When looking at how different housing systems protect the welfare of laying hens it is important to consider factors contributing to the hens' welfare, including whether hens are free to move; whether the system allows them to engage in behaviors that are normal for hens; whether they are protected from disease, injury, and predators; whether food and water are available in the appropriate amounts and type, and are of high quality; and whether the hens are handled properly.
Maintaining good welfare within housing systems usually involves trade-offs. For example, housing systems that allow hens to perform natural behaviors (e.g., nest building for laying hens) may, in fact, result in more challenges for disease and injury control. Conversely, improving disease and injury control by more intensively confining hens can limit the hens' freedom of movement and ability to engage in normal behaviors.
The chart below, which illustrates the welfare tradeoffs among housing systems for laying hens, is adapted and expanded from a chart included in the final report of the LayWel project (Welfare implications of changes in production systems for laying hens. See: www.laywel.eu/web/pdf/final%20activity%20report.pdf). More information about some of the items identified as welfare indicators is included on the next page of this document. Please be aware there are other indicators of animal welfare that are not included in the chart below; the point is simply to show that there are welfare advantages and disadvantages to every housing system.
Feather pecking1 = Feather pecking is an abnormal behavior in which birds damage other birds' feathers; most often it results from an inadequacy in the birds' environment. Feather pecking can include simply chewing on feathers or actually plucking them out. There are many contributors to feather pecking, including genetics, poor diet, infectious or parasitic diseases, and stress. Birds with damaged feathers have poor thermoregulation and greater energy demands than unaffected birds. If feather pecking is severe, bleeding may occur, which attracts even more pecking from other birds (cannibalistic behavior). Beak trimming is a common way to deal with excessive feather picking. Feather pecking and feather loss are greatly influenced by strain of bird, beak trimming, and epigenetic factors.
Cannibalism2 = The act of consuming tissues of other members of the same species, whether living or dead and at any stage of the life cycle; this is an abnormal behavior in laying hens. In laying hens, cannibalism may be directed toward different tissues, ranging from feathers to eggs, but the problem of most concern is pecking and tearing of the skin and underlying tissues and organs. If excessive, such behavior can cause hens to be severely injured or die. Cannibalism is greatly influenced by strain of bird, beak trimming, and epigenetic factors.
Bumblefoot3 = An inflammation and/or infection of the skin and connective tissues of the foot. The "bumbles" are really abscesses caused by the bacteria Staphylococcus aureus. Bumblefoot has been shown to be correlated to the use of wet or non-optimally designed perches or flooring.
Hen hysteria4 = A behavioral state characterized by extensive use of defense mechanisms and by a variety of clinical signs associated with high levels of fear, anxiety, restlessness, and general irritability.
Foraging = The act of looking or searching for food. Foraging behaviors are affected by the availability and type of food, as well as the availability and type of other substrates (e.g., litter, shavings).
Dustbathing5 = Involves tossing and rubbing dust between the feathers to maintain feather and skin condition.
1. Crespo R, Shivaprasad HL. Chapter 31–Developmental, metabolic, and other noninfectious disorders. In: Diseases of poultry, 11th edition. Ed: Saif YM, Barnes HJ, Glisson JR, et al. Blackwell Publishing. 2003;1055.
2. Newberry RC. Chapter 22–Cannibalism. In: Welfare of the laying hen. Ed: Perry GC. CAB International. 2004;239.
3. Tauson R, Abrahamsson P. Foot and skeletal disorders in laying hens: effects of perch design, hybrid housing system and stocking density. Acta Agric Scand, Sec A, Animal Science 1994;44:110.
4. Hurnik JF, Webster AB, Siegel PB. Dictionary of Farm Animal Behavior, second edition. Iowa State University Press, 1995.
5. Morton B. Improving the housing of laying hens to enhance welfare. Available at: http://vip.vetsci.usyd.edu.au/contentUpload/content_2727/MortonBriar.pdf. Accessed August 25, 2008.