Control of landing flight by laying hens: implications for the design of extensive housing systems

Influence of keel impacts and laying hen behavior on keel bone damage

Keel bone damage, which presents as fractures and/or deviations of the keel, has been detected in laying hens housed in all types of systems. Factors leading to keel bone damage in hens housed with limited vertical space, such as those housed in furnished systems, are not well understood, and are the topic of this study. Ten focal hens from each of 12 furnished cages (4 rooms of 3 cages) were fitted with keel mounted tri-axial accelerometers. Their behavior was video recorded continuously over two 3-wk trials: the first when the hens were between 52 and 60 wk of age, and the second approximately 20 wk later. The integrity of each hen's keel was evaluated at the start and end of each 3-wk trial using digital computed tomography. We identified predominant behaviors associated with acceleration events sustained at the keel (collisions, aggressive interactions and grooming) by pairing accelerometer outputs with video data. For each recorded acceleration event we calculated the acceleration magnitudes as the maximum summed acceleration recorded during the event, and by calculating the area under the acceleration curve. A principle components analysis, which was used as a data reduction technique, resulted in the identification of 4 components that were used in a subsequent regression analysis. A key finding is that the number of collisions a hen has with structures in her environment, and the number of aggressive interactions that a hen is involved, each affect the likelihood that she will develop 1 or more fractures within a 3-wk time span. This relationship between hen behavior and keel fracture formation was independent of the magnitude of acceleration involved in the event. Observed behavior did not have an impact on the formation of keel bone deviations, further supporting reports that the mechanisms underlying the 2 types of keel bone damage are different.

Providing elevated structures in the pullet rearing environment affects behavior during initial acclimation to a layer aviary

Spatial abilities of hens are particularly sensitive to development during early life. Experiences in pullet housing may have lasting consequences on adult hens' movements in cage-free environments. We tested whether opportunities to access elevated spaces during rearing improved hens' use of a multitiered aviary. Female Dekalb White pullets were reared in either floor pens (FL), single-tiered aviaries (ST), or 2-tiered aviaries (TT; n = 5 pens/environment) through 16 wk of age. Rearing structures were replaced with identical multitiered aviaries at 17 wk. The distribution of the flock within the aviary and the vertical transitions of 10 focal hens/pen across the aviary were determined from videos recorded during their first (D1) and seventh (D7) day of aviary access, as well as at 19, 23, and 27 wk of age. Prevalence of floor eggs was recorded weekly from 17 to 28 wk of age. On D1, more ST and TT hens utilized the aviary during the daytime (P = 0.0077), made more vertical transitions when searching for a roosting spot in the evening (P = 0.0021), and maintained a consistent distance traveled during transitions compared to FL hens (P = 0.02). These differences disappeared by D7, except that ST and TT hens continued to roost on the highest perches of the aviary more (P < 0.0001) than FL hens through 27 wk of age. FL hens laid more floor eggs than ST and TT hens for the first 2 wk of lay (P < 0.0001). The majority (97.9%) of vertical transitions was controlled. Uncontrolled transitions were highest at D1 and decreased by D7 (P = 0.0009) and were not affected by rearing (P = 0.33). The results suggest that hens reared with minimal height are hesitant to use the laying hen aviaries when they are first transferred. They acclimate within 1 to 2 wk, but continue to roost less in the highest accessible level.

Biomechanics of landing in injured and uninjured chickens and the role of meloxicam

Birds use their legs and wings when transitioning from aerial to ground locomotion during landing. To improve our understanding of the effects of footpad dermatitis (FPD) and keel bone fracture (KBF) upon landing biomechanics in laying hens, we measured ground-reaction forces generated by hens (n = 37) as they landed on force plates (Bertec Corporation, Columbus, OH) from a 30 cm drop or 170 cm jump in a single-blinded placebo-controlled trial using a cross-over design where birds received an anti-inflammatory (meloxicam, 5 mg/kg body mass) or placebo treatment beforehand. We used generalized linear mixed models to test for effects of health status, treatment and their interaction on landing velocity (m/s), maximum resultant force (N), and impulse (force integrated with respect to time [N s]). Birds with FPD and KBF tended to show divergent alterations to their landing biomechanics when landing from a 30 cm drop, with a higher landing velocity and maximum force in KBF compared to FPD birds, potentially indicative of efforts to either reduce the use of their wings or impacts on inflamed footpads. In contrast, at 170 cm jumps fewer differences between birds of different health statuses were observed likely due to laying hens being poor flyers already at their maximum power output. Our results indicate that orthopedic injuries, apart from being welfare issues on their own, may have subtle influences on bird mobility through altered landing biomechanics that should be considered.

Influence of Increased Freedom of Movement on Welfare and Egg Laying Pattern of Hens Kept in Aviaries

This work investigates the effects of structural modifications on the welfare level and laying patterns of hens in a three-tier commercial aviary system. Four experimental groups were used: C (control, housed in a traditional aviary); LM (longitudinal movement, in which internal partitions were removed); VM (vertical movement, in which ramps were installed); and FM (freedom of movement, both LM and VM modifications). Hens showed worse body condition scores (p < 0.05) in all the modified aviaries, while plumage condition was improved in FM but worsened in VM (p < 0.05). No significant effect was observed on egg deposition patterns, egg quality or keel bone damage. When ramps were available (VM and FM groups), hens reduced the number of flights and increased the number of walks from 0.52 to 7.7% of the displacements on average (p < 0.05). Apart from some feather pecking concerns in VM (likely due to overcrowding in some favourite aviary areas), LM and FM seemed to facilitate animal movement and promote species−specific behaviour. It is concluded that hen welfare in aviary systems can be improved by means of tailored structural modifications. Producers may therefore adopt some of these modifications (providing ramps and/or removing vertical barriers) to enhance the welfare of hens.

Domestic egg-laying hens, Gallus gallus domesticus, do not modulate flapping flight performance in response to wing condition

Wild birds modulate wing and whole-body kinematics to adjust their flight patterns and trajectories when wing loading increases flight power requirements. Domestic chickens (Gallus gallus domesticus) in backyards and farms exhibit feather loss, naturally high wing loading, and limited flight capabilities. Yet, housing chickens in aviaries requires birds to navigate three-dimensional spaces to access resources. To understand the impact of feather loss on laying hens' flight capabilities, we symmetrically clipped the primary and secondary feathers before measuring wing and whole-body kinematics during descent from a 1.5 m platform. We expected birds to compensate for increased wing loading by increasing wingbeat frequency, amplitude and angular velocity. Otherwise, we expected to observe an increase in descent velocity and angle and an increase in vertical acceleration. Feather clipping had a significant effect on descent velocity, descent angle and horizontal acceleration. Half-clipped hens had lower descent velocity and angle than full-clipped hens, and unclipped hens had the highest horizontal acceleration. All hens landed with a velocity two to three times greater than in bird species that are adept fliers. Our results suggest that intact laying hens operate at the maximal power output supported by their anatomy and are at the limit of their ability to control flight trajectory.

The impact of management, husbandry and stockperson decisions on the welfare of laying hens in Australia

The present review examines the impact of management and husbandry decisions on the welfare of laying hens in Australia. The literature on many of these aspects is lacking for the Australian egg industry, and, indeed, for the egg industry in general. Management decisions that can affect hen welfare relate to the initial farm design, husbandry routines, and staff selection and training. As modern laying houses represent a considerable financial investment, the decisions made during the design phase are likely to affect both the hens and stockpeople for substantial periods. Hens in cage systems may benefit from fewer tiers and greater space allowances. In non-cage systems, the brown genotypes used in the Australian egg industry may benefit from lower structures that accommodate their heavier and less agile bodies. Keel fractures can be reduced by improving the skeletal health and spatial cognition of laying hens during the rearing period, in addition to minimising the distances they need to jump when navigating aviary structures. The addition of a wintergarden to fixed free-range systems appears to be beneficial. Housing hens in mobile units on free-range farms may challenge their welfare, particularly in relation to heat stress. There is also room for improvement in biosecurity practices and health monitoring of hens, as these appear to be lacking at some farms. The current strains of hen used in free-range systems may not be best suited to these conditions, on the basis of their body condition and flock uniformity. Feed quality may also need to be monitored for quality assurance and optimal hen nutrition. Hen welfare during depopulation can be improved through staff training and by reducing staff fatigue. Euthanising spent hens on farm offers welfare benefits over transporting spent hens to an abattoir. Both hen welfare and working conditions for stock people should be considered when designing laying houses to provide suitable conditions for both hens and stockpeople. This will help improve the job satisfaction of stockpeople, which may translate into better care for the hens and may aid in retaining quality staff. Stockpeople must be recognised as vital contributors to hen welfare in the egg industry, and it is important for the egg industry to continue to attract, train and retain skilled stockpeople to ensure that they enjoy their job and are motivated to apply best-practice care for their flocks. Promoting the animal-care aspect of stockmanship in combination with a supportive managerial environment with optimal working conditions may increase the attractiveness of the egg industry as a place to work.

Skeletal health of layers across all housing systems and future research directions for Australia

Modern laying hens have been selected for an astounding rate of egg production, but the physiological calcium demand takes a significant toll on their skeletal health. Bones can be assessed both in vivo and ex vivo, using a combination of different structural and mechanical analysis methods. Typically, the properties of leg, wing and keel bones are measured. Conventional caged layers are restricted in movement, which imbalances structural bone resorption and new bone formation, resulting in osteoporosis. Hens within alternative housing systems have opportunities to exercise for strengthening bones, but they can also suffer from higher rates of keel fractures and/or deviations that are likely to have resulted from collisions or pressure force. Limited research has been conducted within Australian commercial housing systems to assess hen skeletal health, including prevalence of keel damage across different system types. Research conducted on both brown and white hen strains approximately within the past decade internationally (2009 onward) has shown that skeletal health is impaired across all housing systems. Keel-bone damage is of specific concern as it occurs at high rates, particularly in multi-tiered systems, is painful, can alter hen behaviour, and reduce both production and egg quality. Management strategies such as the provision of ramps to access perches and tiers can reduce the incidence of keel-bone damage to a degree. Bone strength can be improved through exercise opportunities, particularly when available during pullet rearing. Genetic selection for high bone strength may be necessary for hens to adequately adapt to loose-housed systems, but the best strategy for improving skeletal health is likely to be multifactorial.

A songbird inhibits blinking behaviour in flight

Visual attention plays a fundamental role in avian flight but attention is likely limited whenever birds blink. Because blinks are necessary to maintaining proper vision, this study tested the hypothesis that birds strategically inhibit their blinks in flight. The blinks of captive great-tailed grackles (Quiscalus mexicanus) were recorded before, during and after they flew a short distance in an open environment. The grackles spent the least amount of time blinking in flight (take-off, during flight and landing) and the most amount of time blinking at impact. Their blinking behaviour was similar before and after flight. These results suggest that grackles strategically inhibit their blinking behaviour in flight, potentially because blinks impose costs to avian flight.

Perch Positioning Affects both Laying Hen Locomotion and Forces Experienced at the Keel

The aim of this study was to assess the effect of perch positioning on laying hens' locomotion and the resulting energy experienced at the keel. Twenty Nick Chick and 20 Brown Nick hens were trained to transition from a platform to a perch in several configurations. Three variables of perch positioning were tested in a 2 × 2 × 2 factorial design: direction (upward vs. downward), angle (flat vs. steep), and distance (50 cm vs. 100 cm). All hens were tested for five jumps of each treatment combination at 27-28 weeks of age. As predicted, we found steep angles and long distances to result in higher peak forces and impulse during take-off, flight, and landing; longer latency to jump; a higher likelihood to perform balancing movements; and a longer latency to peck at the provided food reward. The effect of perch positioning on locomotion and force at the keel during downwards jumps and flight was more pronounced in Brown Nick hens than in Nick Chick hens. Although we cannot state how the observed forces at the keel relate to the risk for keel bone fractures, our results indicated that optimizing perch positioning can reduce accumulated forced at the keel and consequent risk for fracture due to unsuccessful transitions.

Later exposure to perches and nests reduces individual hens' occupancy of vertical space in an aviary and increases force of falls at night

Tiered aviaries are intended to improve laying hen welfare by providing resources that enable them to perform essential behaviors. However, hens must be able to navigate these complex systems efficiently and safely. This study investigated the influence of providing perches and nests starting at 17 or 25 wk of age (WOA) on hens' use of vertical space in an aviary at 36 and 54 WOA. Three treatments were applied to pullets raised in floor pens until 17 WOA (4 units/treatment; 100 hens/unit). Control (CON) pullets were placed into aviaries at 17 WOA. Floor (FLR) pullets were placed into aviaries at 25 WOA. Perches and nests were placed in enriched (ENR) pullets' floor pens at 17 WOA prior to moving ENR birds to aviaries at 25 WOA. Five focal hens/unit (n = 20 total hens/treatment) were fitted with accelerometers, and their diurnal movement (g) and frequency (n) and acceleration (g) of falls at night were recorded. Direct observation of focal hens was conducted for 6 min/hen at morning, midday, and evening for 3 consecutive days at 36 and 54 WOA, and location and time spent on vertical tiers were recorded. At 36 WOA, FLR hens spent more time on litter than CON and ENR, which spent more time in the top tier (all P ≤ 0.05). ENR hens exhibited higher vertical movement than CON and FLR hens (0.8, 0.6, and 0.3 g; P = 0.003). CON hens fell most often at night (16 vs. 9 FLR and 5 ENR), whereas FLR hens had higher acceleration and calculated collision force than CON and ENR hens during falls (0.8, 0.5, 0.3 g and 15, 10, 5 N, respectively; P ≤ 0.05). At 54 WOA, hens' movement and vertical distribution were similar across treatments. Delaying birds' access to perches and nests until 25 WOA impacted their movement, vertical space use, and falls at night for at least 10 wk. However, providing perches and nests at 17 WOA, even in floor pens, considerably mitigated such impacts.

A review of environmental enrichment for laying hens during rearing in relation to their behavioral and physiological development

Globally, laying hen production systems are a focus of concern for animal welfare. Recently, the impacts of rearing environments have attracted attention, particularly with the trend toward more complex production systems including aviaries, furnished cages, barn, and free-range. Enriching the rearing environments with physical, sensory, and stimulatory additions can optimize the bird's development but commercial-scale research is limited. In this review, "enrichment" is defined as anything additional added to the bird's environment including structurally complex rearing systems. The impacts of enrichments on visual development, neurobehavioral development, auditory stimulation, skeletal development, immune function, behavioral development of fear and pecking, and specifically pullets destined for free-range systems are summarized and areas for future research identified. Visual enrichment and auditory stimulation may enhance neural development but specific mechanisms of impact and suitable commercial enrichments still need elucidating. Enrichments that target left/right brain hemispheres/behavioral traits may prepare birds for specific types of adult housing environments (caged, indoor, outdoor). Similarly, structural enrichments are needed to optimize skeletal development depending on the adult layer system, but specific physiological processes resulting from different types of exercise are poorly understood. Stimulating appropriate pecking behavior from hatch is critical but producers will need to adapt to different flock preferences to provide enrichments that are utilized by each rearing group. Enrichments have potential to enhance immune function through the application of mild stressors that promote adaptability, and this same principle applies to free-range pullets destined for variable outdoor environments. Complex rearing systems may have multiple benefits, including reducing fear, that improve the transition to the layer facility. Overall, there is a need to commercially validate positive impacts of cost-effective enrichments on bird behavior and physiology.

Physical Health Problems and Environmental Challenges Influence Balancing Behaviour in Laying Hens

With rising public concern for animal welfare, many major food chains and restaurants are changing their policies, strictly buying their eggs from non-cage producers. However, with the additional space in these cage-free systems to perform natural behaviours and movements comes the risk of injury. We evaluated the ability to maintain balance in adult laying hens with health problems (footpad dermatitis, keel damage, poor wing feather cover; n = 15) using a series of environmental challenges and compared such abilities with those of healthy birds (n = 5). Environmental challenges consisted of visual and spatial constraints, created using a head mask, perch obstacles, and static and swaying perch states. We hypothesized that perch movement, environmental challenges, and diminished physical health would negatively impact perching performance demonstrated as balance (as measured by time spent on perch and by number of falls of the perch) and would require more exaggerated correctional movements. We measured perching stability whereby each bird underwent eight 30-second trials on a static and swaying perch: with and without disrupted vision (head mask), with and without space limitations (obstacles) and combinations thereof. Video recordings (600 Hz) and a three-axis accelerometer/gyroscope (100 Hz) were used to measure the number of jumps/falls, latencies to leave the perch, as well as magnitude and direction of both linear and rotational balance-correcting movements. Laying hens with and without physical health problems, in both challenged and unchallenged environments, managed to perch and remain off the ground. We attribute this capacity to our training of the birds. Environmental challenges and physical state had an effect on the use of accelerations and rotations to stabilize themselves on a perch. Birds with physical health problems performed a higher frequency of rotational corrections to keep the body centered over the perch, whereas, for both health categories, environmental challenges required more intense and variable movement corrections. Collectively, these results provide novel empirical support for the effectiveness of training, and highlight that overcrowding, visual constraints, and poor physical health all reduce perching performance.

Failed landings after laying hen flight in a commercial aviary over two flock cycles

Many egg producers are adopting alternative housing systems such as aviaries that provide hens a tiered cage and a litter-covered open floor area. This larger, more complex environment permits expression of behaviors not seen in space-limited cages, such as flight. Flight is an exercise important for strengthening bones; but domestic hens might display imperfect flight landings due to poor flight control. To assess the potential implications of open space, we evaluated the landing success of Lohmann white laying hens in a commercial aviary. Video recordings of hens were taken from 4 aviary sections at peak lay, mid lay and end lay across two flock cycles. Observations were made in each focal section of all flights throughout the day noting flight origin and landing location (outer perch or litter) and landing success or failure. In Flock 1, 9.1% of all flights failed and 21% failed in Flock 2. The number of flights decreased across the laying cycle for both flocks. Proportionally more failed landings were observed in the double row sections in Flock 2. Collisions with other hens were more common than slipping on the ground or colliding with aviary structures across sections and flocks. More hens slipped on the ground and collided with physical structures at peak lay for Flock 2 than at other time points. More collisions with other hens were seen at mid and end lay than at peak lay for Flock 2. Landings ending on perches failed more often than landings on litter. These results indicate potential for flight-related hen injuries in aviary systems resulting from failed landings, which may have implications for hen welfare and optimal system design and management.

Risk factors associated with keel bone and foot pad disorders in laying hens housed in aviary systems

Aviary systems for laying hens offer space and opportunities to perform natural behaviors. However, hen welfare can be impaired due to increased risk for keel bone and foot pad disorders in those systems. This cross-sectional study (N = 47 flocks) aimed to assess prevalences of keel bone and foot pad disorders in laying hens housed in aviaries in Belgium to identify risk factors for these disorders and their relation to egg production. Information on housing characteristics and egg production were obtained through questionnaire-based interviews, farm records, and measurements in the henhouse. Keel bone (wounds, hematomas, fractures, deviations) and foot pad disorders (dermatitis, hyperkeratosis) were assessed in 50 randomly selected 60-week-old laying hens per flock. A linear model with stepwise selection procedure was used to investigate associations between risk factors, production parameters, and the keel bone and foot pad disorders. The flock mean prevalences were: hematomas 41.2%, wounds 17.6%, fractures 82.5%, deviations 58.9%, hyperkeratosis 42.0%, dermatitis 27.6%, and bumble foot 1.2%. Identified risk factors for keel bone disorders were aviary type (row vs. portal), tier flooring material (wire mesh vs. plastic slats), corridor width, nest box perch, and hybrid. Identified risk factors for foot pad disorders were aviary type (row vs. portal), free-range, and hybrid. Percentage of second-quality eggs was negatively associated with keel bone deviations (P = 0.029) at the flock level. Keel bone and foot pad disorders were alarmingly high in aviary housing. The identification of various risk factors suggests improvements to aviary systems may lead to better welfare of laying hens.

Analysis of landing behaviour of three layer lines on different perch designs

1. The prevalence of keel bone deformities in laying hens is high and is partly associated with unsuitable perch designs, which impose a risk of injury due to an unstable footing. 2. Over two experiments, 9 or 10 hens of each of three layer lines (Lohmann Selected Leghorn (LSL), Lohmann Tradition (LT) and Lohmann Brown (LB)) were filmed while landing on three different perch types, including steel perches of various diameters, a commercial mushroom-shaped plastic perch and a newly developed prototype perch with a soft surface material. 3. Data on landing behaviour (safe vs. unsafe or failed landing) following downward jumps were collected for 25, 50 and 60 cm vertical distances and 75 cm horizontal distance between a wooden start perch and the different destination perches. 4. The highest proportion of safe landings occurred on the prototype perch, whereas least safe landings were observed on steel perches, irrespective of their diameter. The mushroom-shaped perch was intermediate with regard to the safeness of landing. 5. A threshold of 50 cm vertical distance (34° slope) was identified as the optimum for downward jumps on perches in order to reduce the risk of unsafe or failed landings. Above this threshold, the proportion of safe landings declined significantly. 6. Brown shell layer types (LB and LT) had a lower proportion of safe landings compared to the white shell layer type (LSL), whereas no difference was found between LB and LT layer lines. 7. Although steel perches prevail in commercial housing, these perches were found to be least advantageous with regard to landing behaviour. The prototype perch provided the most stable footing on perching and is a promising alternative to replace commercial steel perches, thus helping to reduce the risk of perch-related keel bone injury.

Poultry housing and husbandry

1. In order to conduct this anniversary review, 10 excellent papers were carefully selected from the 148 available papers published on housing and husbandry in British Poultry Science (BPS) over the past 50 years. 2. The 10 selected papers on this subject covered mainly the housing and husbandry of laying hens, but two of them dealt with various aspects of broiler production. 3. Aspects of housing considered included a wide range of intensive and extensive systems of broiler and egg production. Specific topics included the effects of husbandry system on bird welfare, including skeletal damage in laying hens and contact dermatitis in broiler chickens, as well as the design and management of nest boxes, perches, feeders and drinkers, conventional laying cages (CCs), furnished laying cages (FCs) and non-cage systems (NCs). 4. A variety of the findings in these and related papers have enlightened our understanding of many aspects of poultry housing and husbandry; most of them have found application in the poultry industry and thus improved its efficiency.

Providing laying hens with perches: fulfilling behavioural needs but causing injury?

1. The EU laying hen directive, which bans standard battery cages from 2012, has implications for animal welfare, particularly since housing laying hens in extensive systems, while increasing natural behaviour and improving bone strength, is associated with a greater level of bone fractures, predominantly of the keel bone, compared to birds housed in cages. 2. The aetiology and welfare consequences of keel and other bone fractures are not well understood and could have important implications for housing system designs. While proposed alterations to layer housing are based on the desire to fulfil behavioural needs and increase bone strength, there appears to have been little consideration of the effect of system on potential injury. 3. In addition, there are variations in how the directive is interpreted. For example, egg producers housing hens in extensive systems in Scotland and Northern Ireland must provide hens with aerial perches, whereas in England and Wales they do not. Aerial perches may be implicated in bone fracture injuries. 4. This paper reviews the prevalence of bone fractures in the egg-laying sector of the poultry industry and the literature on perches. It also explores how bone fractures may be occurring. 5. We propose some means of reducing bone fracture, namely through improved housing designs and genetic selection.