Laying Hen Welfare in Australia

I. INTRODUCTION

In accepting the invitation to present a paper on laying hen welfare at APSS 2021, I thought that I would provide an overview of a special issue of Animal Production Science on layer hen welfare that will be published in early 2021. This special issue consists of 19 review papers on the welfare implications of: the production system; development, growth and production; husbandry and behaviour; and health. I had planned to report on the main findings of the authors and their recommendations on industry adoption and future research. However, this is too ambitious for APSS 2021 since such a report on the main findings and recommendations arising from 19 papers is beyond the length of either an oral or written presentation. Therefore, my aim with this paper is to first, briefly introduce the special issue papers (titles and authors) and second, focus on highlights (findings and recommendations) in the special issue that address three contentious welfare topics in the egg industry: animal welfare assessment; housing systems; and ‘natural behaviours’ and injurious behaviours.

II. 2021 SPECIAL ISSUE OF ANIMAL PRODUCTION SCIENCE ON LAYER HEN WELFARE

A group of Australian researchers with a wide discipline interest and expertise in poultry science were commissioned by Australian Eggs Limited to undertake a comprehensive independent review of the scientific literature on layer hen welfare. The objective of the series of reviews was to inform both current welfare discussions and future investment in welfare research and development in Australia. In considering their recommendations, the reviewers reflected on the context of egg production in Australia. This consideration of the characteristics of Australian egg production is very relevant since a considerable amount of the research on laying hen welfare has been and continues to be conducted by European researchers and thus is most relevant to European conditions and production systems. As Fraser (2008) stated “To date, animal welfare science has tended to be a somewhat Eurocentric field. Much of the work has been done on production systems typical of agriculture in Europe and countries with European-derived culture, and the direction of some research has been influenced by actual or potential European regulations.”

Nineteen review papers will be published in this special issue of Animal Production Science on layer hen welfare. The abbreviated titles, authors and the general subject area are presented in Table 1.

Table 1 - Abbreviated titles, authors and the general subject area of the review papers that are to be published in 2021 in the special issue of Animal Production Science on layer hen welfare.

III. ANIMAL WELFARE ASSESSMENT

a) Review findings

Accurate assessment of animal welfare is crucial in understanding how laying hens should be housed and managed to achieve best practice animal welfare. According to our current conception, welfare is a state within an animal, and most directly relates to what the animal itself experiences (Mellor et al., 2009).

Animal welfare assessment is a topic of some debate, particularly in the public but also to a lesser extent in the scientific community. There is no single measure or indicator of welfare and the assessment of animal welfare currently uses a variety of measures, particularly behavioural, physiological and fitness measures. Although animal welfare science has made major contributions to understanding animal welfare and its assessment, often by the use of multiple indicators from multiple disciplines, their relative importance has yet to be clarified (Fraser 2008; Nicol et al., 2011; Hemsworth et al., 2015; Sandoe et al., 2019). The use of only one or several of these indicators of animal welfare provides a less holistic view of the animal’s welfare state.

Several review papers in the special issue of Animal Production Science on layer hen welfare consider in some detail animal welfare assessment (papers 1, 9 and 10, Table 1). A number of papers also consider the main hen health problems in the Australian egg industry, their welfare implications and their prevention (papers 8, 9, 15, 16, and 17, Table 1). The main findings and recommendations from these review papers are summarised here.

The majority of the welfare studies conducted on farm animals, including laying hens, have employed what is often called the biological functioning framework. The rationale for this framework is that difficult or inadequate adaptation generates welfare problems for animals and that suboptimal biological functioning accompanies negative affective states, such as fear, pain, sickness, hunger, thirst, helplessness and frustration. In assessing risks to animal welfare, extreme coping attempts are measured using behavioural and physiological stress responses, as well as health and other fitness variables. Many of the review papers in the special issue of Animal Production Science on layer hen welfare refer to these indicators when considering risks to hen welfare. The most common physiological measure in laying hens is circulating corticosterone concentration (or its metabolites in eggs, excreta, feathers), and measures of immune function, such as heterophil to lymphocyte ratio and packed cell volume, are often used. Abnormal behaviours, such as pacing, feather, object and cohort pecking, and head shaking, are also commonly used to study hen welfare.

Flock mortality is one of the most important animal welfare indicators for laying hens. As with disease, the implications of the noxious subjective experiences associated with mortality on animal welfare are not always recognised by the public or some non-government organisations. Health and injuries are an important part of welfare and whenever an animal is injured or diseased, welfare is poorer. Similarly, hypothermia, hunger, thirst, sickness and pain associated with mortality are considered potentially noxious affective (subjective) experiences.

In addition to health, stress can have significant biological costs, leading to growth and reproductive impairments, which may reflect and/or result in welfare problems for the animal. Fitness measures studied in laying hens include bodyweight, feed conversion, hen day production, condition of the skin and plumage, keel-bone damage, foot health score and mortality.

Since what the animal experiences is central to understanding animal welfare, the conceptual framework often called the affective state framework, emphasises that the welfare of an animal derives from its capacity for affective (subjective) experiences. Motivation tests involve ‘asking’ the animal whether it will work (perform some arbitrary task such as pecking a key or pushing a door) to obtain something it wants or wants to do (positive reinforcers leading to a positive affective state) or of avoiding something it does not want (negative reinforcer leading to a negative affective state). For example, motivation tests have been used to measure the value that laying hens place on accessing a nest box for oviposition, substrates for foraging and dust bathing, and perches for roosting.

Only a few studies have utilised both these frameworks in studying hen welfare, that is examining both the choice behaviour of laying hens and the biological functioning consequences of depriving laying hens of this opportunity (e.g., Nicol et al., 2009; Engel et al., 2019).

b) Review recommendations

Some of the key recommendations from authors of reviews in the special issue of Animal Production Science on layer hen welfare are as follows.

In appreciating the impact of housing, management and husbandry practices on hen welfare, it is important to understand (1) how motivated they are to choose an environmental option or perform a type of behaviour or avoid an environmental or husbandry option and (2) the consequences of depriving them of their choice on behavioural and physiological stress responses as well as fitness variables, including health.

However, there remain substantial gaps in our understanding of stress in laying hens. In particular, a major gap exists with respect to understanding the regulation of physiological stress responses. A sound understanding of this is required in order to assess physiological stress and its impact on normal physiological and behavioural functioning.

The public is a key driver of animal welfare change and thus there needs to be a clear articulation of the effects of housing, management and husbandry practices on hen welfare. Since the welfare consequences arising from illness, injury and mortality are often not well recognised, a more effective communication between government, industry and the public sectors would benefit from a better informed public on the full array of behavioural, physiological and fitness measures used by researchers in examining the effects of industry practices on hen welfare.

IV. HOUSING SYSTEMS AND LAYING HEN WELFARE

a) Review findings

The main concerns that the public has about animal production appear to focus on the conditions that guarantee food security, public health, environmental quality and animal welfare (Vanhonacker et al., 2012). In relation to animal welfare of farm animals, it is a controversial topic for many, particularly because of the perceived negative effects of intensification of animal production on the animal, such as a general lack of social contact, a general lack of space, an inability to exercise, ‘barrenness’ of the environment, abnormal behaviour and the reliance on technology (Barnett et al., 2001; Te Velde et al., 2002; Fraser 2005, 2008; Vanhonacker et al., 2009; Hemsworth, 2018). In contrast, farm animal welfare problems in extensive systems, such as problems with extreme cold and heat, parasites, and poor access to feed and water, have received less attention (Fraser 2008).

Several review papers in this special issue of Animal Production Science consider one or a number of the three main housing systems, cage, barn and free range and the design and management of these systems (papers 1, 2, 3, 10 and 11, Table 1). The main findings and recommendations from these review papers are considered here.

Comparisons of housing systems, particularly in commercial settings, are complex because of potentially confounding differences in physical, climatic and social environments, genetics, nutrition and management. Furthermore, some of the confounding factors are inherent to some specific housing systems.

Nevertheless, research in commercial and experimental settings comparing housing systems generally indicates that hens in conventional and furnished cages have lower (or similar), but not higher, levels of stress based on glucocorticoid concentrations than hens in non-cage systems. Furthermore, caged hens generally have lower mortality rates with less variability than hens in non-cage systems. However, the behavioural repertoire of laying hens housed in conventional cages is clearly more compromised than those hens in non-cage systems. Abnormal behaviours, such as pacing, feather pecking, spot pecking and head shaking, are commonly seen in barren production environments and clearly the use of enrichment in indoor systems requires ongoing research.

In contrast to conventional cages, furnished cages provide opportunities for perching, dust-bathing, foraging and nesting in a nest box, activities that may elicit positive affective states in laying hens. While hens may prefer to distance themselves from other birds, their strength of motivation to do so has not been thoroughly investigated and appears to depend on the activities in which hens are engaged.

Barn systems in Australia are indoor with single-level (flat deck) or multilevel housing (aviary). These systems offer hens freedom of movement and an opportunity to display a repertoire of behaviours. Barn systems in comparison to free-range systems offer better biosecurity due to lack of direct access to wild birds and their faeces. In addition to protection from predators, barn systems also offer protection from diseases and possibly parasites that can be contracted from range areas. However, injurious behaviours, such as feather pecking and cannibalism, can occur, as well fractures and injuries arising from collision or falls from elevated structures. Barns generally have poorer air quality (dust and NH3 concentrations) and thus greater compromised hen health and welfare than cage systems.

Housing in free-range systems are either single-level (flat deck) or multilevel (aviary). The majority of hens in free-range systems access the range, spending most of this time foraging outside. Use of the range will depend on the range design but may also depend on the indoor shed design, and this is currently not well understood. Range access appears to be associated with some health benefits such as improved plumage condition and reduced footpad dermatitis, but there are also health risks associated with free-range systems such as greater susceptibility to disease (e.g. spotty liver disease), heat stress, predation, and potentially parasites in comparison to barn or cage housing systems. Design of the range area, indoor shed, management practices and rearing environments can all influence how hens utilise free-range housing systems.

Although feather-pecking is multi-factorial in its aetiology, in general loose-housed hens are more susceptible to feather pecking and cannibalism outbreaks as it spreads more easily between the large numbers of hens housed in contact with each other. Smothering, in which hens press tightly together and often on top of each other in such a way that results in death, is mainly reported in non-cage systems. Anecdotal reports suggest that smothering can account for a considerable proportion of mortality in Australian free-range systems, but its aetiology is poorly understood.

While not always fully appreciated by the public and some non-government organisations, management decisions markedly affect laying hen welfare, irrespective of the housing system. At the level of farm management, human resource-management practices, including employee selection and training, and animal management practices, such as best practice in housing and husbandry, and implementation of welfare protocols and audits, all affect hen welfare. At the stockperson level, together with the opportunity to perform their tasks well, stockpeople require a range of well-developed husbandry skills, knowledge and willingness (motivation and attitudes) to effectively care for and manage laying hens.

b) Review recommendations

Sustainability of the production system will depend on animal welfare legislation, public and consumer preference, cost of production, environmental footprint and suitable hen genetics. Research on housing systems highlights the importance of the design of the housing system and management of the system: multiple management and system design factors will affect how hens adapt to the housing environment and the subsequent impacts on their welfare.

Space is a contentious issue for many and while floor space per laying hen is generally less in cage systems, the lack of a suitable site or resource for activities such as nesting, pecking and scratching a suitable litter substrate, dust-bathing and perching also restricts the behavioural repertoire of hens in conventional cages.

Furnished cages provides opportunity for nesting, foraging, roosting and dust-bathing. Some authors have suggested that the behavioural needs for these behavioural activities are not fully satisfied in furnished cages; however this requires testing. Our understanding of the strength of motivation of hens to distance themselves from other birds based on the specific behavioural activities that they are engaged in, is poor. A better understanding of the effects of floor space and group size on hen welfare in furnished cages is therefore recommended.

The multi-tier provision of an aviary structure in a barn system offers increased total useable surface and allows hens to disperse across several levels of living space. However, one of the major health and thus welfare concerns in barn systems (and aviaries in free-range systems) is the high incidence of fractures. Good design, placement and management of structures in the shed can help mitigate these to a large extent. Pullets should also be reared in housing systems that offer platforms, tiers and perches that train them to go up in a system to reach food and water. Genetics may also influence the use of space and distribution within an aviary. The other major concern in barn systems as with free-range systems is the prevalence of severe feather pecking. Although feather pecking is multi-factorial in its aetiology, in general loose-housed hens are more susceptible to feather pecking and cannibalism outbreaks.

The majority of hens in free-range systems access the range. The use of the range is associated with the range design, but may also depend on the indoor shed design, which is currently not well understood. Ranging may have some positive effects on welfare, but this needs to be further validated across commercial farms. Research is also required to better understand how pullet rearing strategies may affect adult range use. Mortality due to smothering is mainly reported in non-cage systems and research on its aetiology in Australian free-range systems is required.

V. ‘NATURAL’ BEHAVIOURS, INJURIOUS BEHAVIOURS AND LAYING HEN WELFARE

a) Review findings

In contrast to indoor housing, outdoor housing is typically extensive and, so, is considered by some to be inherently ‘good’ because it provides a more ‘natural’ environment and choice for the animal in performing several behaviours over a larger area, and the lower technological inputs provide for fewer equipment breakdowns that may adversely affect welfare (Hemsworth, 2018). Furthermore, some have suggested that the problems with modern animal production is not that the animals are unable to perform certain behavioural opportunities, but they are unable to fill the extra time available with limited behaviours when they have no need to find food, water, or shelter (Fraser 2005).

A common view amongst the public and some non-government organisations is that the provision of ‘natural’ aspects in the animal’s environment and the ability for the animal to perform its full ‘behavioural repertoire’ equates to safeguarding its welfare. However, as many authors have recognised, encouraging captive animals to perform all the behavioural patterns evident in the wild does not necessarily safeguard animal welfare because many of these patterns in the wild may be responses to adversity, such as shivering in harsh weather and fleeing from predators (e.g. Fraser 2003; Dawkins 2008; Mason and Burn 2018). Furthermore, while many of the ‘wild’ behaviours are perfectly natural, their absence in captivity should not necessarily raise welfare concerns because they are elicited by external stimuli or physiological states that have already been fulfilled in animals whose safety, physical, social, health and nutritional needs are met (Dawkins 2008).

A number of papers in the special issue of Animal Production Science review hen behaviour in relation to hen welfare (papers 1, 2, 3, 10, 11 and 12, Table 1) and the main findings and recommendations from these papers are considered here.

Preference and motivation research indicates that laying hens value resources such as substrates for foraging and dust bathing, perches for roosting and particularly nest boxes for oviposition. Hens are generally motivated to dust bathe, but in contrast to nesting, the results of studies on the strength of motivation to access a dust-bathing substrate are conflicting. However, there is no convincing evidence that deprivation of any of these resources in inexperienced hens results in physiological stress. Furthermore, apart from adverse effects of the absence of perches on bone strength, there is no evidence that deprivation of nest boxes, perches, and foraging and dust-bathing substrates results in reduction in fitness such as reduced egg production or health. Nevertheless, preference research indicates that the opportunity to utilise these resources, particularly nest boxes, may elicit positive affective states in laying hens.

The behavioural repertoire of commercial laying hens, particularly when housed in conventional cages, is compromised and, together with barren environments, caged housing systems have been implicated in the development of so-called abnormal behaviours in laying hens, such as pacing, feather pecking, spot pecking and head shaking. While most of the enrichment studies have specifically examined feather pecking, further research is required to examine the implications of environment enrichment on other abnormal behaviours and welfare in laying hens, particularly in cage systems.

Feather-pecking behaviour has been identified as one of the most significant welfare concerns for laying hens, due to its high frequency of occurrence and damaging nature. Although feather pecking occurs unpredictably in all housing systems, severe feather pecking in non-cage systems is more problematic due to the greater difficulty of intervention. Feather pecking is multi-factorial in its aetiology and challenging to eliminate, but there is evidence that alternative pecking opportunities, such as litter substrate and additional enrichment (such as straw and grain in litter, sand and peat straw in baskets, maize and pea-barley silage, deeper litter and strings) both during rearing and in adulthood, can reduce the development and prevalence of feather pecking.

There is also evidence that some complexity and, thus, stimulation during rearing and adulthood reduces fearfulness in laying hens. Furthermore, exploratory behaviour is regarded as a pleasurable activity in itself and, thus, the opportunity for exploration may be associated with a positive affective experience in laying hens.

b) Review recommendations

In contrast to indoor housing, outdoor housing is typically extensive and so is considered by some to be inherently ‘good’ because it provides a more ‘natural’ environment and choice for the animal to perform an extensive range of behaviours over a larger area. However, this concept of natural is usually too poorly defined to provide a sound basis for animal welfare assessment, and indeed when applied uncritically it may lead to poorer welfare instead of an improvement. Although the concept of natural living does not provide a rigorous basis for welfare assessment, it usefully draws attention to the potential welfare benefits of providing opportunities to engage in natural behaviours, such as nesting, perching and foraging.

Further research is required on the aetiology of severe feather pecking. Common recommendations in the literature to prevent or control severe feather pecking include stimulating feeding and foraging behaviour by providing high-fibre diets and suitable litter from an early age onward, controlling fear and stress levels through genetic selection, reducing stress and improving the stockmanship skills of the stockperson, but clearly further research is required. Further research is also required to examine the implications of environment enrichment on other abnormal behaviours and welfare in laying hens, particularly in cage systems.

VI. CONCLUSION

Many of the public concerns and policy debates about farm animal welfare, including laying hen welfare, have generally focussed on intensive housing systems. This focus on housing systems has distracted research, development and education from some of the other important considerations in safeguarding and improving animal welfare. Indeed, the design and management of the housing system as well as the husbandry skills, knowledge and willingness of stockpeople to effectively care for and manage laying hens is generally more important for animal welfare than is generally recognised.

The public is a key driver of animal welfare change and thus there needs to be a clear articulation of the full array of behavioural, physiological and fitness measures that researchers utilise to examine the effects of industry practices on hen welfare and their findings.

Presented at the 32th Annual Australian Poultry Science Symposium 2021. For information on the next edition, click here.