Welfare Of Laying Hens Research Articles

Effect of Interrupting the Daily Scotophase Period on Laying Hen Performance, Bone Health, Behavior, and Welfare; Part I: Bone Health

Effect of Interrupting the Daily Scotophase Period on Laying Hen Performance, Bone Health, Behavior, and Welfare; Part I: Bone Health

Enhancement of laying hen welfare regulation in Serbia: a lesson to be learned from the EU experience to reduce the prevalence of keel bone damage

Enhancement of laying hen welfare regulation in Serbia: a lesson to be learned from the EU experience to reduce the prevalence of keel bone damage

Associations among computed tomographic measures of bone and muscle quality and biomechanical measures of tibiotarsal bone quality in laying hens.

The objectives of the current study were to quantify laying hen sternal carina (keel) and tibiotarsal bone and muscle quality using clinical CT, tissue level, and biomechanical measures; test associations among muscle transverse sectional area, bone mineral density, and biomechanical measures of bone quality; and determine whether CT measures of bone and muscle quality would be predictive of biomechanical measures of tibiotarsal bone quality. 60 40-week-old Hy-Line brown laying hens were used. Associations among CT imaging, tissue level, and biomechanical measures of tibiotarsal and keel bone and muscle quality were tested using multivariate correlational analyses. Bivariate and generalized regressions were performed to determine whether CT measures were predictive of biomechanical measures of tibiotarsal bone quality. Low positive correlations were identified between tibiotarsal muscle transverse-sectional area (cross-sectional area [CSA]) and bone mineral density (BMD) in the proximal location of the bone (r = -0.11 to 0.31). Tibiotarsal muscle CSA was also low to moderately correlated with biomechanical measures of bone quality (r = 0.20 to 0.41). Keel muscle CSA values were not correlated with keel BMD values, but they were correlated with biomechanical measures of tibiotarsal bone quality (r = 0.18 to 0.40). Keel CT measures of bone quality were not correlated with tibiotarsal CT measures of bone quality. At the proximal location, muscle CSA and tibiotarsal BMD were predictive of biomechanical failure load (F = 9.68, P = .0003muscle CSA; F = 9.13, P = .004tibiotarsal BMD). Findings supported using noninvasive CT measures of muscle and bone quality in longitudinal research studies evaluating the effects of interventions on laying hen welfare.

Influence of Perch-Provision Timing on Anxiety and Fearfulness in Laying Hens.

Perches can enhance laying hen welfare, but their effectiveness might be age-dependent. We investigated early and late perch access effects on anxiety and fear in pullets through attention bias (AB) and tonic immobility (TI) tests. Pullets (n = 728) were raised with or without multi-level perches: CP (continuous perch access: 0-37 weeks), EP (early perch access: 0-17 weeks), LP (late perch access: 17-37 weeks), and NP (no perch access). AB was conducted in weeks 21 and 37 (n = 84/week), and TI was performed in weeks 20, 25, and 37 (n = 112/week). CP hens fed quicker than EP, LP, and NP in AB at weeks 21 and 37 (p ≤ 0.05). CP and NP feeding latencies were stable, while EP and LP fed faster at week 37 (p ≤ 0.05). CP had the shortest TI at week 20 (p < 0.05). CP and LP had the shortest TI in weeks 25 and 37 (all p ≤ 0.05). Unlike NP, CP reduced anxiety and fear. Adding perches during laying (LP) raised anxiety at week 21, adapting by week 37, and removing pre-laying perches (EP) worsened fear at weeks 20 and 25 and anxiety at week 21, recovering by week 37. Adding or removing perches prior to the lay phase increased fear and anxiety, an effect that disappeared by week 37 of age. Our study indicates that continuous perch access benefits animal welfare compared to no perch access at all.

Brown and white layer pullet hybrids show different fear responses towards humans, but what role does light during incubation play in that?

Good early life conditions are increasingly recognized as essential to animal welfare later in life. The use of light during incubation might improve coping capacities and welfare in later life in poultry, by more closely approximating chicken natural environments compared to the current conventional incubation in darkness. Previous studies showed that lighted incubation resulted in more lateralized chicks, a more pronounced daily behavior rhythm, earlier onset of melatonin rhythms, and lower stress reactions to various stressors after hatching. Most existing research, however, has been conducted on broilers, and little information on lighted incubation is available for laying hens. In the current research, Dekalb White and ISA Brown eggs were incubated in complete darkness or in a cycle of green 12 L:12D throughout incubation, and five fear of human tests were performed on the 387 chickens during the rearing phase. We expected dark-incubated chickens to show stronger fear responses than light-incubated chickens. That was only the case for one of 15 behavior measurements taken during the tests (p < 0.05). In addition, white layer hybrids are known to be flightier and more fearful than brown hybrids. In this study, white chickens indeed showed stronger fear responses than brown chickens in 12 of the 15 behavior measurements (p ≤ 0.002). Furthermore, we expected light during incubation to have stronger effects on white chickens than on brown chickens, because of the stronger transmission of light through white eggshells. However, the interaction between hybrid and incubation was never significant (p ≥ 0.18). Finally, contrary to our expectations, there was no effect of the incubation treatments or the hybrid on plasma corticosterone responses to a manual restraint test (p ≥ 0.36). Since there was a hybrid effect on behavior in this test, it is reasonable to think that behavior reflected coping style, rather than fear level. To conclude, the light regime used in this study does not seem as promising as expected to improve laying hen welfare. Finally, the brown hybrid was usually less fearful than the white hybrid, though there were some exceptions depending on the stressor, and that should be taken into account in research and in laying hen management.

How are they really doing? Animal welfare on organic laying hen farms in terms of health and behaviour

ABSTRACT 1. The present study describes the current welfare situation on commercial organic laying hen farms in Sweden in terms of indoor environment, bird health and behaviour. 2. Organic laying hen farms (n = 11) in Sweden were visited for one day each. The farm visits were performed at the end of lay and involved farmer interviews, indoor environment assessments, behavioural observations and tests and clinical examinations in one flock per farm. 3. In 95% of all human avoidance distance test trials performed, the hens distanced themselves from the observer before the test was completed. Median number of birds per flock approaching during a novel object test (n = 4 trials per flock) was 2 (0-9). These results may indicate a high level of fear of humans and general fearfulness among the hens. 4. Plumage damage was especially prevalent and most severe on the breast and belly, tail and wings, with median prevalence of moderate-severe damage of 96% (84–100), 96% (72–100) and 98% (94–100), respectively. Median prevalence of keel bone deviations was 67% (32–84) with 3% fractures (0–8). Median prevalence of breast skin lesions was 57% (10–74). There was a significant positive association between breast skin lesions and keel bone deviations (P = 0.02) and foot pad hyperkeratosis (P < 0.001). Median prevalence of severe hyperkeratosis was 33% (8–96), with prevalence being significantly lower where litter depth was thicker (P = 0.003). More dust bathing events were observed in flocks where litter depth was thicker (P = 0.007). 5. The present study contributes with updated knowledge of laying hen welfare on organic farms in Sweden. The results confirm the findings of previous on-farm studies, demonstrating that important issues, including keel bone damage and severe feather pecking, remain in need of attention to ensure the welfare of laying hens in future commercial egg production.

Easier said than done! Organic farmers consider free-ranging important for laying hen welfare but outdoor areas need more shelter – important gaps between research and practice

ABSTRACT 1. The aim of the present study was to investigate the design and management of free-range areas and their use by birds on commercial organic laying hen farms in Sweden and to document farmers’ perspectives on outdoor access for poultry. 2. Eleven Swedish organic laying hen farms were visited. The farmers were interviewed about general farm management, bird health and behaviour and outdoor access. The free-range areas were assessed in terms of proportion covered by protective (high) vegetation and any artificial shelters provided. The numbers of hens ranging at different distances from the house were recorded twice during the day. 3. The outdoor area within 250m from the house contained 0–5% vegetation cover on six of the farms and at least 80% pasture on seven farms. On 10 farms, no more than 13% of the flock was observed outdoors. Of the hens observed in the free-range area, the median proportion ranging within 20m from the house or veranda per observation event was 99% (IQR=55–100%), confirming reports by the farmers. 4. Free-range access was considered important by all farmers, primarily for welfare reasons and most agreed that protective vegetation cover and/or artificial shelters were important in encouraging free-ranging. However, there was marked variation among the farmers in their suggestions on how to attract hens outside.

The Gordon Memorial Lecture: Laying hen welfare

ABSTRACT Preference tests remain a useful tool in the assessment of laying hen welfare and have been used to establish what types of resources and enrichments are most likely to meet the birds’ needs. Evidence on the underlying structure of bird preference suggests that hens make stable and reliable choices across time and context. This means that their preferences can also be used as a benchmark in the validation of other welfare indicators. Hens have sophisticated cognitive abilities. They are quick to form associations between events and they are flexible in how they apply their knowledge in different contexts. However, they may not form expectations about the world in the same way as some mammalian species. Limited research in this area to date seems to show that hens judge situations in absolute terms rather than evaluating how a situation may be improving or deteriorating. The proportion of hens housed in cage-free systems is increasing globally, providing birds with greater behavioural freedom. Many of the problems associated with cage-free systems, such as keel bone fractures, mortality and injurious pecking, are slowly reducing due to improved experience and appropriate changes in rearing practices, diet, housing design and alignment of breeding goals. However, much remains to be done. The design and performance of veranda-based systems which provide hens with fresh air and natural light is a promising avenue for future research aimed at optimising hen welfare and improving sustainability.

Green light during incubation: Effects on hatching characteristics in brown and white laying hens

Providing light during incubation is being investigated as a method to improve welfare in later life in poultry. This incubation method would more closely approximate chicken natural environment compared to the current incubation in darkness. Previous studies showed promising results of light during incubation on broiler welfare, but little is known about effects of light during incubation on laying hens. Especially, information about its effects on hatching characteristics (hatch time, hatchability, chick quality, body weight and embryonic age of death) is scarce and requires investigation in both white and brown egg layers. In the current study, Dekalb White (DW) and ISA Brown (ISA) eggs were incubated in complete darkness (dark) or in a light:dark cycle of 12L:12D throughout incubation (light), resulting in four treatment groups: DW-dark, DW-light, ISA-dark, and ISA-light. In the light treatments, green LEDs of 520 nm wavelength were used, at an intensity of 400 lux. First, light transmission through the eggshell was measured through 27 eggs. Then, an analysis of the effects of light during incubation on hatching characteristics was performed on 711 chicks in two consecutive experimental rounds. Light transmission was higher through white eggshells than through brown eggshells (N = 27, p < 0.001). Light during incubation had no effects on hatching characteristics (N = 711, p ≥ 0.1). Despite the difference of light transmission through eggshell between hybrids, there was no interaction between incubation treatment and hybrid on hatching characteristics (N = 471, p ≥ 0.06). Hatch time was longer and navel quality was better in DW than in ISA, while body weight and embryonic age of death were lower in DW than in ISA (all p < 0.001). Males and females had similar chick quality scores except for the beak quality, which was better for males (N = 486, p = 0.003). To conclude, green light during incubation did not negatively affect hatching characteristics in either DW nor ISA laying hen hybrids. Future research should therefore focus on its potential benefits for laying hen welfare.

Effects of different cage sizes and nest settings on laying hen nesting behavior and the proportion of dirty eggs in furnished cages

Furnished cages may promote laying hen welfare more than the traditional cage, but the high proportion of dirty eggs in the furnished cage system could directly affect the exterior quality of eggs, reducing the economic advantage of the furnished cage production system. The problem of the high proportion of dirty eggs reveals defects in the design of the cage, and it may also indicate competition among hens, affecting the utilization of nests. The research aimed to examine the effects of cage size, nest location, and degree of enclosure on behavioral adaptation and the proportion of dirty eggs. Nine hundred laying hens (Hy-line Brown) were housed in cages with eight different types of nests, and the experiment began at the 18 weeks of age and ended at week 38. The proportion of dirty eggs and the nesting behavior of hens were recorded. The number of nest visits and the sitting behavior of the hens in the medium furnished cage were significantly higher than in the large furnished cage (visits: P < 0.01; sitting: P < 0.01). The number of nest visits in the higher nests was significantly greater to lower nests (P = 0.01). The number of nest visits in the enclosed type nests was significantly higher than in the open type nests (P = 0.01). The cage size, nest location, and amount of enclosure had no significant effect on the proportion of dirty eggs (P > 0.05). In conclusion, the enclosed nests in a higher location were more attractive for laying hens.

Evaluation of laying hen breeding conditions on the farm and egg quality in the cage and cage-free systems in the period after the peak of laying

The study aimed to examine laying hens in the cage and cage-free breeding systems, the quality of table eggs and energy consumption in the hall after the peak of laying. In the research, the following were investigated and statistically evaluated welfare of laying hens Bovans Brown was monitored in three different rearing systems based on resources and animals. The research was designed into the post-peak laying period, at the age of laying hens from 34 to 47 weeks and a rearing system of enriched cages on deep litter and in aviaries. Statistical analyses of the measured data of the established indicators were performed with the SAS program package, version 8.2, for statistical characteristics, significance, and correlation relations. The proportion of laying hens dying was lower in aviaries compared to cages and on deep litter (p ≤0.05); in cages and on deep litter was comparable (p ˃0.05). The weight of laying hens was comparable (p ˃0.05). Feed consumption per hen, day, and egg was highest on deep litter (p ≤0.05). The proportion of eggs with a cracked shell and contaminated with dropping was highest on litter (p ≤0.05). Energy consumption in the hall expressed per layer and day was comparable in all three breeding systems (p ≤0.05). Among some selected indicators of laying hen welfare, egg quality and energy consumption in the hall during breeding and correlation relations (p ≤0.05) were statistically significant within individual breeding systems. The question of laying hen welfare and improving cage-free systems because of the adopted legislation banning breeding in a cage system requires further research to adopt best practices regarding resource-based, management- and animal-based parameters. Based on the results about welfare conditions, including energy consumption in halls and egg quality, it is an open question for comprehensive, interdisciplinary research.

PSXIII-5 Effects of Stocking Density on the Welfare and Immune Responses of Laying Hens Housed in Small Furnished Cages

Abstract To investigate the effects of stocking density on the welfare and immune responses of laying hens housed in furnished cages, 192 Hy-Line Brown hens were housed in small furnished cages and randomly divided into three groups on their 18 weeks old for low-density group (833 cm2 per hen, LD), medium-density group (625 cm2 per hen, MD), and high-density group (500 cm2 per hen, HD). There are eight cages in each stocking density. The welfare of laying hens was assessed at 22, 42 and 72 weeks of age (WOA) for feather quality, foot cleanness, footpad dermatitis, hyperkeratosis and keel bone damage. After the last welfare assessment, venous blood from the wing of the hen was extracted for testing immune indicators of Immunoglobulin Y (Ig Y), Interferon gamma (IFN-γ), Transforming growth factor beta (TGF-β), Interleukin-2 (IL-2), Interleukin-4 (IL-4), Interleukin-6 (IL-6), Interleukin-12 (IL-12) by enzyme-linked immunosorbent assay (ELISA). Results showed that feather quality of laying hens from HD group was worse than hens from LD and MD groups at 42 and 62 WOA (P &amp;lt; 0.05). The foot cleanness score of hens from HD group was worse than other two group hens at 62 WOA (P &amp;lt; 0.05), respectively. There was no significant difference between three groups on other welfare indicators (P &amp;gt; 0.05), but the welfare quality of laying hens got worse with the aging of laying hens. Laying hens from LD group had greater concentrations of serum IFN-γ, IL-2, IL-6 compared with hens from MD and HD groups (P &amp;lt; 0.05). There was no significant difference for other immune responses (P &amp;gt; 0.05). These findings suggest that keeping a high stocking density of laying hens could cause feather damage, impact the welfare quality and reduce the immune responses of laying hens housed in small furnished cages.

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.

Effect of Providing Environmental Enrichment into Aviary House on the Welfare of Laying Hens.

This study aimed to determine the effects of providing environmental enrichment materials-pumice stone and alfalfa hay-to laying hens in the aviary system. A total of 2196 40-week-old Hy-Line Brown laying hens were randomly allotted to three treatment groups: (1) no enrichment (control; CON), (2) enrichment with pumice stone (PS), and (3) enrichment with alfalfa hay (HAY). Each treatment comprised four replicates of 183 hens each, and four of the same materials were provided per replicate. The experiment lasted for 26 weeks. Feed and water were provided ad libitum. As a result, the PS and HAY groups demonstrated increased egg production (p &lt; 0.001). The HAY group showed a reduced rate of mislaid eggs (p &lt; 0.01) and produced low egg weight and pale-yellow yolk (p &lt; 0.05). Both enrichment materials decreased blood creatinine (CRE) or lactate dehydrogenase (LDH) in the blood and resulted in a significantly lower corticosterone (CORT) level (p &lt; 0.05). However, the feather condition scores for the laying hens were similar across all treatments (p &gt; 0.05). In summary, although pumice stone and alfalfa hay are effective in alleviating stress and improving the production of laying hens, additional environmental improvement studies are needed to contribute to reducing pecking behaviors in poultry farming.

Environmental enrichment in commercial flocks of aviary housed laying hens: relationship with plumage condition and fearfulness

Management strategies can have positive effects on laying hen welfare, including prevention of damaging behavior, aggression, and fear, particularly by using environmental enrichment (EE). However, few studies have investigated the effects of the provision of EE in commercial aviary flocks. This knowledge gap is particularly significant considering the increasing numbers of non-beak trimmed hens worldwide kept in aviaries. The aim of this study was to survey and investigate the relationship between commercially applied EE and plumage condition and fearfulness in Norwegian flocks of loose-housed laying hens. Forty-five indoor multi-tiered aviary-system flocks of laying hens from across Norway were visited at the end of lay (range: 70–76 wk of age). The flocks consisted of either Lohmann LSL (n = 30) or Dekalb White (n = 15) non–beak-trimmed hens. During the visit, the researchers collected data on the farmers’ use of the following five types of enrichment: pecking stones, gravel, oyster shells, grains scattered in the litter, and “toys”. Feather loss was assessed individually in approximately 50 hens per flock and scores were awarded using a 3-point scale (0–2) for each of the following body parts: head, back/wings, breast, and tail. Finally, a novel object test was performed in 4 different locations in each house. The results showed that damage to the tail feathers was correlated positively to the first age of provision of toys (Pearson correlation coefficient = 0.41; P = 0.051) and negatively to the amounts of gravel stones provided (Pearson correlation coefficient = −0.43, P = 0.02). No other associations between the welfare indicators and the provision of EE objects were found, likely because of the low variation of enrichment provision. The present study showed that the provision of EE objects such as toys and gravel stones can have significant benefits to the condition of laying hen plumage. This study also adds to the body of literature supporting the importance of early life experiences on the behavioral development of laying hens and on their welfare at older ages.

Effect of Transport Crate Position on Welfare of Laying Hens and Oxidative stress

This study was carried out to investigate the effects of crating position of laying hens during transport on live weight loss, mortality rate, plasma biochemical, and oxidative stress parameters under commercial transport conditions in Afyonkarahisar. A commercial multi-decked and fixed-crate-type poultry transport trailer was used for bird transportation. The hens were transported in 9 selected loading positions on the trailer's front, center, rear sections, and top, middle, and bottom rows. Both pre-transport and post-transport hens were weighed individually, and blood samples were taken. Live weight loss, mortality rate, glucose, MDA, AOA, and cortisol concentrations increased, triglyceride and cholesterol concentrations decreased in the hens transported between farm and slaughterhouse. The hens loaded in the bottom row and rear section were most adversely affected by transportation and, the welfare loss of these hens was dramatic. It has been observed that the microclimate conditions of the transport crates in the bottom row are more unfavorable than those in the other positions. The results showed that transport crates positioned in the bottom row and rear section of the trailer were more stressful for laying hens. In conclusion, the potential stress profile of the position of the animal crates during transport can contribute to the strategic solutions to be developed to reduce the welfare losses of laying hens.

Influence of Different Light Spectrums on Behaviour and Welfare in Laying Hens.

Simple SummaryThis study investigated how different types of lighting affect laying hen behaviour and welfare. Amount and quality of light are important for birds to perform their natural behaviours, e.g., find food and water, recognise conspecifics and safely navigate their environment. The lighting used in poultry production facilities differs considerably from light conditions in the natural environment in which domestic fowl have evolved, which might have negative consequences for their welfare. This study examined whether light closely resembling natural daylight and light found in forest understory in Southeast Asia (ancestral habitat of jungle fowl) affected the behaviour of laying hens. The results revealed that birds had a preference for natural lighting in some situations. It is likely that these effects were due to the presence of ultraviolet light, which is known to be important for visual performance in birds. However, the differences were rather small, indicating that sufficient light intensity and other quality factors in the housing environment are more important in maintaining high welfare than the specific spectral composition of the light. This new knowledge can be used to improve the housing environment of domestic fowl by supplying artificial spectrums replicating natural lighting.Artificial commercial lighting used in animal production facilities can have negative influences on visual abilities, behaviour and welfare of domestic fowl. This study examined the effects of natural-derived light spectrums on behaviour, production and welfare of laying hens reared from hatching into adulthood. Comparisons were made of frequency of a range of behaviours associated with activity, aggression and comfort in birds kept in control light (commercial standard), daylight (full spectrum, including ultraviolet (UV) wavelengths and forest light (forest understorey, including UV). In addition, bird preferences for different lights, feather damage and egg production were monitored. The results showed that the behavioural repertoire of birds changed with age, while the effects of light treatment were subtle. Some evidence was found that birds preferred either daylight or forest light to control light, suggesting that inclusion of UV contributed to the preference. Daylight and forest light were associated with more active behaviours, and daylight with better plumage and later start of lay. Thus natural-like light may have beneficial effects on domestic fowl, but the differences between broad-spectrum light sources are rather small.

Modulation of Stocking Densities in California Cages to Enhance the Production and Welfare of Commercial Laying Hens

Modulation of Stocking Densities in California Cages to Enhance the Production and Welfare of Commercial Laying Hens

Cage production and laying hen welfare

Although many factors affect the welfare of hens housed in cage and non-cage systems, welfare issues in cage systems often involve behavioural restrictions, whereas many welfare issues in non-cage systems involve health and hygiene. This review considers and compares the welfare of laying hens in cages, both conventional and furnished cages, with that of hens in non-cage systems, so as to highlight the welfare implications, both positive and negative, of cage housing. 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 has indicated that hens in conventional and furnished cages have lower (or similar), but not higher, levels of stress on the basis of glucocorticoid concentrations than do hens in non-cage systems. Furthermore, caged hens, generally, have lower mortality rates than do hens in non-cage systems. However, the behavioural repertoire of laying hens housed in conventional cages is clearly more compromised than that of hens in non-cage systems. In contrast to conventional cages, furnished cages may provide opportunities for positive emotional experiences arising from perching, dust-bathing, foraging and nesting in a nest box. Some have suggested that the problems with modern animal production is not that the animals are unable to perform certain behavioural opportunities, but that they are unable to fill the extra time available with limited behaviours when they have no need to find food, water or shelter. Environmental enrichment in which objects or situations are presented that act successfully, and with a foreseeable rewarding outcome for hens by also providing regular positive emotional experience, is likely to enhance hen welfare. Research on cage systems highlights the importance of the design of the housing system rather than just the housing system per se.

Non-infectious diseases and laying hen welfare

Numerous non-infectious conditions can affect commercial layer flocks. Some of these, such as conditions related to bodyweight, fatty liver haemorrhagic syndrome and effects of age are common to all production systems, while some are more common in cage systems (cage layer fatigue, feather pecking) or in cage-free systems (grass impaction, smothering, sunlight exposure, cannibalism, predation and injuries). Many of these conditions are covered in other papers and will not be dealt with in here. In the present paper, emphasis will be placed on grass impaction, smothering, effects of age, exposure to high light intensities, predation and conditions related to overweight/obesity issues. All of these are of considerable welfare concern for the industry. Grass impaction is a particular issue when hens are first released to the range areas and are exposed to vegetation or other fibrous materials. Mortality can be high with this problem. Smothering episodes can be generated by sudden flock disturbances, or from overcrowding in nests or related to nest-box design. Other less well understood triggers for smothering are poorly understood but have been linked to temperature variability, retreating shade in range areas on sunny days, dust-bathing opportunities and things that attract birds to certain points in the shed. The incidence of tumours increases with hen age. Most frequently encountered tumours are leiomyomas and adenocarcinomas, both of which are associated with the reproductive tract and are presumably linked to selection for higher and more sustained egg production. The incidence of these neoplastic conditions will need better understanding if increases in flock persistency of lay are desired. Light intensity is understood to be a possible trigger of increased aggressive behaviour and can lead to increased feather pecking and cannibalism. Predation, while frequently reported, is not regarded as a major cause of loss in most farming circumstances, although individual cases can be serious and it is a major cause of concern. Obesity is becoming more recognised as a problem in layer flocks as research begins to focus on its effects. Reduction in average flock weights will be an objective for further improvement in persistency of lay in the future.