat we find in grocery stores and restaurants comes from "broiler" chickens intensively confined on "factory farms." Each year in the United States, more than 8 billion chickens are raised on these farms.(1) These chickens suffer both acute and chronic pain due to selective breeding, confinement, transportation, and slaughter.

In the 1950s, it took 84 days to raise a five-pound chicken. Due to selective breeding and growth-promoting drugs, it now takes an average of only 45 days.(2) To put the growth rate of today's chickens into perspective, the University of Arkansas Division of Agriculture reports, "If you grew as fast as a chicken, you'd weigh 349 pounds at age 2."(3) While this rapid growth increases profitability, it also aggravates health problems among chickens.

The leading health problem caused by fast growth is the high rate of leg disorders causing crippling lameness.(4) Broilers' bone growth is outpaced by the growth of their muscles and fat. In one study of lame chickens, 20 percent had bacterial infection of the bone, 13 percent had visible leg deformities, 11 percent had spondololisthesis (slipped vertebra typically caused by degenerative spinal disk disease), and 11 percent had tibial dyschondroplasia (a condition characterized by an abnormal mass of cartilage preventing normal bone development, which may lead to bone fragility, distortions, and infections).(5) Another study estimated 30 to 49 percent of broilers suffer from tibial dyschondroplasia.(6) One study found that 90 percent of broilers had a detectable abnormality in their gait.(7) These deformities are known to be painful.(8) One survey found that 26 percent of broiler chickens were suffering chronic pain in the last weeks of their lives as a result of bone disease.(9) Another researcher concluded, "Broilers are the only livestock that are in chronic pain for the last 20% of their lives. They don't move around, not because they are overstocked, but because it hurts their joints so much."(10)

Lameness causes many chickens to be unable to support their own weight. At six weeks, broiler chickens have such difficulty supporting their abnormally heavy bodies that they spend 76 to 86 percent of their time lying down.(11) This, in turn, leads to breast blisters, burns, and foot pad dermatitis.(12) Contact dermatitis due to lameness has been shown to affect up to 20 percent of broiler chickens.(13) Because sheds are not cleared of litter and excrement until chickens are taken to slaughter, the birds have no choice but to stand in their own waste. As a result, bacteria often infect skin sores, leading to disease.(14)

Severe leg deformities are fatal if birds can no longer stand to reach food or water.(15) One to 2 percent of all birds die due to leg problems.(16) One group of researchers concluded, "We consider that birds might have been bred to grow so fast that they are on the verge of structural collapse."(17)

In addition to lameness, intensive breeding for genetic selection has caused broiler chickens to suffer from respiratory disease, coccidiosis (a parasitic infection resulting in sometime fatal blood loss), inclusion body hepatitis, leg weakness, big liver spleen disease, acute death syndrome, and ascites.(18) Broilers selected for faster growth suffer from weakened immune systems, making them more susceptible to a variety of diseases.(19)

In acute death syndrome (ADS), chickens suddenly lose their balance, violently flap their wings, go into spasms, and die. Between 1 and 4 percent of broilers may die of ADS.(20) The syndrome is a form of acute heart failure caused by fatal arrythmias, which are common in broiler chickens and have been linked to their rapid growth rate.(21)

Another typical condition among broilers is ascites, in which the heart and lungs do not have sufficient capacity to support an overgrown body.(22) Ascites is responsible for 5 to 12 percent of mortality in broilers.(23) An industry journal reports that "broilers now grow so rapidly that the heart and lungs are not developed well enough to support the remainder of the body, resulting in congestive heart failure and tremendous death losses."(24) Heart failure is taken less as an indicator of poor breeding and more as a sign of optimal production. As one chicken farmer wrote, "Aside from the stupendous rate of growth...the sign of a good meat flock is the number of birds dying from heart attacks."(25)

Despite the health problems described above, producers continue to breed birds for fast growth. One study found that selection against leg disorders came only ninth out of 12 factors taken into account by the breeders of broilers, with growth rate and feed efficiency being first and second.(26)

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