Free-range egg production: its implications for hen welfare

Additional keywords: behaviour, enrichment, individual, laying hen, range use.

Animal welfare in the livestock sector is a prominent issue across the world, including Australia. It is increasingly important to consumers, stakeholders and governments that the management of animals kept for food production ensures their well-being. An animal’s welfare is multi-faceted and can be defined in a variety of ways (Carenzi and Verga 2009). It encompasses all aspects of an animal’s biological functioning in relation to their surrounding environment. More recently, the five-domain model highlights that nutrition, environment, health, mental state (positive and negative) and behaviour should all be considered when evaluating an animal’s welfare state (Mellor 2017). One aspect of welfare, which typically resonates strongly with the general public, is the ability for animals to be able to perform natural behaviours. In the case of laying hens, more natural living is believed to be achieved through providing access to an outside area (Rohlf et al. 2019), which is the main characteristic of free-range housing systems (also called ‘pastured eggs’, and which may or may not be organic). Thus, the Australian egg industry continues to see an increase in free-range grocery egg sales with free-range sales holding 56% of the grocery market value, followed by caged eggs at 30%, and barn-laid eggs at 11%, as reported in the 2018–2019 financial year (Australian Eggs 2019). There is a strong public interest in the way these systems are managed (e.g. outdoor stocking density and the resulting change in egg-labelling legislation; Campbell et al. 2017a) and a concern for hen welfare (Moffat et al. 2019). Additionally, as consumers become more conscious of their own health, free-range eggs are perceived as healthier and tastier than caged eggs (Bray and Ankeny 2017). For instance, free-range eggs may contain higher vitamin A, D, and E concentrations (Karsten et al. 2010; Guo et al. 2017) but their composition highly depends on what forage is provided outdoors (Karsten et al. 2010).

Free-range housing systems are unique in that they provide higher environmental choice than controlled indoor systems (Larsen et al. 2018), with perceived increased opportunities to express natural behaviour. The hens have exposure to daylight, which can increase vitamin synthesis from sunshine, possibly explaining the higher vitamin D concentrations in free-range eggs (Guo et al. 2017). Their exercise levels may also be higher than in indoor loose-housed systems. However, all laying-hen housing systems have both benefits and risks and clear scientific evidence of precisely how hens fare in free-range housing systems is needed. This review summarises the literature on hen welfare in free-range systems, with a focus on results from Australian-based research, but includes international research conducted on brown layer strains where Australian-based research is lacking. The majority of the total Australian flock of laying hens (all types of housing systems) are located within the states of New South Wales (33%), Victoria (26%) and Queensland (25%; Australian Eggs 2019). Flocks may experience severe thunderstorms, 35°C+ temperatures, freezing temperatures, bushfires, floods, drought and tropical cyclones across these regions, hence representing a variety of climatic conditions. Range use by laying hens, hen behaviour on the range, factors that affect range use, and impacts of ranging on hen health and other aspects of welfare are discussed. Specific areas where more research is needed are also highlighted. Literature published within the past 10 years has been included preferentially as the rate of genetic change in strain selection may render dated research less relevant.

Free-range systems provide outdoor access, but the frequency and length of ranging varies among individuals. Traditionally, when visually observing the number of hens present on the range, simultaneous occupancy has been reported to be low (Hegelund et al. 2005; Nicol et al. 2003) and can vary greatly with time of day and among farms (de Koning et al. 2019a), leading to the now outdated conclusion that not many hens utilise this outdoor resource. More recently, the increasing use of radio-frequency identification (RFID) technology that allows tracking of individual hens has showed much higher range use. RFID systems can read microchipped leg bands of individual hens while, for instance, they are travelling in and out of the shed. This approach provides an accurate assessment of how long a specific hen spends outside and how often it transitions between the indoor shed and outdoor range (Hartcher et al. 2016; Campbell et al. 2017a; Larsen et al. 2017a). The systems can also include multiple sensors that are placed at different locations within the range area to track how far out onto the range hens venture (Larsen et al. 2017a). The systems provide valuable information on range access in experimental studies, although they are not yet financially or practically feasible for widespread commercial use.

Across both experimental (small flocks up to 150 hens/pen) and commercial Australian studies, the majority of hens access the range daily. Initially, only small numbers of hens venture outside when the pop-holes first open, and then ranging increases over the following days (Campbell et al. 2017a, 2018a, 2020). However, there is high variation among individual hens in the total time spent outside and the length of each range visit (Larsen et al. 2017a; Campbell et al. 2017a, 2018a, 2020). Additionally, within flocks, there are small subpopulations of hens that infrequently or never venture outdoors (Campbell et al. 2017a; Larsen et al. 2017a). Studies on both experimental and commercial flocks conducted within Australia have shown association between range access and personality type, by using various behavioural tests. Not every test has shown differences, but, in general, hens that use the range infrequently or not at all show higher fear and anxiety in comparison to hens that use the range frequently (Campbell et al. 2016, 2019a; Hartcher et al. 2016; Larsen et al. 2018). Chronic fear and anxiety are negative welfare states but, these non-ranging hens have not been found to have higher stress responses as measured by baseline glucocorticoids and acute corticosterone responses (Campbell et al. 2016, 2017b; Hartcher et al. 2016; Larsen et al. 2018). There is some evidence that non-ranging hens have poorer plumage coverage, as has been shown in an experimental free-range system with hens assessed towards the end of the production cycle (Bari et al. 2020), but such relationships between range access and welfare indicators have not been found in other commercial flocks (Larsen et al. 2018). Further longitudinal studies tracking hens throughout the production cycle on commercial farms are needed to assess the long-term implications of ranging on hen welfare. Subsequent paragraphs discuss how range design can attract hens onto the range, but it is currently unknown whether sufficient attractants or enrichments would encourage every hen to range or whether a portion of the flock would always remain indoors by choice.

Interestingly, RFID studies have shown that free-range hens make short-lasting but frequent visits to the outdoor range throughout the day. For example, in a study on two commercial flocks (2000 Hy-Line Brown hens/flock), Larsen et al. (2017a) reported that most hens spent between 2 to 5 h on the range daily, spread across 10–20 daily visits. Most of the hens ventured farther than 10 m into the range, but hens spent about half of their ranging time in the wintergarden adjacent to the shed (also called ‘veranda’, comprised of an opaque overhead cover and littered floor), and, in general, hens spent most of their time close to the shed (Larsen et al. 2017a). Hence, hens used the range in a very dynamic fashion and changed range areas (i.e. veranda, close-range, far-range) approximately every 15 min (Larsen et al. 2017a). Similarly, Gebhardt-Henrich and colleagues (2014) studied 12 commercial flocks in Switzerland, with flock sizes from 2000 to 18 000 hens and reported individual range visits lasting between 10 and 102 min (average 42 min), of an available ranging time between 4 and 10 h daily (average 7 h). Tracking of small flocks of 50 Hy-Line Brown hens in an experimental free-range facility within Australia showed continuous movement in and out of the shed across the day, with the hens often following each other and acting as a cohesive group in their indoor–outdoor movement patterns (Campbell et al. 2018b); it is unclear whether the same movement patterns would be observed in commercial-scale flock sizes. No study has yet observed every hen being out on the range simultaneously, as there is always a proportion of the flock that remains indoors at any given time.

Multiple factors can influence whether a hen chooses to range or not, as reviewed by Pettersson and colleagues (2016). This review included all available international free-range studies, with no restriction on when the studies took place, although available research was almost exclusively conducted on brown layer strains. Factors that affected ranging included internal stocking density, flock size, pop-hole design, general shed design, range design and weather (Pettersson et al. 2016). Range design and resource availability have been shown to affect ranging on Australian commercial farms. Man-made range additions, including dust bathes, traffic cones, shelters and natural tree cover, all increased the number of hens found outdoors (de Koning et al. 2019a). Additionally, some man-made shelter features appear more attractive to laying hens than others. These are, in order of importance, visual density of the material used (90% UV block), horizontal orientation with one vertical side, and short horizontal structures over tall ones or tall vertical structures over short ones (Rault et al. 2013; Larsen et al. 2015). Shelterbelts, shade cloth and forage areas also increased the percentage of the flock that ranged, with forage being a particularly strong attractant, whereas shade cloth in isolation was not (Nagle and Glatz 2012). Weather can affect ranging, with strong winds, heavy rain and bright sunshine all reducing the number of hens observed on the range (de Koning et al. 2019a). However, comprehensive weather studies (e.g. as in the UK, Richards et al. 2011; Gilani et al. 2014), specifically on ranging in relation to the different types of (extreme) climates experienced on Australian farms (Singh et al. 2017), are lacking.

Once outside, where the hens go and how much of the available range area they utilise must be considered. Similar to factors that influence outdoor access or not, the design of the range and the resources offered have a strong impact on how much of the range area hens visit. Across commercial studies conducted both within Australia and internationally with varying flock sizes and brown strains, hens generally prefer to remain closer to the shed, with fewer hens venturing to or spending time in the outer areas of the available range (Rault et al. 2013; Chielo et al. 2016; Larsen et al. 2017a). This can result in high stocking density and environmental erosion close to the pop-holes, including higher build-up of soil nutrients, with unused land area further out into the range (D. L. M. Campbell, pers. obs.; Wiedemann et al. 2018). Man-made enrichments, shelter and vegetation all encourage hens out onto the range, as well as increasing the proportion of range area they utilise (Nagle and Glatz 2012; Rault et al. 2013; Pettersson et al. 2017). The variable range-design factors (such as e.g. slope, direction, and shape of the range, ground cover, overhead cover) can make it difficult to achieve consistent welfare outcomes and this partly explains the high variation in ranging patterns among farms. Vegetation, in particular, may be difficult to establish and maintain, depending on the climatic conditions and hen destruction of both foliage and soil (de Koning et al. 2019a). Identification of hardy plants that are resistant to hen damage and can prosper in poor conditions is needed, particularly for the development of range vegetation (de Koning et al. 2019b). Where foliage is not possible, man-made structures can still be beneficial and can often be constructed from materials already present on farm (de Koning et al. 2019a).

Range design can affect whether hens use the range or not, and it can also have an impact on what hens do when they are outdoors. Hen behaviour outdoors and any subsequent health and welfare impacts are critical for optimal management in free-range housing systems. The general view is that the outdoor environment provides greater opportunities for the expression of natural behaviour. While this may clearly be the case in comparison to cage systems, data are required to document behaviours performed on the range, and whether they differ quantitatively or qualitatively from the behaviours usually performed indoors. Including the comparison in behavioural frequencies between the outdoor and indoor section of a free-range system highlights the value of the range itself, depending on what indoor resources are provided (e.g. litter).

Behavioural studies of experimental and commercial flocks (150 Isa Brown and 2000 Hy-Line Brown hens respectively) have shown that hens are more likely to perform foraging while out on the range, and more resting indoors (Campbell et al. 2017b; Thuy Diep et al. 2018), but the ranges observed in these studies were devoid of trees or other shelter structures. Observations on several Australian commercial farms housing flocks from 3000 to 11 000 Hy-Line Brown hens have shown that hens mostly exhibited foraging and dust bathing within forested areas, and a great variety of behaviours within the shelters, such as foraging, dust bathing, resting, perching and preening (de Koning et al. 2019a). More hens dust-bathed and foraged in the sand pits that were provided for this purpose compared with other range areas (de Koning et al. 2019a). Finally, the behaviours of a flock of 8000 Hy-Line Brown hens in distinct areas of the outdoor range on an Australian commercial farm were documented to vary among locations according to the resources present, and varied according to the time of day, with the majority of behaviours observed to be foraging, preening, locomotion, resting and vigilance (Larsen et al. 2017b). More foraging and comfort behaviours were observed within the different tree and vegetation areas and more locomotion on the bare earth (Larsen et al. 2017b). A comparative study (Chielo et al. 2016) conducted across six commercial farms within the UK, housing flocks of Lohmann and Hy-Line Brown hens, mostly observed walking and foraging farther out on the range and, typically, standing in the area close to the shed. These UK farms were equipped with ‘activity kits’ that included shelter, dust baths and perches, in addition to some sapling trees (Chielo et al. 2016). Preening and dust bathing were observed infrequently outdoors (Chielo et al. 2016). Thus, the outdoor area is used for a wide range of behaviours, with foraging being preferentially performed in areas that encourage it, such as where grass and other vegetation is located. The extent to which these behaviours are specifically performed on the range may depend on whether foraging opportunities are also available indoors (e.g. litter versus slats). Further study across a selection of different free-range systems would allow assessment of range use depending on the outdoor and indoor conditions provided. Nevertheless, having an indoor and outdoor area does, in general, substantially increase the potential available space per hen to perform any behaviour.

The range area is a resource that provides extra space for hens to perform various behaviours and can be affected by range design. Thus, when considering attracting hens outdoors via modifications to the range design and/or provision of enrichments, the implications for bird welfare must also be assessed. Nagle and Glatz (2012) found no differences in feather coverage or bodyweight with the addition of shelter in experimental settings, but, in a commercial trial, the hens that had access to sorghum forage did have improved feather coverage. It must be highlighted that forage would need to be provided in a cautious manner as over-consumption of pasture can result in impaction and, ultimately, death of the hens (Ruhnke et al. 2015; Singh et al. 2017). A comprehensive assessment across 14 commercial farms within the UK that were provided a resource package on the range (pecking pans, shelters and wind chimes as a potential new pecking enrichment) found that, in comparison to the first year with no resource package, the provision of these resources improved distribution on the range and reduced feather-pecking behaviour in subsequent flocks (Pettersson et al. 2017). Although feather-pecking is multi-factorial in its aetiology and challenging to eliminate, alternative pecking opportunities have been shown to reduce its developments and prevalence (Rodenburg et al. 2013). Loose-housed hens, in general, 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. Thus, encouraging hens onto the range area and providing additional pecking stimulation to prevent the occurrence of feather damage is critical. More hens on the range also lowers the stocking densities inside where feather pecking frequency can be positively correlated with stocking density (Nicol et al. 1999). This type of bespoke management modification would be valuable to test across more commercial farms both within Australia and internationally, so as to document any associated welfare benefits.

There is individual variation in the utilisation of the range area. There are also important elements of range design that influence the types and frequencies of hen behaviour. Generally, foraging and walking occur more often while ranging. However, the health impacts of ranging must also be considered. These impacts can be measured by matching ranging behaviour with health variables at the individual level, or by overall flock assessments, for which the latter does not differentiate between ranging and non-ranging hens. In an Australian experimental setting using ISA Brown hens, frequent range use kept toe-nail length shorter, but there was no clear relationship between ranging and bodyweight (Campbell et al. 2017b), and most hens were still in visibly good condition up to 36 weeks of age. A further study in the same setting using Hy-Line Brown hens found shorter toe-nails, fewer comb wounds, and lower body fat and muscle weight, and heavier gizzard weights in those hens that spent the most time outdoors compared with hens that remained indoors when assessed at 65 weeks of age (Bari et al. 2020). Shorter toe-nail length was also found in free-range Lohmann Brown hens in an experimental system in Turkey, although individual range use was not measured (Yilmaz Dikmen et al. 2016). Hens that differed in the type of visit they made to the range, namely, long or short and frequent visits, varied in their gut health and digestibility of nutrients, indicating that ranging patterns in hens that regularly go outdoors can have differing metabolic impacts (Singh et al. 2016). Greater ranging may reduce feather pecking and improve plumage condition, as has been confirmed by greater plumage coverage in hens that spent the most time outdoors in small experimental free-range flocks (Bari et al. 2020). Across commercial farm studies with Hy-Line and Lohmann Brown hens in the UK, hens that were observed using the farthest areas of the range had better plumage condition (Chielo et al. 2016). This observation is supported by data from ISA Brown hens across the production cycle within commercial free-range farms in Spain where hens that used the outdoor range the most also had lower plumage damage (Rodriguez-Aurrekoetxea and Estevez 2016). Additionally, these hens showed lower frequencies of footpad dermatitis (Rodriguez-Aurrekoetxea and Estevez 2016), which was similar to reduced footpad hyperkeratosis in aviary hens with access to a range area across multiple commercial flocks in Belgium (Heerkens et al. 2016). On a flock level, research across 62 free-range and organic farms in the UK with Columbian Blacktail hens found that the risk of feather-pecking reduced with an increased range usage, as assessed by periodic visual flock-level counts of ranging hens (Lambton et al. 2010). However, Larsen and colleagues (2018) found no relationship between ranging and plumage damage within two commercial Hy-Line flocks in Australia. Similarly, no relationship between individual range use and plumage condition was found in a small experimental flock of ISA Brown hens in Australia (Hartcher et al. 2016). Larsen and colleagues (2018) sampled commercial hens and found few relationships between the frequency of outdoor access and physical health, showing no association with comb colour, beak condition, footpad condition or keel-bone condition, although hens that travelled farther in the range area had darker comb colour and better beak condition. de Koning et al. (2019a) did find better plumage on hens scored on the range than on hens that were scored within the shed, although the ranging behaviour of these hens was not specifically tracked.

A survey conducted by Singh et al. (2017) across 41 free-range farms, mostly of small to medium-sized flocks (<1000, 1000–3000, >3000 hens/flock) throughout Australia reported up to 10% mortality of hens by 40% of farmer respondents. Causes of mortality were reported to be predation (34%), cannibalism (29%), grass impaction (19.5%), heat stress (24%) and disease outbreaks (10%). The main diseases were reported to be fowl cholera (17%), coccidiosis (7.3%), spotty liver disease (7.3%) and infectious laryngotracheitis (4.8%). Additional causes of mortality were reported to be cold night-time temperatures, smothering, vent prolapse and injury. Thirty-two per cent of respondents reported that their hens had both internal and external parasites, but not all farmers checked for these and it was not reported whether the hens with parasites had additional health problems that could have increased susceptibility to parasite infections. This study was based on producer self-reports rather than specific diagnoses, but indicates the wide range of conditions and diseases that farmers think free-range hens may be susceptible to. However, risk of disease is increased by loose housing overall, and not limited to free-range systems only. For example, spotty liver disease is known to be prevalent within Australia, with higher occurrence in those hens with access to litter or ground soil such as in barn and free-range systems (Courtice et al. 2018). Internal parasites such as the helminth Ascardia galli are also more common in free-range hens within Australia (Dao et al. 2019) than in hens housed in cage systems. Ranging (rather than caged) hens might be susceptible to internal parasite infections, such as those caused by A. galli, because these parasites are within the soil (Permin et al. 1999) and the range can be contaminated by previous infected flocks (Höglund and Jansson 2011). However, loose-housed hens can be equally susceptible (Jansson et al. 2010) and a higher-range use may actually reduce infection level (Sherwin et al. 2013; Thapa et al. 2015), potentially resulting from the outdoor hens excreting more in the range, thus lowering the indoor density of faeces and chances of reinfection (Sherwin et al. 2013). In an experimental system, no differences in A. galli adult worm burden were found between hens that ranged frequently and those that stayed inside (Bari et al. 2020).

Comprehensive, comparative studies of free-range hen health and hen health from other types of housing systems have not yet been conducted within Australia. Comparisons among caged, enriched cage, and free-range research flocks of Lohmann Brown laying hens in Turkey found the highest mortality and more body wounds in the enriched-cage system, but more footpad dermatitis in the free-range system (Yilmaz Dikmen et al. 2016). Free-range hens had better plumage, and the highest tibial breaking strength, suggesting better leg health, and caged hens had the highest heterophil : lymphocyte ratio (a measure of blood cell-type concentrations to infer stress, Davis et al. 2008). Measures of tonic immobility (fear) and other bone and blood parameters were similar across the systems. Free-range hens have improved bone strength in comparison to caged hens (Shipov et al. 2010) but, ultimately, bone parameters are likely to also be strongly influenced by the types of housing available indoors within free-range systems. Kolakshyapati et al. (2019) found no differences in tibial bone parameters between high- and low-ranging hens in a commercial flock housed within an aviary-free-range system. Indoor perches or aviaries may further increase the ability to exercise but may also increase opportunities for collision or pressure damage (Wilkins et al. 2011). Another comparative study from commercial farms in the UK, with mostly Hy-Line and Lohmann strains, showed that free-range hens had better plumage than did hens from barn, furnished cage and conventional cage systems (Sherwin et al. 2010). However, free-range hens had the most vent pecking and numbers of keel-bone fractures similar to those for hens housed in barns but greater than those for hens housed in conventional or furnished cages (Sherwin et al. 2010). Finally, a meta-analysis of 10 studies from the UK and Europe on layer mortality across multiple strains found the highest model-predicted mortality in free-range systems (Weeks et al. 2016). Causes of mortality in free-range systems have been listed as smothering, parasites, disease from wild birds and predation (Elson 2015). However, a detailed study on the physical health of individual commercial free-range laying hens at the end of lay, as compared with other types of housing systems within Australia, is warranted. Further assessment of bird health at the individual level and in relation to their ranging pattern would be informative at an international scale where sampling of commercial flocks (housing thousands of individuals) may increase the chances of seeing associations between ranging and illnesses, infections and injuries that are more prevalent in larger group sizes. Detailed assessment of the causes of poor health and/or mortality may enable management modification to reduce the risks. Optimal management of free-range systems depends on the housing design and climatic conditions. Ultimately, the selection of laying hen strains specifically suited to free-range housing systems in Australian climates may be necessary.

Data on the influences of specific indoor-shed designs and different management practices on range access within Australia are lacking, but international research points to the importance of these factors. Flock size is negatively correlated with range use and can affect how many hens use the range, the time spent on the range, and hen behaviour, with more ranging and foraging occurring in smaller flock sizes (Gebhardt-Henrich et al. 2014; Gilani et al. 2014; Bestman et al. 2019). Both higher indoor stocking density (Gilani et al. 2014) and higher outdoor stocking density (Campbell et al. 2017a) can also reduce ranging. Higher internal light intensity or internal daylight also increased the percentages of hens outdoors across multiple flocks within the UK and Europe (Gilani et al. 2014; Bestman et al. 2019). Greater availability of pop-holes increased range access (Gilani et al. 2014), with Pettersson and colleagues (2018) demonstrating that when pop-holes were available only on one side of the shed, hens that preferred to roost farther away from the pop-holes were less likely to be observed on the range. In a commercial free-range-aviary system in Australia, a positive association was found between range use and the use of the lower indoor aviary tier (Sibanda et al. 2020). Some farms also use mobile sheds where the indoor housing facilities can be moved to different parts of a pasture regularly, rather than being in a fixed position (Singh et al. 2017). However, the effects of using mobile sheds on hen ranging behaviour have not been extensively scientifically studied, and, thus, data from these systems are lacking.

Housing-system designs among free-range farms within Australia can vary extensively (Singh et al. 2017; de Koning et al. 2019a) as well as management practices such as the age of first opening the pop-holes, whether a training program is used to encourage the hens to access the range, and for how long the pop-holes are open each day. Weather can change the topography of the range such as the availability of dry dust bathing areas (de Koning et al. 2019a). Weather can also affect litter or other environmental conditions inside the shed. All these different variables can make management of a specific system challenging for the farmer and for the hens. Hens exhibit a high physiological stress response as well as behavioural indicators of frustration when locked indoors after previously being accustomed to daily range access (Campbell et al. 2018a; D. L. M. Campbell, pers. comm.), and restricted range access may increase the occurrence of feather pecking (Bestman et al. 2017). Stress can likely increase susceptibility to disease outbreaks such as spotty liver disease, but conversely some outdoor conditions such as dirty drinking water on the range may also increase outbreak risk of this disease (Scott 2016; Courtice et al. 2018), thus necessitating locking the hens inside the shed. Subsequently, free-range hens may need to be more adaptable to a variety of different conditions and changing environments to thrive in these systems. The rearing period may offer an opportunity of better preparing free-range hens for the challenges of the adult housing system. Rearing conditions are critical for optimal behavioural and physical development of hens (Campbell et al. 2019b) and matching the rearing system with the layer system is recommended (Janczak and Riber 2015). Across commercial systems within the UK, there was no difference in ranging between flocks provided outdoor access during rearing (at 8 weeks or 16 weeks of age), or as adults (Gilani et al. 2014). However, another study reported more hens out as adults for organic free-range flocks in Europe if they were reared with outdoor access (Bestman et al. 2019). In an experimental trial conducted with Hy-Line Brown hens in Australia, variable and changing enrichments provided in the first 3 weeks of life resulted in lower stress responses to imposed environmental stressors when the hens were ~40 weeks of age (Campbell et al. 2018a). A further experimental trial with Hy-Line Brown hens found that perching structures provided during the 16 weeks of rearing increased range use in comparison to pullets reared with no perches or pullets given variable novel objects for 16 weeks (Campbell et al. 2020). The hens reared with no additional materials also showed more plumage damage than did the enriched-reared hens at the end of the lay cycle (Bari et al. 2020). When pullets destined for ranging are reared indoors, enrichments during the development period may be a method for optimising their welfare and adaptability as ranging adults.

Radio-frequency identification systems have demonstrated that the majority of hens range, but their indoor–outdoor movement across the day is highly dynamic. The extent to which hens range and how far they go are affected by the design of the range, and natural or man-made shelter and outdoor additions can increase range use and range distribution. Standardising range designs on the basis of hen requirements among different farms is challenging, and it is likely to be related to the surrounding climatic conditions, which remains poorly understood, specifically under Australian conditions. The provision of an outdoor area does provide more space for hens and the ability to perform natural behaviour such as walking and foraging. Foraging is observed more frequently outdoors than indoors, but the behavioural repertoire depends on the range design such as the presence of shelter, vegetation or enrichment. The impact of different types of indoor-shed designs on the behaviours performed outdoors is not known (e.g. slatted floors versus litter). Encouraging more foraging outdoors could reduce the prevalence of feather pecking, but this needs to be further validated on commercial farms. The benefits of outdoor access can be measured at a flock level or on an individual hen basis by matching welfare measures with their specific ranging patterns. Ranging can improve plumage cover and may reduce footpad dermatitis, but not all studies have found clear relationships between health and, specifically, use of the range; further validation in commercial settings is required. The few hens that use the range infrequently or not at all show higher fear and anxiety, but whether ranging is associated with positive affective states remains to be investigated. Free-range hens are potentially exposed to greater risks such as disease, heat stress, predation and parasites but their afflictions relative to other loose-housed or caged systems within Australia are poorly documented. Comparisons of individual-hen health relative to range access across commercial flocks is warranted to better determine management practices that optimise free-range hen health and welfare. Optimal management of hen welfare within free-range systems can be challenging. The environment is more difficult to control, being dependent on conditions such as weather and range vegetation cover, and management practices can vary among farms, such as age of first range access and daily access dependent on prevailing weather. More research is required to assess the impacts of indoor-shed design and best management practices. Conditions offered during pullet rearing may be an avenue to better prepare hens for optimal outdoor access as adults.

Australian Eggs provided funding support for the review, but had no role in the content.