Which poultry system is better for poultry health and welfare?

Which poultry system is best for poultry health and welfare? This is definitely the billion dollar poultry system question, as it were.

A comparative study of poultry systems suggests that free range system is best for poultry health and welfare. We agree, in a previous article we rated free range as best for poultry welfare. But now we have some data making our case, have a read and let us know what you think.

Multiple factors in a poultry system determine chicken health and welfare outcomes. For instance, limited movement increases risk for skeletal fragility. Moreover, overcrowding increases risk of disease spread, cannibalism and stampeding.

In this article we summarize a study by Lay Jr. et. al. In said study Lay Jr. and co, compared conventional cages, furnished cages, noncage systems, and outdoor systems. According to them, each poultry system has its own unique set of animal welfare challenges. No system is perfect from a hen welfare perspective.

Inescapably, in order to select the most suitable poultry housing to implement in your farm, apply due diligence when comparing all applicable options. In our previous article, we think biosecurity and animal welfare are key factors in determining the best poultry system.

Careful management of a poultry system is necessary for best animal welfare outcomes. Certainly, any poultry system if mismanaged can turn out to be the worst in terms of health and welfare outcome. Therefore, a balance of housing design, breed, rearing conditions, among other factors are all essential for optimal outcome.

Aspects of poultry health determined by poultry system

There are several aspects of poultry health that are determined or affected by poultry housing. Lay Jr. and co. list the following:

• Mortality
• Disease susceptibility
• Skeletal and foot health
• Pest and parasite load
• Behavior, affective states or temperament
• Stress
• Nutrition
• Expected behavioral expression
• Genetics

In summary, these factors and many more determine the general health of chicken in a specific poultry system. Consequently, all 8 poultry housing systems determine poultry health to varying degrees.

Poultry system grouping

In their study, Lay Jr. et. al. were basically comparing litter based poultry systems against cage systems.  Litter based systems consist of two poultry systems, namely: aviary and deep litter.

On the other hand, cage systems refer to both traditional or conventional cage and enriched or furnished cage systems. Further still, Lay Jr. et. al. have mentioned soil based systems, which refers to extensive poultry systems where birds are in contact with soil.

Findings

We are yet to find such a comprehensive study as this one by Lay Jr and co. However, for the purpose of this article we will only cover aspects that we think will be of interest to you as a poultry farmer.

That being said, we will also steer clear of content that we find too technical or scientific. Of course, if you are interested, check out the full study from the link providing at the beginning of this article.

1. Mortality

One of the key indicators of poultry welfare and health is mortality. Essentially, high mortality can be an indicator that welfare and health aspects are low, and vice versa. Below are the main points on mortality from the study.

Cannibalism occurs in both caged and non-caged systems. Notably, cannibalism and feather pecking were reported as the main causes of mortality in commercial hens.

Mortality is generally greater in laying hens raised in deep litter and aviary systems in comparison to hens in furnished cages.

Data collected from commercial farms showed that mortality differed significantly between non-cage, outdoor, conventional cages and furnished cage systems. However, mortality rates in furnished cages were significantly lower than in any other system.

A 4 year Scandinavian study on laying hens reported highest mortality rates in litter based and free range systems in contrast to conventional cages.

2. Disease

According to Lay Jr. et. al., Bacterial infections were the most common cause of mortality in birds raised on litter based systems. These included erysipelas, colibacillosis, and pasteurellosis.

Moreover, hens raised in litter and free range systems had higher mortality associated with viral diseases in contrast to hens in conventional cages. Examples of such viral diseases included lymphoid leukosis, Marek’s disease, and Newcastle disease, coccidiosis and red mites.

Hens in deep litter systems are particularly at increased risk of erysipelas when compared to hens in cage systems.

Several infectious diseases in hens are the outcome of contact with soil, litter and fomites such as rodents, beetles, and equipment carrying those disease agents.

Histomoniasis is generally associated with soil contact and affects free range hens. Additionally, the soilborne microogarnism – erysipelothrix rhusiopathiae – affects hens exposed to litter and soil at higher rates.

Respiratory diseases / Air quality

Poor air quality in a poultry system can result to the accummulation of aerosolized dust and bacteria. In effect, high dust concentrations have been linked with increased mortality. 

Air quality issues have been notably higher in litter based systems in contrast to cage systems. Generally, cage systems have significantly lower aerosolized inhalable and respirable dust particles than litter based systems. According to Lay Jr. et. .al. this may partly explain why deep litter hens have higher bacterial disease rates than hens in cage systems.

3. Skeletal health

Hens can suffer a number of skeletal issues as a result of the housing system they are housed in. For example these include osteoporosis, cage layer fatigue, and keel bone deformities. 

Osteoporosis is a noninfectious condition caused by age related decrease in mineralized structural bone. Effectively, it results to skeletal fragility and susceptibility to fracture.

Nowadays osteoporosis is widespread in commercial hens and contributes to 20 – 35% of all mortalities during egg production cycle of caged hens. Furthermore, in severe state, osteoporosis is referred to as cage layer fatigue.

Cage layer fatigue causes bone brittleness, paralysis, and death in hens. It is characteristic to hens in cage systems, as the name suggests. However, cage layer fatigue is increasingly the outcome of malnutrition: inadequate nutritional intake and absorption of calcium, or metabolites of vitamin D.

In contrast to non cage systems, skeletal health issues are the result of lack of exercise in hens in cage systems. In effect, hens in deep litter and slatted floor systems had higher skeletal health than hens in cage systems.

“Hens housed in a single-level noncage system with a floor of either deep litter or raised wire (manure pit below) had similar bone strength, whereas hens in conventional cages had lower bone strength, suggesting that skeletal quality was not influenced by the wire flooring but instead by hen activity”

Notably, raising pullets in deep litter then moving them to cage systems for egg production purposes had a negative effect on their skeletal health.

Skeletal integrity

According to Lay Jr. et. al. skeletal integrity is rated as poor in all poultry systems except furnished cages. Hens in conventional and furnished cages have overall better foot health than hens in litter and range based systems. 

Old bone fractures

Caged hens however have lower occurrences of old fractures. Old skeletal fractures are concern in regards chronic pain. Notably, incidences of old keel breaks in noncage systems range from 52 – 73%. This is highly attributed to increased activity during movement from litter, to raised slats or when access to nesting boxes. 

Perching injuries

Perches can result to both good and bad outcomes. For instance, while they improve skeletal strength, landing failures can result to fractures. High use of perches can result to keel bone deviations. Strategic arrangement of multi-level perches is required in order to reduce injuries and increase successful landing.

Depopulation injuries

In contrast to hens in extensive systems or furnished cages with wider door openings, high rates of fractures occur in hens in conventional cages during depopulation and transport. Housing systems that allow for easier removal of birds decrease bone breakage.

Importantly, gentle handling of chicken – by 2 legs instead of 1 – during depopulation reduces bone breakage.

4. Foot health

Footpad dermatitis, bumblefoot, hyperkeratosis, and excessive claw growth are the most common foot issues in hens.

Footpad dermatitis can be caused by wet litter conditions and high ammonia content in litter. The condition is characterized by lesions in the footpad; an inflammation of the cutaneous tissue. 

Furthermore, if footpads become infected by bacteria, the condition can result to bumblefoot, a localized bulbous lesion of the ball of the foot.

Hyperkeratosis – a high wearing out of the corneus layer of the skin – occurs in the toe and footpads of hens in caged systems. However, incidences of hyperkeratosis are significantly are lower in furnished cages than in conventional cages.

In effect, Hyperkeratosis is caused by increased compression load of toe or footpad on the wire floor of cage systems and perches. 

Excessively long claws can break off easily and result to open wounds, bleeding and infections. Excessive claw growth results from the lack of abrasive materials for trimming nails. Deep litter systems afford scratching and thereby minimize excessive claw growth. Claw health is low in conventional cages.

5. Pest and parasite load

Poultry pests include flies and beetles that develop in accumulated manure or feed, as well as several ectoparasites. Conventional cages, and even furnished cages or floor operations can encourage accumulations of manure and manure-feed mixtures.

High density open-style or deep pit conventional cage systems are most prone to fly problems due to accumulated manure than cage systems with manure belts.

Issues associated with beetles occur via the consumption of possibly of pathogen contaminated beetles, or by beetle damage to insulation. Since they’ve long lifespans, pathogen carrying beetles can remain in poultry systems for a long time. Generally, low stock populations enable manure drying and lessens issues with flies and potentially also beetles.

Deep litter and range birds potentially control flies and beetles by scattering litter and eating respective pest. In effect, conventional cage systems are most at risk from flies and beetles. Furnished cage score in the median while non cage systems have lowest risk. Additionally, risk of beetle consumption by birds and potential consequential transmission is probably highest in noncage systems, which are liable to producing very high beetle populations in litter near water and feed lines.

Ectoparasites

Ectoparasites are categorized into nest dwelling and permanent categories. Blood feeding mites – Dermanyssus and Ornithonyssus – can cause health issues including irritation, blood loss, and metabolically exhausting immune response. Furthermore, mites can carry other poultry disease causing pathogens.

Nest dwelling ectoparasites live in poultry housing but find their ways to birds during their life cycle. Red mite, soft ticks and certain fleas are common examples of such parasites. Generally, the more complex a housing system, the greater the expectation of ectoparasites. In comparison, slatted floor systems which have relatively sterile surfaces do effectively control ectoparasites.

However, highly dense hen populations in slatted floors enable rapid reproduction and spread of permanent ectoparasites, notably the nothern fowl mite and the body louse. Additionally, beak-trimmed hens in slatted floors harbor at least 3 – 10 times more ectoparasites than undebeacked hens. This is attributed to impaired feather grooming ability.

The order of risk to ectoparasites by housing system, from high to least, can be noncage, furnished cage, and conventional cage.

6. Expected natural behaviors

The extent to which adult hens exhibit the expected array of natural behavior depend on a number of factors. These include housing type, genetics, previous experience, and so forth. Welfare concerns arise if housing type limits such behaviors, resulting to distress or aggression (such feather pecking) and hysteria.

Conventional cages

Movement, and related physiological activity is significantly restricted for birds in conventional cages, although cage size and stock density do play part.

High stock density can cause plumage damage and make access to feed and water difficult. Furthermore, high stocking can result in increased of  feather pecking, cannibalism and smothering. These behaviors are usually addressed by beak trimming.

In some strains, hens lower in pecking order may suffer malnutrition when dominant hens guard feeders with aggression and prevent sufficient feeding by others.

Conventional cages lack appropriate material that stimulate ground pecking and scratching, behaviors that trim claws and beaks naturally. Overgrown claws can result to bird trapage.

Sham dust bathing –  where birds simulate dust bathing behavior on wire floor – can also occur in some breeds. Lack of proper dust bathing results to a dirtier plumage, that is less waterproof and less insulative.

Additionally, the lack of a nesting boxes can result to frustration.

Caged hens do not exhibit broodiness partly because of genetic selection, and due to lack of access to eggs as they are extracted as soon as they are laid.  

Furnished cages

Enriched cages a.k.a furnished cages, afford improved welfare by allowing some foraging, dust bathing, nesting, and perching. However, they still limit other behaviors such as flying and wing flapping.

Non cage systems

Non cage systems can be 100% slats or 100% litter floors.

A key feature of non cage systems is their affordance of sufficient space for bird engagement in a variety of behaviors. 

On the downside, cases of cannibalism and feather pecking can be high if hens are not beak trimmed. Large flock sizes contributes to cannibalism. Moreover, the behavior can spread within a flock through social learning.

Opportunities to forage in non cage systems can lower the risk of feather pecking and cannibalism. This however depends on the availability of quality litter and learning foraging behavior during rearing.

In spite of access to nesting boxes, some hens will still lay eggs on litter. 

Perching during rearing period has been attributed to lower aggression in a flock. Missed landings from high perches can lead to injuries and bone fractures.

Stocking density can have unpredictable outcomes. Low density flocks tend to cluster around key resources while high density flocks are evenly distributed in a coop. Clustering can promote to aggressive behaviors, in contrast when birds are evenly spread out.

Outdoor – free range -systems

Access to free range enables hens to experience more individual space when foraging. In addition, when outdoors, chicken also ingest grit, engage in dust bathing and get access to direct sunlight.

Depletion of vegetation can result to cannibalism and feather pecking, especially in large flocks.

Sheltering areas are also important when outdoors to provide shelter from strong sun, and rain. 

Presence of roosters can also have mixed outcomes. Their presence in a flock can reduce aggression. However, roosters can injure eggs and be targets of aggressive behaviors.

Non cage systems, especially free range, afford the engagement in diverse ancestral behaviors.

7. Non-Nutritional feeding

Pasture-based poultry systems afford access to a variety of nutrients. Moreover, access to pasture can be used as a means to lower feed costs, as long as care is taken to prevent malnutrition.

Access to both nutrient and non-nutrient material can affect quality of nutritions ingested and amount digested and absorbed.

Feeding on litter material – e.g. paper – can result to poor digestion and absorption of feed nutrients. In contrast, the ingestion of wood shavings increases feed digestibility.

8.Stress

Stress response is characterized mainly by the activation of 2 systems namely, the hypothalamic-pituitary-adrenal (HPA) axis and the sympathoadrenal (SA) axis.

Glucocorticoids and corticosterone measures can be used to measure the response of the HPA and SA axis. In general, low measures indicate low stress and vice versa. An enlarged adrenal gland indicates chronic stress.

Immune response is yet another measure stress. For instance, the ratio of heterophils to lymphocytes can be used to measure stress.

Welfare concerns during depopulation

Hens from non cage and outdoor systems were more stressed during depopulation, in contrast to hens from furnished cages. 

Furthermore, Lay Jr. and co noted that hen from cages with large doors were less stressed.   Amount of time and effort involved in catching birds were thought to be likely contributors. Overall, improved handling no matter the poultry system decreased measurable stress.

9. Affective states

Emotions such as happiness, sadness, fear, pain and anxiety are referred to as affective states. Affective states are another key factor to determining animal welfare.

Notably, emotions are accompanied by behavioral, physiological, and cognitive changes. For instance, frustration can occur on the insufficient engagement in certain behaviors such as nesting, dust bathing and so on.

Potential sources of pain in laying hens include injuries, health problems, human mishandling, disease, and beak trimming.

Notably, beak trimmed hens can later on suffer acute or chronic pain. 

10. Genetics

For this point, we will make a comment for two reasons. Firstly, we foresee a seismic shift away from cage systems in 5 years. Secondly, by then, and since Lay Jr. and co.’s study, new poultry breeds will have come to market.

As a result, new health and welfare studies have to be conducted. This has to happen in parallel with the development of newer breeds bred purposely for cage-alternative systems.