Introduction
Of the 9.5 billion land animals raised annually in the U.S. meat production industry,[1],[2] farmed birds[*] make up the overwhelming majority—more than 9 billion broiler chickens and 270 million turkeys slaughtered each year.[3] On industrialized factory farms, chickens and turkeys are confined by the tens of thousands in large, dimly lit,[4] warehouse-like sheds,[5],[6] completely barren except for litter material on the floor and long rows of automated feeders and drinkers.
Chickens and turkeys are selectively bred for rapid growth and increased muscle (meat), reaching slaughter weight in increasingly shorter periods of time. In 1920, a chicken reached 1 kg (2.2 lb) in 16 weeks, but broiler chicken strains may now reach 2.27 kg (5 lb) in only 7 weeks.[7] Turkeys now reach 15.87 kg (35 lb) in 132 days, rather than the 220 days it took 40 years ago.[8] As a result of this rapid growth, many chickens and turkeys struggle to withstand the pressures their weakened bodies endure. Many suffer from gait abnormalities[9] and painful skeletal disorders,[10],[11],[12] serious welfare issues that can be exacerbated by catching and handling procedures,[13] a major cause of stress and injury for these animals.
Conventional Manual Catching
When birds raised for meat reach market weight, they must be caught and crated for transport from production facilities to slaughter plants. In the United States, most farmed birds are caught by hand by "catchers." Turkeys are caught by one or both legs, or by one leg and the opposite wing,[14] and chickens are typically carried inverted by a single leg, three or four birds per hand,[15],[16] before they are put into transport crates. During an average shift, a single catcher will lift 5-10 tons of birds at a rate of 1,000-1,500 animals per hour.[17],[18],[19] Catching the birds is a physically demanding task,[20] and, as researchers report, "[f]or a member of a catching team, it could be difficult to maintain concentration and exercise care throughout a longer catching time."[21] Rough handling, which causes birds to experience fear,[22] can increase as crews become weary from physical exertion. Researchers have concluded that "as fatigue sets in, one's primary motivation becomes just getting the job over with. Catching and crating the birds as quickly as possible with the minimum effort possible becomes the major focus. Careful handling becomes secondary."[23]
Birds raised for meat are typically unaccustomed to being touched by humans. When handled, farmed birds experience fear[24],[25] and stress, as indicated by physiological measures of elevated plasma corticosterone levels[26],[27] and heterophil/lymphocyte ratios.[28] The method of handling can also affect stress. Researchers have reported that carrying multiple birds at once and carrying birds in an inverted position both elevate plasma corticosterone levels compared with the practice of carrying single birds and holding them upright by their bodies.[29]
As such, manual catching, as well as handling and loading for transportation, have been identified by researchers as "major sources of stress and trauma to the birds."[30] Injuries associated with conventional manual catching have been well-documented in scientific studies and the lay press. For example:
- A study published in the Journal of Agricultural Engineering Research reported that up to 20% of birds experienced injuries during catching that led to downgrading of the carcass.[31]
- The Wall Street Journal reported that "[u]p to 25% of broilers on some farms are hurt in the [catching] process."[32]
- Reports from slaughter plants show that birds exhibit bruising of the breast, thighs, or wings at the rate of 5-25%.[33],[34]
- According to industry trade journal Poultry, 90% of bruises recorded at slaughter plants are caused by catching and crating.[35]
- In a study appearing in Poultry Science, nearly 3 out of 10 (29.5%) of dead-on-arrival (DOA) broiler chickens at slaughter plants exhibited trauma that the authors attributed to catching and crating.[36]
- A scientific review of transport systems reported that 35% of DOA broiler chicken mortality was due to trauma associated with catching and transport injuries.[37]
- In a study published in The Veterinary Record, causes of DOA mortality included hemorrhages associated with dislocated hips, thought to occur during catching and carrying by one leg, and crushed skulls attributed to heads caught as the door to transport modules were closed.[38]
In a review of welfare problems caused during catching and transport of farmed birds, Toby Knowles, professor of Farm and Food Science at the University of Bristol, and Donald Broom, professor of Animal Welfare at the University of Cambridge, concluded, "[T]he most traumatic stages of the process and the stages most likely to give rise to physical damage, are the times when the birds are manually handled."[39]
Alternatives in Bird Handling
Alternatives to conventional manual catching practices, including mechanized catchers,[40] gentle handling techniques,[41] and herding into transport modules,[42] exist and are able to cause less stress and/or injury to birds.
Welfare Advantages of Mechanical Harvesting
Commercially available automated catching machines are increasingly being used by the poultry industry, particularly where labor costs are high or where the work force is scarce.[43] These mechanical harvesters gather birds with soft rubber-fingered rotors and pull them onto a conveyer belt to transport crates.[44],[45] Automated catching may cause birds less stress than conventional manual catching,[46] as the machines reduce the amount of time the birds are in physical contact with humans, handle the birds upright, and may move the birds more gently.
In a study published in 1986, Ian Duncan, Emeritus Chair in Animal Welfare at the University of Guelph, and his colleagues reported that elevated heart rates and tonic immobility (TI)—indicators of stress and fear, respectively—were shorter in duration among birds caught by a prototype harvester and concluded:
The differences in duration of TI...suggested that the machine-caught birds were no more fearful than those treated as gently as possible by hand. Tonic immobility in the manually-caught birds lasted about twice as long, suggesting that they were much more frightened. These results indicate that short-term stress associated with the catching of broiler chickens can be considerably reduced by using a carefully-designed machine instead of catching by hand.[47]
The type of mechanical harvester may be important. In contrast to Duncan et al.'s early findings, a 2005 study found that automated catching by a "Chicken Cat" machine was not associated with any significant improvement in physiological measures of stress.[48] However, a 2006 study of the CIEMME Super Apollo L harvester reported lower stress levels and shorter TI durations (i.e., less fear) in chickens tested at the end of the catching period, when the production shed was nearly empty.[49] These results suggest that the Apollo harvester may be more effective in reducing stress at certain points in the catching process.
In addition to reductions in stress and fear, mechanically caught birds may also suffer fewer injuries. Although one study failed to find a difference,[50] several studies that examined a variety of different automated harvester models, have shown significantly less bruising[51],[52] and wing hemorrhaging[53] when birds are caught by machine. Field experience corroborates these studies' findings: Perdue Farms reported a 14% decrease in bruising among birds caught by machine.[54] A 2003 study found that, compared to conventionally manually caught birds, those caught with a "Chicken Cat" machine experienced significantly lower incidences of leg and wing fractures and dislocations: Leg, wing, and rump injuries were 50%, 22%, and 27% lower, respectively, and the percentage of birds with one or more injuries was 30% lower than those caught manually.[55]
Two potential disadvantages to mechanical versus manual catching exist, both related to personnel. Workers operating automated harvesters may be less likely to remove dead birds or cull those who are sick and likely to die during transport. Several studies have reported higher rates of dead-on-arrival (DOA) birds with mechanical harvesting,[56],[57],[58],[59] attributed to the inclusion of birds who were already dead or sick in mechanically loaded crates. Additionally, the use of mechanical harvesters requires both training and experience, and the animals' welfare could be compromised during the period in which personnel learn to effectively operate the machinery.[60]
Welfare Advantages of Gentle Manual Catching
Birds can also be caught gently by hand. One study measured rates of injury and DOA using an automated Tekniikka "sweeping catcher" and a gentle manual catching technique common in Sweden, where birds are carried upright in pairs.[61] The gentle manual method caused significantly fewer bruises and fractures than mechanical harvesting,[62] and these injury rates were very low compared to the figures attributed to manual catching crews in the United States.
At this time, results are not yet definitive. Much could depend on the machine used and the level of training received by operators. However, findings do suggest that, at least under some operating conditions, gently handling birds upright in pairs causes fewer injuries than other catching methods. (Corticosterone levels were not measured, and no conclusions were made about stress.[63])
It is unclear whether the Swedish method would be adopted in the United States and elsewhere, as it requires training and possibly economic incentives for catching crews to slow their catch rates, which would likely increase labor costs for industry. As noted by researchers, while it is possible to manually catch and crate chickens with almost no harm to the birds, the process is arduous and it is difficult to maintain the concentration and attitude necessary to handle the birds carefully throughout a 5-8 hour work period.[64],[65]
Welfare Advantages of Herding into Transport Modules
Rather than catch and carry, workers can herd turkeys into transport modules, a system associated with less bruising, injury, and stress. In a study published in 2000, three traditional turkey transport systems that require manual catching and loading were compared with a system that involves driving or herding the birds into transport crates. The researchers found that when the turkeys were not caught and carried, the birds had fewer bruises and injuries. Heart rate was used in this study as a measure of stress, and turkeys who were herded onto transport modules had lower heart rates after loading. With further study, this system is a promising alternative that could be more widely utilized in the turkey industry to improve the animals' welfare.[66]
Conclusion
Injury rates during catching and crating of slaughter-bound farmed birds in the United States are unacceptably high. Conventional manual catching of chickens and turkeys raised for meat can be hurried and rough, jeopardizing the animals' welfare. Of the alternatives to typical catching methods, manual catching of broiler chickens upright in pairs and herding turkeys into crates appear to be the best methods for ensuring the welfare of the animals during preparation for transport. If producers are unwilling to adopt the gentle manual catching method, chickens' welfare may still be improved by the adoption and proper operation of mechanical harvesters, though the model used and the level of training received by operators are important variables to consider. The practice of any catching method should be complemented by regular and routine auditing of bruises, fractures, and other injuries at the slaughter plant, and financial incentives to catching crews for careful animal handling.
[*] For more information, see "An HSUS Report: Welfare Issues with Selective Breeding for Rapid Growth in Broiler Chickens and Turkeys," "An HSUS Report: The Welfare of Animals in the Chicken Industry," "An HSUS Report: The Welfare of Animals in the Turkey Industry," and "An HSUS Report: The Welfare of Birds at Slaughter."
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[58] Ekstrand C. 1998. An observational cohort study of the effects of catching method on carcase rejection rates in broilers. Animal Welfare 7:87-96.
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[61] Personal correspondence with Charlotte Berg, Department of Animal Environment and Health, Swedish University of Agricultural Sciences, Skara, Sweden, February 12, 2009.
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[64] Kettlewell PJ and Mitchell MA. 1994. Catching, handling and loading of poultry for road transportation. World's Poultry Science Journal 50:54-6.
[65] Lacy MP and Czarick M. 1998. Mechanical harvesting of broilers. Poultry Science 77:1794-7.
[66] Prescott NB, Berry PS, Haslam S, and Tinker DB. 2000. Catching and crating turkeys: effects on carcass damage, heart rate, and other welfare parameters. Journal of Applied Poultry Research 9:424-32.
