Many people have read and commented on my previous post, where I tried to give some context to an animal activist video that attacked professional egg farmers in Canada. I have had numerous questions regarding housing types, and how “Welfare Friendly” they are. I am convinced that it would be easier to tell you how the colour purple smells. Anyways, here is a VERY BRIEF and superficial description of the welfare impacts of housing. These facts are based on scientific evaluations by some of the leading welfare scientists in the world. If you are “sciency”, I have included references at the bottom of the post, so I don’t get accused of making things up.
First, it is important to realize that animal welfare is generally evaluated under 3 sets of schemes.
1) Biological functioning measures an animal’s response to its environment. Mortality rates, production measures, corticosteroid levels, and any other measurable parameter will fall under this scheme. Welfare is assessed by the ability of the animal to adapt to its environment, and if it can adapt successfully, the welfare is felt to be good. For example, if you have a hen in a barn with a temperature of 15 degrees C, and her cortisol levels are normal, she is not ill, etc, etc, then you would say she is able to adapt to that environment, and her welfare is good. If she is in a 5 degree C barn, and her stress hormones are high, her body temperature is below normal, etc, you would say she cannot adapt to that temperature, and her welfare is poorer.
2) Affective state refers to the feelings of the animal. It is the feeling of hunger that is the problem, not the fact that the animal is hungry. Fear, frustration and boredom are important considerations in this approach, regardless of the physical state the animal is in. One caution with this approach is that affective states are extremely difficult to measure directly. Affective states can only be inferred from the actions the animal takes. For example, a shivering dog may be said to be cold, but she may actually be nervous, or excited.
3) Natural Living. The premise of this approach is that behavior evolves in a method similar to physical characteristics, and that extraneous behaviours will be phased out because they are too costly for the animal to maintain, if it is not important to the survival of the animal. Thus, any behavior, drive or urge that remains must be important to the animal, and for good welfare, the opportunity to perform all natural behaviours is necessary.
The welfare effects of different housing systems for laying hens are complicated and multi-layered. Conventional cages are heavily criticized because they severely restrict behavior and movement. They do provide many welfare advantages as well.
Typical modern conventional cage
Cages provide excellent health and environmental benefits for the hen. They also effectively control group size, resulting in less inter-bird aggression and cannibalism. Health advantages provided by cages include less viral and bacterial infections, less parasite infestations, less bumblefoot, lower mortality and less antibiotic usage than loose housed or aviary flocks. Hens in cages also have less competition for feed and water. Environmental benefits delivered by cage systems include the lowest ammonia and respirable dust levels. On the downside, cages predispose hens to metabolic imbalances such as osteoporosis and fatty liver. Osteoporosis increases the risk of fractures during handling at depopulation. It is assumed that fear and boredom are inevitable consequences of barren environments, and natural living is very poorly provided.
Furnished cages are larger cages that contain perches, nest boxes and a scratch pad that has substrate on it to encourage
A Furnished Cage in Ontario
dust bathing. Mortality rates and bone strength are improved over conventional cages, and this housing system results in the least fractures overall. Infection rates, aggression and cannibalism are the same as conventional cages. Foot infections are more prevalent in furnished cages than conventional cages. Affective states in furnished cages are improved over conventional cages because of the variety of activities and social interactions that hens can perform, reducing boredom. Natural living aspects are improved due to the ability to perch, dustbathe and lay eggs in a nest, but is still very limited.
Loose housing systems (aka floor barns, or free-run barns) provide hens with a much expanded repertoire of behavioral
A free run barn in Ontario
abilities, allowing hens to lay eggs in a nest, dustbathe, and forage. Hens are motivated to perform all of these behaviours, although to differing degrees. The barn in the picture has perches, although not all do. Aggression is higher in this housing system, and bone fracture incidence is around 60%. Ammonia and dust levels are high, with levels that are 3-4 times that of aviaries. Affective states are extremely variable, heavily dependent on the rank of the hen in the social hierarchy. The affective states are generally thought to be better overall than conventional cages. Natural living is improved over cages, due to the ability to nest and perch, but still limited.
Aviary housing is a system in which the hens are free in the barn and can access different levels throughout the barn. This system results in the best bone strength, but perversely the highest number of fractures, with up to 85% of the hens
An Aviary Barn in Ontario
getting a broken bone by the end of the lay cycle. Aviaries provide the widest repertoire of behavior, and the various heights allow submissive hens to escape effectively, and thus aggression is reduced from free-run barns. Ammonia and respirable dust are intermediate between cages and free-run, with levels 5-7 times that of cage barns. Affective states are assumed to be better than free-run barns, due to decrease in aggression and the thus fear, but are still dependent on social hierarchy. Natural living is improved over free-run due to the ability to fly, and perch in high sections of the barn.
Free range flocks have the ability to go outside. The range may be associated with a free-run barn, an aviary, or no permanent structure, only a mobile shelter to provide food, water and shelter. In Canada, free ranging can only occur during times of the year when the weather is reasonable. For several months of the year, the flocks are essentially free-run or aviary flocks, since going outside in the winter is not practical. Chickens in this type of housing have the ability to explore, experience weather and natural light and perform all their natural behaviors. These behavior benefits come at the cost of increased mortality, increased infections, predation and poor environmental control, resulting in thermal stress and discomfort from poor environmental condition such as mud and rain. Affective state is very good due to the ability to control her destiny, and make choices. Natural living proponents assess this housing system as far superior due to the range of natural behaviours it enables.
On top of all the considerations inherent in the physical layout of each housing system, the ability of the farmer to manage each barn can overcome many of the welfare differences between the systems. A well-managed cage barn will provide better welfare than a poorly managed aviary. The reverse is also true.
It is obvious that the three paradigms for evaluating animal welfare are often at odds with each other, and that each housing system satisfies each scheme to a greater or lesser extent. The housing system that provides the best welfare depends on the priority you place on each of the ways of measuring welfare. If natural living is the most important priority to you, cage systems will never be considered good providers of animal welfare. If you feel that it is preferable for the hens to be bored, rather than at greater risk for illness and dying, cages provide unparalleled welfare advantages. The relative importance of each area of welfare assessment is a philosophical decision that varies from person to person.
Add to this the impact that different housing systems have on food safety, egg quality, economics and the environment, and it is staggeringly complicated to compare the benefits of each housing system. It is far too simplistic to state that any housing system is inherently better than another, let alone that any of them are unacceptable or ideal. Anyone who can make this type of declaration likely doesn’t appreciate the complexity of the issue.
Mike the Chicken Vet
Tauson, R. Management and housing systems for layers- effects on welfare and production. World Poultry Science Journal 2005;61:477-490.
Lay , D.C., Fulton, R.M., Hester, P.Y., Karcher, D.M., Kjaer, J.B., Mench, J.A., Mullens, B.A., Newberry, R.C., Nicol, C.J., O’Sullivan, N.P., Porter, R.E. Hen welfare in different housing systems. Poultry Science 2011;90, 278-294.
Rodenburg, T.B., Tuyttens, F.A.M., Reu, K.D., Herman, L., Zoons, J., Sonck, B. Welfare assessment of laying hens in furnished cages and non-cage systems: an on-farm comparison. Animal Welfare 2008;17, 363-373.
Sherwin, C.M., Richards, G.H., Nicol, C.J. Comparison of the welfare of layer hens in 4 housing systems in the UK. Brit Poultry Science 2010;51, 488-499.
Wilkins L.J.,McKinstry J.L., Avery N.C., Knowles T.G., Brown S.N.,Tarlton J., Nicol C.J. Influence of housing system and design on bone strength and keel bone fractures in laying hens. Veterinary Record 2011;169:414-421.
Nimmermark, S., V. Lund, G. Gustafsson, W. Eduard. Ammonia, dust, and bacteria in welfare-oriented systems for laying hens. Annals Agricultural Environmental Medicine 2009;16:103-113.