Systems For Laying Hens Research Articles

Space use of free-range laying hens on two outdoor ranges with different amounts of vegetation cover

Consumers’ awareness of animal welfare in farm animal husbandry – including laying hen systems – increased in the last few decades. As a result, more and more farmers in Austria changed from barn systems to free-range husbandry. However, lack of structure and protective cover in the outdoor area might cause poor use of major parts of the outdoor range. Since the ancestor of domestic chicken – the red junglefowl – inhabits dense jungle forests with manifold ground vegetation, the structural design of an outdoor area might be of high importance for laying hens. To examine this assumption, a 15×15 m grid of barrier tape was brought out on the ground of the outdoor ranges of two commercial free-range laying hen farms that differed in the amount of vegetation cover they provided. Using action cams, we took pictures of each quadrant in ten-minute intervals from 09:00 h to 21:00 h for a total of three full days. We ran GAMs for each farm separately with number of hens per quadrant and interval as dependent variable, and vegetation cover (yes/no) and position (edge/centre) of the quadrant, distance to the shed (in m), as well as temperature (in °C) as predictors. Date, time, and quadrant ID were included as smooth terms. We found a more even and widespread use of space of hens on the outdoor range with a large amount of vegetation cover (farm 1) compared to the range with a small amount of vegetation cover (farm 2). However, the number of hens decreased with increasing distance to the shed on both farms. Hens preferred edge over centre quadrants on the range of farm 1, but preferred centred quadrants with vegetation cover over those without cover on the range of farm 2. On the ranges of both farms, the number of hens decreased with increasing temperature on quadrants without vegetation cover, whereas no such effect was found for covered quadrants. These findings suggest vegetation cover to be a key factor for extensive range use, particularly in view of the expected increase in temperature due to climate change. Therefore, we recommend farmers to provide hens with highly structured outdoor ranges, not only to improve range use but also to offer hens a more species-appropriate environment, which is assumed to increase the hens’ welfare as well.

Estimating production costs and retail prices in different poultry housing systems: conventional, enriched cage, aviary, and barn in Japan

For many producers, introduction of improved animal welfare systems is a turning point in their future production strategies as it increases production costs. The increase in egg retail prices is of growing concern not only for producers, but also for retailers and consumers. However, no report has calculated the estimated production costs or retail prices associated with introducing practices that support improved animal welfare in poultry farms in Japan. Therefore, this study aimed to estimate the production costs and table egg prices of 6 types of laying hen systems: conventional cage (CC): 8- and 12-tiers (CC8, CC12), enriched cage (EC): 8- and 12-tiers (EC8, EC12), aviary (AV), and barn systems (BR). Production costs include land purchases, construction costs of facilities, equipment and machinery, quantity of feed provided, farming materials invested, and wages.As a result, farm gate prices were estimated as CC8 = 12.19, CC12 = 12.19, EC8 = 14.52, EC12 = 14.52, AV = 21.14, and BR = 28.74 [yen/egg], and the production cost, including building the new farm, increased by EC8 = 19.1%, EC12 = 19.1%, AV = 73.4%, and BR = 135.7%, respectively, referring to the value of CC. The results show that the prices increase in systems between CC and BN. The retail price or table egg price was estimated to be CC8 = 24.68, CC12 = 24.68, EC8 = 28.07, EC12 = 28.07, AV = 37.27, and BR = 48.53 [yen/egg]. The retail price of BR is approximately twice that of CC. In addition, assuming that all of Japan's eggs were produced in the BR system, the soaring cost of eggs would likely affect the prices of factory eggs, such as liquid eggs and other products, thus affecting the prices of various food products.Understanding the significant management costs that affect the retail price of eggs would facilitate improved policies and practical approaches to support poultry farms and sustainable farming activities while addressing public concerns.

The Potential of Understory Production Systems to Improve Laying Hen Welfare.

Simple SummaryNon-cage farming is gradually becoming the mainstream mode of poultry farming worldwide, which has led to concerns regarding the welfare of laying hens in China. Under huge pressure for the supply of eggs, China, with relatively insufficient land resources, is highly dependent on cage systems, thus posing significant challenges related to animal welfare. In the context of this dilemma, China’s abundant woodland resources provide a means to improve the welfare of laying hens, in particular, providing a wide living space for laying hens to express their natural behaviours, such as foraging and reproduction. At the same time, this profitable farming model has been welcomed and supported by farmers in some areas of China, and is gradually being promoted, which may provide a template and confidence for China and other countries to address the challenges of keeping hens in non-cage systems in order to improve animal welfare.The welfare of laying hens in cage systems is of increasing concern. Represented by the European Union’s ‘End the Cage Age’ initiative, more and more countries have advocated cage-free farming. China, an important country for poultry farming and consumption in the world, is highly dependent on cage systems and lacks confidence in alternative (e.g., free-range) systems. In this context, using China’s abundant woodland resources (including natural forests, plantations, and commercial forests) to facilitate the management of laying hens in a free-range environment may provide highly promising welfare improvement programs. On the basis of the Five Freedoms, we assess the welfare status of understory laying hen management systems with reference to the behavioural needs and preferences of laying hens and the EU standards for free-range and organic production (highest animal welfare standards in the world). The results show that the considered systems meet or even exceed these standards, in terms of key indicators such as outdoor and indoor stocking density, outdoor activity time, and food and drug use. Specifically, the systems provide sufficient organic food for laying hens without using antibiotics. They allow laying hens to avoid beak trimming, as well as to express nesting, foraging, perching, reproductive, dustbathing and other priority behaviours. The presence of roosters and higher use of woodland space allow the laying hens to achieve better feather and bone conditions, thus reducing stress and fear damage. Notably, the predation problem is not yet considered significant. Second, there is evidence that understory laying hen systems are profitable and have been welcomed and supported by farmers and governments in the southwest, south, and north of China. However, whether it can be scaled up is uncertain, and further research is needed. In addition, laying hens in this management system face various risks, such as foot injury, parasitism, and high dependence on consumer markets, which must be considered. Overall, agro-forestry, or accurately, understory poultry raising, provides opportunities and possibilities for free-range laying hens and welfare improvement in China and other countries.

Examining the catching, carrying, and crating process during depopulation of end-of-lay hens

Summary Laying hen flocks undergo depopulation at end of lay, a difficult process that has been associated with injuries and is considered stressful to hens and human collectors. To date, most assessments of depopulations have been conducted within cage housing systems, layers, or noncage broilers, thus offering little relevance to noncage laying hen systems including aviaries. Given that the predominant housing systems in Switzerland are multitier aviaries and their growing popularity in general, our study was undertaken to establish a baseline for hen injuries and stress as well as the experience of human workers during depopulation. For the effort, a total of 15 individual farms were visited, and a battery of assessments was made on a total of 603 individual end-of-lay hens. In addition, potentially influential factors such as time of day, handling duration, or time into depopulation were recorded and analyzed. The results suggest that approximately 8.1% of hens sustain severe injuries (i.e., fractures and muscle damage) or exhibit a considerable stress reaction (i.e., increased corticosterone levels), whereas 90% of laying hens are only mildly affected.

Effect of Production Systems for Laying Hens on Hen Welfare

This review article discussed the effects of various production systems on the welfare of laying hens. The global egg production capacity has been increasing with the evolving production systems which are driven by the consumer preferences. In developed countries, the egg industry has shifted from focusing on quantity and quality of eggs to asking questions of how these eggs are produced. Animal welfare issues emphasized by consumers in these countries led to the banning of conventional cages as seen by European Union in 2012. Such legal measures have uplifted research in various alternative production systems which are thought to be animal friendly. Countries that have adjusted to alternative systems such as free range are registering an increase in the number of free range eggs which is a positive sign for an industry that is willing to adapt and move forward. However, in developing countries, conventional cages are still being used because they are fundamental to the quantity of egg production which is a success indicator of the egg industry. In addition, lack of awareness within the consumers and local producers that birds are sentient has not helped the poultry industry in such countries. However, the alternative production systems have also not fulfilled all the behavioural needs of the animals and, hen welfare issues such as keel and bone damage are common in enriched and perched systems. Also, the high prevalence of diseases and parasites are observed with significant levels in litter floor and outdoor systems an issue attributable to the direct contact between birds and soil or faces. Due to the continuing welfare issues in all laying hen production systems, it is suggested that in addition to genetic selection for traits like bone strength, reduced feather pecking, research should combine both the modification of equipment‘s or materials used in each production system and environmental factors such as illumination and temperature as an alternative to improve hen welfare.

Laying hen strains and breeding system: A review of hen behavior and welfare, hen production performance and eggs quality traits in Africa and around the world

The breeding system for laying hens has been the focus of scientific research for many years. During the last decade, new laying hen systems were rapidly introduced with the aim of improving the health of poultry and the welfare of consumers, producers and industries on the one hand and meeting the requirements on the other hand. The choice of the genetic type usually depends on the production performance and the color of the eggs. To this end, the aim of this work was to make a comparative review of the results obtained by different authors on effect of strain and farming system on production performance (egg production and mortality) and the characteristics of egg quality (egg weight, proportion of different parts of the egg, Haugh units, egg yolk color and carotenoid) of laying hens. Although the productive performance in ground systems is often low compared to the cage farming system, the eggs of the ground-based system have been proven by many studies to have the best nutritional properties. This review of literature on the use of different strains and different table egg farming systems could give a new direction to research.

Influence of different housing systems on prevalence of keel bone lesions in laying hens

ABSTRACTThe present study aimed to investigate the effect of three housing systems (furnished cages – FC, barns – B, and free-range – FR) on the prevalence and severity of keel bone protrusion and deformations. These health and welfare indicators were measured at the slaughterhouse, using a 4-point scale (0 = absence, 1 = slight, 2 = moderate and 3 = severe). Keel bone deformation was also categorized in relation to the presence of compression over the ventral surface, deviation from a 2D straight plane and deviation from the transverse (C-shaped) or median sagittal (S-shaped) plane. The housing system had a significant effect on prevalence of keel bone deformation (χ2 = 45.465, df = 6, P < 0.001). In FR systems 60.4% of hens presented keel bone deformation, followed by 54.2% in FC and 53.5% in B; however, higher scores for keel bone deformations were more frequent in B systems. Although keel bone protrusion was observed in all laying hen systems, the majority of hens only presented a slight degree (score 1) of protrusion. A positive correlation was obtained for keel bone protrusion and emaciation. The results could be used to initiate detailed investigations into problematic issues that occur during the laying period to improve the health and welfare conditions on farms.

Using Radio-Frequency Identification Technology to Measure Synchronised Ranging of Free-Range Laying Hens.

Simple SummaryFree-range laying hens can choose to be indoors or outdoors. Individual hens vary in their ranging choice and this behaviour could also be affected by their flock mates. Radio-frequency identification tracking of individual hens in experimental free-range pens with group sizes of 46–50 hens was used to study flock ranging patterns. Across the day, hens moved through the range pop-holes in the same direction as other hens above levels expected by random chance, termed ‘pop-hole-following’. Hens were also simultaneously indoors or outdoors with other specific hens more often than expected by random chance, termed ‘hen-pair association’. Chicks that were provided variable stimulatory and structural enrichments from 4 to 21 days showed higher pop-hole-following and hen-pair association than non-enriched birds. The individual birds within these small hen groups were behaving primarily as a cohesive flock which has implications for understanding the group-level behaviour of hens. Further research would analyse if similar social movement patterns were present in larger commercial free-range flocks and how early rearing environments may affect adult social behaviour.Free-range laying hen systems provide individuals a choice between indoor and outdoor areas where range use may be socially influenced. This study used radio-frequency identification technology to track the ranging of individually-tagged hens housed in six experimental free-range pens from 28 to 38 weeks of age (46–50 hens/pen). All daily visits to the range were used to study group behaviour. Results showed that 67.6% (SD = 5.0%) of all hen movements through the pop-holes outdoors or indoors were following the movement of another hen (‘pop-hole-following’) compared to only 50.5% of movements in simulated random data. The percentage overlap in time that all combinations of hen pairs within each pen spent simultaneously outdoors or indoors showed a median value of overlap greater than the 90th percentile of random data. Pens housing hens that had been provided variable enrichments from 4 to 21 days (n = 3 pens) showed higher ‘pop-hole-following’ behaviour and a higher percentage of hen-pair association compared to hens reared in non-enriched conditions (n = 3 pens). These results show that birds in each free-range pen were primarily a cohesive flock and early enrichment improved this social cohesiveness. These results have implications for understanding free-range flock-level behaviour.

Mite fauna (Acari) associated with the poultry industry in different laying hen management systems in Southern Brazil: a species key

This study is based on results from a large project on the mite diversity in commercial laying hen systems in Brazil. It aims to identify potential biocontrol agents amongst mites present in poultry farms, with a focus on one feather mite pest Megninia ginglymura. A secondary goal is to provide an operational identification tool to help the development of biological control in poultry farms. Sampling was conducted from August 2013 to August 2014, with 43 sampling events, in three different laying hen management systems. We used traps, laying hen feathers, and abandoned wild bird nests to collect the mites. A total of 38,862 mites belonging to 23 families and 39 species were found, including 17 species exclusively found in traps, six in wild bird nests, and one in feathers. The most abundant and frequent ectoparasitic species was M. ginglymura (76.3%; observed in all management systems). Amongst other mites, Tydeidae showed the highest richness with five species (Brachytydeus argentinensis (Baker, 1970), Brachytydeus australensis (Baker, 1970), Brachytydeus obnoxia (Kuznetzov and Zapletina, 1972), Brachytydeus oregonensis (Baker, 1970), and Brachytydeus tuttlei (Baker, 1965)), followed by Cheyletidae with four species (Chelacheles bipanus Summers and Price, 1970, Cheyletus eruditus (Schrank, 1781), Cheyletus malaccensis (Oudemans, 1903), and Cheletomimus (Hemicheyletia) wellsi (Baker, 1949)). Potential predatory species for biological control were C. malaccensis (9.4%), Typhlodromus transvaalensis (Nesbitt, 1951) (0.8%), Blattisocius keegani (Fox, 1947) (0.7%), and Blattisocius dentriticus (Berlese, 1918) (0.4%). A dichotomous key is provided to identify 48 species dwelling in Brazilian layer farms.

Early enrichment in free-range laying hens: effects on ranging behaviour, welfare and response to stressors

Free-range laying hen systems are increasing within Australia. The pullets for these systems are typically reared indoors before being provided first range access around 21 to 26 weeks of age. Thus, the rearing and laying environments are disparate and hens may not adapt well to free-range housing. In this study, we reared 290 Hy-Line® Brown day-old chicks divided into two rooms each with feed, water and litter. In the enriched room, multiple structural, manipulable, visual and auditory stimuli were also provided from 4 to 21 days, the non-enriched room had no additional objects or stimuli. Pullets were transferred to the laying facility at 12 weeks of age and divided into six pens (three enriched-reared, three non-enriched-reared) with identical indoor resources and outdoor range area. All birds were first provided range access at 21 weeks of age. Video observations of natural disturbance behaviours on the range at 22 to 23 and 33 to 34 weeks of age showed no differences in frequency of disturbance occurrences between treatment groups (P=0.09) but a decrease in disturbance occurrences over time (P<0.0001). Radio-frequency identification tracking of individually tagged birds from 21 to 37 weeks of age showed enriched birds on average, spent less time on the range each day (P<0.04) but with a higher number of range visits than non-enriched birds from 21 to 24 weeks of age (P=0.01). Enriched birds accessed the range on more days (P=0.03) but over time, most birds in both treatment groups accessed the range daily. Basic external health scoring showed minimal differences between treatment groups with most birds in visibly good condition. At 38 weeks of age all birds were locked inside for 2 days and from 40 to 42 weeks of age the outdoor range was reduced to 20% of its original size to simulate stressful events. The eggs from non-enriched birds had higher corticosterone concentrations following lock-in and 2 weeks following range reduction compared with the concentrations within eggs from enriched birds (P<0.0001). Correspondingly, the enriched hens showing a greater increase in the number of visits following range area reduction compared to non-enriched hens (P=0.02). Only one rearing room per treatment was used but these preliminary data indicate 3 weeks of early enrichment had some long-term effects on hen ranging behaviour and enhanced hen’s adaptability to environmental stressors.

Ectoparasitism of commercial laying hen by Megninia ginglymura (Mégnin) (Acari): population dynamic and distribution on the body regions

Ectoparasites are temporary or permanent skin dwellers. Megninia ginglymura (Mégnin) (Analgidae) causes economic damage in commercial poultry farms as a result of lower egg production or even death of the host. Little is known about Megninia ginglymura's life cycle and infestation. This study aimed to evaluate the preference of M. ginglymura for different body regions of the host Gallus gallus L. and its abundance and population dynamics in different laying hen houses. Samples were collected from August 2013 to August 2014 in three different commercial laying hen systems: automatic production systems (A1,2,3); semiautomatic systems (S1 (free of pesticides) and S2) and free-range system (FR). Ten laying hen were sampled each laying hen house and it were collected feathers were collected from different body regions form 10 hens in each laying house. A total of 28,305 specimens belonging to M. ginglymura were collected. Higher abundance was noted in S1 (9,234), S2 (9,121), and FR (5,873) and lower in A2 (2,211), A3 (1,628), and A1 (238). The dorsum (back of the body) region showed the highest abundance, mean abundance, and prevalence, representing 29.5% of the total specimens collected. The cloacal region was the second with 21.1% of the total of this ectoparasite. The abdomen and neck represented 20.8% and 19.6%, respectively. The inner wings presented the lowest abundance, mean abundance, and prevalence in all laying hen houses (9.0% of specimens). The prevalence was significantly different in automatic, semiautomatic, and free-range systems. The population peaks seems to coincide with periods of high temperatures and precipitation. Populations of this species already exhibit resistance to synthetic chemical pesticide.

Susceptibility to keel bone fractures in laying hens and the role of genetic variation

Keel bone fractures are a well-known welfare problem in modern commercial laying hen systems. The present study sought to identify genetic variation in relation to keel bone fracture susceptibility of 4 distinct crossbred and one pure line, and by extension, possible breeding traits. Susceptibility to fractures were assessed using an ex vivo impact testing protocol in combination with a study design that minimized environmental variation to focus on genetic differences. The 5 crossbred/pure lines differed in their susceptibility to keel bone fractures with the greatest likelihood of fracture in one of the 3 commercial lines and the lowest susceptibility to fractures in one of the experimental lines. Egg production at the hen-level did not differ between the crossbred/pure lines (P >0.05), though an increased susceptibility to keel bone fractures was associated with thinner eggshells and reduced egg breaking strength, a pattern consistent among all tested crossbred/pure lines. Our findings suggest an association between egg quality and bone strength which appeared to be independent of crossbred/pure line. The findings indicate the benefit of the impact methodology to identify potential breeding characteristics to reduce incidence of keel fracture as well as the potential relationship with eggshell quality.

Egg production and egg quality in free-range laying hens housed at different outdoor stocking densities

Free-range laying hen systems are increasing in number within Australia. Variation in outdoor stocking densities has led to development of a national information standard on free-range egg labeling, including setting a maximum density of 10,000 hens per hectare. However, there are few data on the impacts of differing outdoor densities on production and egg quality. ISA Brown hens in small (150 hens) flocks were housed in identical indoor pens, each with access (from 21 weeks) to different sized ranges simulating one of three outdoor stocking densities (2 replicates each: 2,000 hens/hectare (ha), 10,000 hens/ha, 20,000 hens/ha). Hen-day production was tracked from 21 through 35 weeks with eggs visually graded daily for external deformities. All eggs laid on one day were weighed each week. Eggs were collected from each pen at 25, 30, and 36 weeks and analyzed for egg quality. There were no effects of outdoor stocking density on average hen-day percentage production (P = 0.67), egg weight (P = 0.09), percentages of deformed eggs (P = 0.30), shell reflectivity (P = 0.74), shell breaking strength (P = 0.07), shell deformation (P = 0.83), or shell thickness (P = 0.24). Eggs from hens in the highest density had the highest percentage shell weight (P = 0.004) and eggs from the lowest density had the highest yolk color score (P < 0.001). The amount of cuticle present did not differ between densities (P = 0.95) but some aspects of shell colors (P ≤ 0.01) and location of protoporphyrin IX (P = 0.046) varied. Hen age affected the majority of measurements. Stocking density differences may be related to hen diet as previous radio-frequency identification tracking of individual hens in these flocks showed birds used the range for longer in the lowest density and the least in the highest density, including depleting the range of vegetation sooner in the smaller ranges. An additional study assessing the relationship between individual hen range use, nutrition, and egg quality is warranted.

Outdoor stocking density in free-range laying hens: effects on behaviour and welfare

Free-range laying hen systems are increasing within Australia and research is needed to determine optimal outdoor stocking densities. Six small (n=150 hens) experimental flocks of ISA Brown laying hens were housed with access to ranges simulating one of three outdoor stocking densities with two pen replicates per density: 2000 hens/ha, 10 000 hens/ha or 20 000 hens/ha. Birds were provided daily range access from 21 to 36 weeks of age and the range usage of 50% of hens was tracked using radio-frequency identification technology. Throughout the study, basic external health assessments following a modified version of the Welfare Quality® protocol showed most birds were in visibly good condition (although keel damage was increasingly present with age) with few differences between stocking densities. Toenail length at 36 weeks of age was negatively correlated with hours spent ranging for all pens of birds (all r⩾−0.23, P⩽0.04). At 23 weeks of age, there were no differences between outdoor stocking densities in albumen corticosterone concentrations (P=0.44). At 35 weeks of age, density effects were significant (P<0.001) where the eggs from hens in the highest outdoor stocking density showed the highest albumen corticosterone concentrations, although eggs from hens in the 10 000 hens/ha density showed the lowest concentrations (P<0.017). Behavioural observations of hens both on the range and indoors showed more dust bathing and foraging (scratching followed by ground-pecking) was performed outdoors, but more resting indoors (all P<0.001). Hens from the 2000 hens/ha densities showed the least foraging on the range but the most resting outdoors, with hens from the 20 000 hens/ha densities showing the least amount of resting outdoors (all P<0.017). Proportions of dust bathing outdoors tended to differ between the stocking densities (P=0.08). For each of the health and behavioural measures there were differences between pen replicates within stocking densities. These data show outdoor stocking density has some effects on hen welfare, and it appears that consideration of both individual and group-level behaviour is necessary when developing optimal stocking density guidelines and free-range system management practices.

Influence of laying hen systems on the mite fauna (Acari) community of commercial poultry farms in southern Brazil.

Intensive production of confined laying hens affects their welfare and increases the risk of epidemics. Ectoparasites as hematophagous and feather mites cause low productivity and decreased egg quality. This study aimed to determine the diversity of mites captured with traps in different commercial systems of laying hens (Gallus gallus L.) (Phasianidae) in Taquari Valley, Rio Grande do Sul, Brazil. Samplings were conducted from August 2013 to August 2014, totaling 21 sampling events in three different commercial laying hen systems: automatic production systems (A(1), (2), (3)), semiautomatic systems (S(1), (2)), and free-range system (FR). A total of 9981 mites belonging to 21 families, 31 genera, and 35 species were found. Acaridae, Caligonellidae, and Cheyletidae showed the highest richness with four species each. Megninia ginglymura (Mégnin, 1877) (Analgidae) was the most abundant ectoparasite species with 1328 specimens and was present in all commercial laying hen systems. No hematophagous mites were found. Cheyletus malaccensis(Cheyletidae) (3503), Typhlodromus transvaalensis (Phytoseiidae) (304), and Blattisocius keegani (Blattisocidae) (181) were the predators present in all systems. The similarity with control system (S(1)--without pesticide) was low (36.5 %) when compared to all other commercial laying hen systems, and it had the highest richness. In FR, low populations of mites and highest diversity were observed. The commercial laying hen system and the management influence the mite fauna in poultry farms.

The prevention and control of feather pecking: application to commercial systems

Studies on the prevalence of feather pecking in different commercial laying hen systems and its welfare and economic impacts are reviewed in the following paper. Current methods for controlling feather pecking include beak-trimming and alterations to light regimes, but these methods have significant disadvantages from the perspective of bird welfare. A substantial body of research has now identified risk factors for feather pecking during both the rearing and laying periods. It is argued that these findings can be translated into optimised management practices that can prevent and control feather pecking whilst simultaneously conferring welfare benefits. The genetic basis of feather pecking is considered, and studies that suggest group selection techniques could produce birds with a reduced tendency to feather peck in commercial flocks are highlighted.

Henne oder Manager - wer ist für Staub und Ammoniak im Stall verantwortlich?

According to EU and national regulations in Germany layers are kept not any longer in cages. There are alternatives on the market. An assessment of different keeping/management systems for laying hens with regard to individuals’ health and environmental protection is required. One open question concerned is the relevance of airborne dust and ammonia. This paper deals with investigations running in two systems for keeping laying hens – aviary and German small group housing system – regarding dust and ammonia concentrations inside the stable and their emission flows. The systems vary in size, stocking density and management. First data on airborne exposure indicate differences between the housing systems investigated. The ammonia concentrations reach from less than 1 ppm to more than 20 ppm and PM4 from 0,1 to 2 mg/m³. Ammonia produced essentially by the birds’ faeces. Manure management is one of the most important factors to reduce the concentration of ammonia. Dust emissions are mainly caused by birds’ activity which can be influenced by e.g. the light programme

Individual variation in hens' pre-laying behaviour and the incidence of floor eggs

Free-range laying hen systems are increasing within Australia and research is needed to determine optimal outdoor stocking densities. Six small (n=150 hens) experimental flocks of ISA Brown laying hens were housed with access to ranges simulating one of three outdoor stocking densities with two pen replicates per density: 2000 hens/ha, 10 000 hens/ha or 20 000 hens/ha. Birds were provided daily range access from 21 to 36 weeks of age and the range usage of 50% of hens was tracked using radio-frequency identification technology. Throughout the study, basic external health assessments following a modified version of the Welfare Quality® protocol showed most birds were in visibly good condition (although keel damage was increasingly present with age) with few differences between stocking densities. Toenail length at 36 weeks of age was negatively correlated with hours spent ranging for all pens of birds (all r⩾−0.23, P⩽0.04). At 23 weeks of age, there were no differences between outdoor stocking densities in albumen corticosterone concentrations (P=0.44). At 35 weeks of age, density effects were significant (P<0.001) where the eggs from hens in the highest outdoor stocking density showed the highest albumen corticosterone concentrations, although eggs from hens in the 10 000 hens/ha density showed the lowest concentrations (P<0.017). Behavioural observations of hens both on the range and indoors showed more dust bathing and foraging (scratching followed by ground-pecking) was performed outdoors, but more resting indoors (all P<0.001). Hens from the 2000 hens/ha densities showed the least foraging on the range but the most resting outdoors, with hens from the 20 000 hens/ha densities showing the least amount of resting outdoors (all P<0.017). Proportions of dust bathing outdoors tended to differ between the stocking densities (P=0.08). For each of the health and behavioural measures there were differences between pen replicates within stocking densities. These data show outdoor stocking density has some effects on hen welfare, and it appears that consideration of both individual and group-level behaviour is necessary when developing optimal stocking density guidelines and free-range system management practices.