Keel Bone Damage Research Articles

Rearing laying hens: Early environmental complexity and genetic strain have life-long effects on keel bone size and fractures

Keel bone damage (KBD) is a major welfare concern for laying hens. Environmental complexity during rearing is suggested to promote skeletal development and reduce KB fractures (KBF). We investigated the effect of rearing environment and genetic strain on KB development and health. Three consecutive replicate flocks of brown (B) and white-feathered (W) layer chicks (3000/ flock) were raised in three styles of rearing aviaries of Low,Mid, or High complexity and in conventional cages (Conv). Pullets from flocks 1 and 3 (1080/ flock) were subsequently housed in 24 furnished cages of two sizes (small: 30 vs large: 60 birds) for lay. Samples of pullets and hens were assessed as follows: Dissections at six, 11, and 16 WoA in flocks 1 and 2 for KB size, radiographs at 30, 50, and 70 WoA in flocks 1 and 3, for KBD and dissections at 70 WoA in flock 3 for KBD.Rearing complexity affected KB size of pullets (Conv < High < Mid, Low; P< 0.0001). W pullets had larger keels than B when adjusted for body weight throughout rearing (strain x age P= 0.005) and at 70 WoA (P< 0.001). KBF prevalence at end-of-lay was affected by rearing complexity (High < Low, Conv, P= 0.002). During lay, KBF severity was affected by rearing complexity (High < Low, Mid; P= 0.007), strain (W < B; P< 0.0001) and age (30 < 50 < 70 WoA; P< 0.0001). At 70 WoA, an interaction of rearing by strain affected KBF severity (most severe: B-Conv, least severe: B-Mid and W-High, P= 0.003). KBF severity scores from radiographs and dissections corresponded moderately (r= 0.547, P< 0.0001). The severity of KB deviations was affected by the size of the furnished cages (large > small, P= 0.049).In conclusion, rearing complexity and strain affected KB size and fracture severity and prevalence. These data confirm that complex rearing aviaries that are known to promote exercise reduce KBF severity and prevalence throughout lay.

Association of keel bone morphometry with keel bone damage and skeletal quality in the laying hen

ABSTRACT 1. The aim of this work was to identify a heritable keel bone phenotype with a correlation to keel bone damage and/or skeletal bone strength that could be easily measured in the living hen to aid selection to prevent welfare issues. 2. The scoring system used reflected the observed damage, keel bone dimensions and shape compared to traditional measurements of bone quality. 3. Increased keel bone damage was associated with poor humerus and tibia breaking strengths (p < 0.01). Bone damage was associated with higher whole keel density (p < 0.01) due to the effect of callus formation. 4. Keel bone depth and area was moderately heritable at indices of 0.32 and 0.40, respectively. Keel bone depth was genetically correlated with tibia (0.36) and humerus density (0.68) and keel bone area was correlated with humerus density (0.59). Deeper keel bones and those with larger areas had small, negative phenotypic correlations with keel bone damage (−0.07 and −0.11, respectively). The second principal component of keel bone shape represented the caudal section of the keel bone and cranial edge concavity. The third principal component represented the differences in the caudal tip of the keel bone, the concavity of the dorsal edge and convexity of the ventral edge. Heritability estimates were 0.44 and 0.39, respectively. 5. The results suggested that genetics contribute to morphometric traits. Hens with poorer skeletal quality are likely to accumulate more damage. Some of the traits may be a predictor of damage, although mid keel depth or concavity may simply reflect the effect of damage or deviation.

Comparisons of longitudinal radiographic measures of keel bones, tibiotarsal bones, and pelvic bones versus post-mortem measures of keel bone damage in Bovans Brown laying hens housed in an aviary system.

Keel bone damage, include deviations and fractures, is common in both white and brown laying hens, regardless of the housing system. Radiography for assessing birds' keel bones is was proposed by previous studies. However, radiographs show only 2 out of 3 dimensions of the dissected keel bones. The current study aimed to (1) investigate the association of radiographic optical density (keel and tibiotarsal) and geometry (keel) with dissected keel bone pathology. Previous studies suggested that keel bone fractures may result from internal pressure exerted by pelvic cavity contents. The current study also aimed to (2) investigate the potential associations between pelvic dimensions and measures of keel bone damage. A sample of 200 laying hens on a commercial farm were radiographed at 16, 29, 42, 55, and 68 weeks, and culled at the end of the laying period (week 74). The birds were examined post-mortem for pelvic dimensions and underwent whole-body radiography, followed by keel and tibiotarsal bone dissection and radiography, and keel bone scoring. The radiographs were used to estimate radiographic optical density (keel and tibiotarsal bone) and keel bone geometry (ratio of keel bone length to mid-depth). The method for on-farm radiography of laying hens, including live bird restraint, positioning for live keel imaging, and post-imaging measurements, was developed, tested, and found to be reproducible. The radiographs (1,116 images of 168 birds) and the respective measurements and post-mortem scores of keel bones are also provided for further development of radiographic metrics relevant to keel bone damage. Some longitudinal radiographic measurements of keel geometry (ratio of length to mid-depth) and optical density (keel and tibiotarsal) showed associations with the damage (deviations/fractures) observed on the dissected keel bones. The associations of keel damage were clearer with the radiographic keel geometry than with keel and tibiotarsal optical density, also clearer for the keel deviations than for keel fractures. The higher radiography ratio of keel length to mid-depth at weeks 42, 55 and 68 of age, the larger deviations size observed on the dissected keels at age of 74 weeks. The higher the tibiotarsal radiographic optical density at week 55 of age, the lower deviations size and fractures count observed on the dissected keels at age of 74 weeks. Pelvic dimensions showed a positive correlation with body weight, but a larger pelvic cavity was associated with increased keel bone damage. These findings lay the foundations for future use of on-farm radiography in identifying appropriate phenotypes for genetic selection for keel bone health.

Research Note: A deep learning method segments chicken keel bones from whole-body X-ray images

Most commercial laying hens suffer from sternum (keel) bone damage including deviations and fractures. X-raying hens, followed by segmenting and assessing the keel bone, is a key to automating the monitoring of keel bone condition. The aim of the current work is to train a deep learning model to segment the keel bone out of whole-body x-ray images. We obtained full-body x-ray images of laying hens (n = 1,051) and manually drew the outline of the keel bone on each image. Using the annotated images, a U-net model was then trained to segment the keel bone. The proposed model was evaluated using 5-fold cross validation. We obtained high segmentation accuracy (Dice coefficients of 0.88-0.90) repeatably over several validation folds. In conclusion, automatic segmentation of the keel bone from full-body x-ray images is possible with good accuracy. Segmentation is a requirement for automated measurements of keel geometry and density, which can subsequently be connected to susceptibility to keel deviations and fractures.

Utilizing 3-dimensional models to assess keel bone damage in laying hens throughout the lay cycle

The global egg industry is rapidly transitioning to cage-free egg production from conventional cages. Hens housed in cage-free systems have an increased prevalence of keel damage that could lead to reduced egg production and compromised well-being. The objective of this study was to determine the effects of dietary supplementation of n-3 fatty acids and vitamin D3 on keel damage in hens housed in multi-tier aviary systems (AV). Brown hens were placed in 4 AV system rooms after rearing at 17 wk of age (woa) with each room containing 576 birds. At 12 woa, rooms were randomly assigned to a dietary treatment of flaxseed oil, fish oil, vitamin D3, or control. Focal birds (36 per treatment) were longitudinally examined for keel damage using quantitative computed tomography (QCT) at nine timepoints from 16 to 52 woa. Three-dimensional digital twins of the keels were created from the QCT scans and visually assessed for damage. An overall keel severity score was recorded as well as the location, direction, and severity of each deviation or fracture. Severity was ranked on a 0 to 5 scale with 0 being no damage and 5 being severe. Damage scores were analyzed utilizing odds ratios with main effects of age and treatment. At 16 woa, 80% of hens had overall keel scores of 0 and 20% had scores of 1. At 52 woa, all hens had damage, with 31% having a score of 1, 61% scored 2 to 3, and 8% scored 4 to 5. Most fractures were not observed until peak lay. Dietary treatments did not affect likelihood of fracture incidences, but younger birds had lower odds of incurring keel fractures than older birds (P < 0.0001). The initial incidences of keel deviations occurred earlier than fractures, with most birds obtaining a keel deviation by 28 woa. Keel damage was not able to be prevented, but the age at which keel fractures and deviations initiate appear to be different, with deviations occurring during growth and fractures during lay.

Factors associated with keel bone damage – a longitudinal study of commercial layer flocks during the laying period

ABSTRACT 1. Keel bone damage, such as deformations and fractures, is a severe problem regarding animal welfare in layers. To identify risk factors under commercial conditions, 33 layer flocks (22 barn, 11 free range) with white (n = 18), brown (n = 11) and mixed (n = 4) genotypes were examined. 2. Keel bone status was frequently scored by palpation throughout the laying period. Data on housing and management conditions were collected. Multiple regression and Generalized Estimating Equations procedure were used for analysis. 3. At 65–74 weeks of age, the prevalence of keel bone damage ranged between 26% and 74%. White genotypes and those kept in multi-tier systems developed significantly (p < 0.05) more keel bone damage than brown genotypes or those kept in single-tier systems. Wing feather condition was associated with keel bone damage (p < 0.05), while other investigated variables regarding health, housing and management were not associated. 4. In conclusion, housing and management should be adapted to meet the birds’ specific needs in multi-tier systems, which may vary for brown and white genotypes. Whether those differences result from genotype associated predispositions or other individual traits remains to be determined.

Japanese quails (Coturnix Japonica) show keel bone damage during the laying period-a radiography study.

Keel bone damage is an important welfare issue in laying hens and can occur with a high prevalence of up to 100% of hens within one flock. Affected hens suffer from pain. Although multiple factors contribute to the prevalence and severity of keel bone damage, selection for high laying performance appears to play a key role. With up to 300 eggs/year, Japanese quails show a high laying performance, too, and, thus, may also show keel bone damage. However, to our knowledge, there are no scientific results on keel bone damage in Japanese quails to date. Therefore, the aim of this study was to assess whether keel bone fractures and deviations occur in Japanese quails and to obtain more detailed information about the development of their keel bone during the production cycle. A group of 51 female quails were radiographed at 8, 10, 15, 19, and 23weeks of age. The X-rays were used to detect fractures and deviations and to measure the lateral surface area, length, and radiographic density of the keel bone. In addition, the length of the caudal cartilaginous part of the keel bone was measured to learn more about the progress of ossification. At 23weeks of age, quails were euthanized and their macerated keel bones assessed for fractures and deviations. Both keel bone deviations and keel bone fractures were detected in the Japanese quails. In the 23rd week of age, 82% of the quails had a deviated keel bone as assessed after maceration. Furthermore, there was a decrease in radiographic density, lateral surface area, and length of the keel bone between weeks of age 8 and 19. This could indicate a general loss of bone substance and/or demineralization of the keel bone. Our study shows that keel bone damage is not only a problem in laying hens but also affects female Japanese quails.

Effect of pullet rearing environment, strain and perch shape on perching behaviour, perching biomechanics, and keel bone damage in enriched-housed laying hens

Housing, including pullet rearing environment and enrichments, impacts the welfare of laying hens throughout their life. As the egg industry shifts towards alternative housing systems (furnished cages, aviary, free-run, and free range), an increase in keel bone damage has raised welfare and economic concerns. Keel bone damage leads to reduced egg production, reduced egg quality and pain in laying hens. Our study aimed to determine within enriched caged layers, which strains experience stable perching biomechanics, bone strength, and keel health depending on perch design and pullet rearing system used. A 2 ×2 ×2 randomized complete block design with repeated measures was used. Lohmann White or Lohmann Brown pullets were placed in either pullet cages or floor pens at hatch with access to either mushroom or round perches (n=9 replicates/treatments) and then transferred to an enriched battery at lay. Perching kinematics, body weights, and keel scores were evaluated every two months (2, 4, 6, 8, 10, 12, 14 and 16 months of age). Dual x-ray absorptiometry and bone breaking strength tests were used to assess femur and keel bone mineral content and density; keel bone damage severity was assessed via digital imaging post-mortem. Behaviour observations were conducted every two weeks from seven until 69 weeks of age. Lohmann Brown spent more time perching from two to six months of age, when the keel is more susceptible to damage. There was a positive correlation between severity of deviation present and forward and backward keel motion (r 0.24; P<0.001). All bone parameters were affected by strain. Keel and femur content (Femur 3.50 g; Keel 2.08 g; P<0.001), and density (Femur 0.23 g/cm2; Keel 0.10 g/cm2; P<0.001) were higher in Lohmann Brown in comparison to Lohmann White (Femur 0.18 g/cm2 and 2.60 g ±0.069; Keel 0.07 g/cm2 and 1.19 g). Measured bone parameters were not protective against severe KBD as Lohmann Brown had more severe deviations (P<0.01) and more fractures (P<0.01) than Lohmann White. Pullet rearing environment did not have any effect on keel bone damage scores (P>0.10). Round perches led to more severe KBD in comparison to mushroom perches (P<0.05). In conclusion, mushroom perches are preferable to round perches for laying hens housed in furnished cages due to reduced KBD and increased stability while perching. Lower incidences of KBD despite lower bone mineralization indicate Lohmann White birds are more readily suited to furnished cages in comparison to Lohmann Brown birds.

Presence of keel bone damage in laying hens, pullets and roosters of local chicken breeds.

In commercial laying hens, keel bone damage (KBD) is a severe health and welfare problem leading to pain, reduced mobility and decreased laying performance. Flocks of all production systems and hybrid lines can be affected. KBD is a multifactorial welfare issue and, among other factors, associated with a high laying performance which negatively affects the calcium deposit in the medullary bones. Therefore, mature hens of local breeds with much lower egg production than commercial hybrids may be expected to show less or even no keel bone damage. This study evaluates (i) the prevalence of KBD in local breeds, (ii) the difference in type and level of damages, and (iii) if roosters and pullets are also affected. In total, we palpated 343 mature hens, 40 pullets, and 18 roosters of 13 different local breeds and one commercial hybrid. The animals were kept on eight different farms in free-range or floor-housing systems. Our results showed that on average 44.2% of mature hens per local breed were affected by KBD (range: 11.1%-84.7%). We found deviation of less than 1 cm in 26.9%, deviations of more than 1 cm in 6.4% and palpable fractures in 23.8% of the mature hens of local breeds. The tip was damaged in 23.6% of the mature hens. Also, pullets and roosters were affected by KBD. Finally, we found that KBD also occurs in local breeds. Therefore, we conclude that even the low laying performance of local breeds does not prevent them from the occurrence of KBD.KBD in local breeds may rather be associated with genetics (breed) as well as management and housing. Thus, breeders of local breeds should include bone health as a selection trait. Owners of local breeds should also pay attention to the condition of the keel and ought to be trained about preventive measures.

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.

Effect of Different Cage Densities and Age on Keel Bone Damage and Some Hormones in Laying Hens

Effect of Different Cage Densities and Age on Keel Bone Damage and Some Hormones in Laying Hens

Shape and fractures of carina sterni in chicken genotypes with different egg deposition rates reared indoor or free-range

Commercial laying hens have high frequency of damage to the keel bone (KB), which causes negative effects on health and welfare. KB damage may consist in fractures (KBF) and deviations (KBD). The aim of the present study was to compare the KB shape, by means of Geometric Morphometric, and the occurrence of fractures in different chicken genotypes reared either free-range (FR) or in enriched cages. Moreover, the relationship between KB shape, genotype and rearing system was analysed. Sixty birds/genotype (2 Italian local breeds, Bionda Piemontese and Robusta Maculata, their crossbreeds with Sasso and Lohmann Brown) were used. All the hens fed the same commercial feed throughout the trial. Body weight, egg production, feed intake and mortality were recorded from 25 to 66 weeks of age. Ca intake (IN) and output (OUT) were estimated and Ca OUT/IN was calculated. FR affected the occurrence of KB deviations but not the shape, whereas the fractures were mainly affected by genotype. Local breeds had a lower prevalence of KBF with similar level of KBD but with different shapes. Crossbreeds seemed to be a suitable compromise between egg deposition rate and occurrence of KB damages.

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

Occurrence, causes and consequences of keel bone damage of laying hens

Occurrence, causes and consequences of keel bone damage of laying hens

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.

Associations of range use with individual behaviour, clinical welfare indicators, fear response and gastrointestinal characteristics of two laying hen hybrids

Access to an outdoor range provides laying hens with increased space and improved opportunities for performing natural behaviours. However, not all hens utilise the range to the same extent, and this may be associated with the welfare of the individual hen. The aim of this study was to assess if extent of range use was associated with several clinical welfare indicators, time budgets, measures of tonic immobility and gastrointestinal characteristics. One hundred twenty focal individuals (Bovans Brown, n = 60; Dekalb White, n = 60) randomly chosen from 12 pens of 100 hens (10 hens from each pen) were housed in accordance with the EU organic standards. Clinical welfare indicators including plumage condition, foot health, keel bone damage and body weight were assessed upon arrival at 18 weeks of age and again at 23, 28, 33 and 38 weeks of age. Over five three-day periods at corresponding weeks, hens received individual back marks for identification and behaviour was recorded by instantaneous scan sampling from 8:30–15:30 in the house and on the range. Behaviour recorded included comfort behaviours, drinking, dust bathing, eating, foraging, locomotion, nest use, pecking, perching, resting and standing. Frequency of passes through the pophole and duration of time outdoors were also determined through video observations. At 18 weeks of age a tonic immobility test was performed and number of inductions, latency to first head movement after induction and the duration of tonic immobility were recorded. At the end of the study (38 weeks of age), gastrointestinal tract morphology and contents were assessed. Individual range use varied, with hens differing in time spent on range, number of exits and consistency in these measures over time. Extent of range use was not associated with clinical welfare indicators nor fear levels as assessed by a tonic immobility test. Hens’ time budgets differed depending on where they spent most of their day, with hens utilising the range to a greater extent generally being more active (duration on range: foraging: P < 0.001, standing: P = 0.005; number of exits: locomotion: P < 0.001). Hens that utilised the range to a greater extent likely consumed more forage, as evident by the greater weight of pasture found in their crop and gizzard (P < 0.001), contributing to more developed gastrointestinal organs including the crop (duration on range: P = 0.004), gizzard (P < 0.001), and proventriculus (duration on range: P = 0.014). To conclude, the fear level and clinical welfare condition of the hens were not associated with extent of range use, unlike the time budgets and gastrointestinal characteristics.

Intraobserver repeatability for a standardized protocol to quantify keel bone damage in laying hens using discrete and continuous radiographic measures.

Sternal carina damage (keel bone damage, KBD) is an important welfare concern for laying hen producers and backyard flock owners. Quantitative radiographic measures of KBD severity are helpful for researchers who study causes for this problem and the effects of novel interventions. The objectives of the current retrospective secondary analysis study were to develop and test intraobserver repeatability for a standardized protocol to quantify three categories of radiographic KBD using open-source image analysis software and discrete and continuous variables. The standardized protocol was developed and evaluated using triplicate measurements of 470 keel bone radiographs that had been previously acquired for a prospective study. Intraobserver repeatability was assessed using intra-class correlation coefficient (ICC) and control chart methods. Based on control chart analyses, measures within the acceptable range of intra-observer variation using the standardized protocol were the number of complete cranial fractures (97.02%), incomplete cranial fractures (96.38%), complete caudal fractures (95.32%), incomplete caudal fractures (98.09%), cranial calluses (99.79%), and caudal calluses (98.09%); proportion of deviation (POD) measurements (97.87%); and angle of displacement (AOD) measurements (93.60%). Findings can be used as background to support future research studies on KBD in laying hens.

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.

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

Simple SummaryThe laying hen industry is shifting from cages to alternative housing systems (such as aviaries) to address societal concerns regarding animal welfare. However, it is important to understand the hens’ needs in these systems, in terms of space use and behaviour, to promote their welfare and avoid drawbacks. Therefore, we examined the effects of three different structural modifications (addition of ramps and/or removal of internal partitions) to increase the hens’ freedom of movement in a commercial aviary system. Higher freedom of movement resulted in positive effects on feather conditions and the possibility of choosing between the aviary tiers according to the hens’ preferences. Laying hen producers may therefore adopt some of these structural modifications in aviary systems to enhance the welfare of hens.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.

A tagged visual analog scale is a reliable method to assess keel bone deviations in laying hens from radiographs.

Laying hens often suffer from keel bone damage (KBD) that includes pathologies with different etiologies, like diverse forms of fractures and deviations. Since KBD is a problem in all countries and housing systems, methods for the assessment of deviations are urgently needed. Comparisons between genetic lines and between studies are important to detect underlying mechanisms. Field researchers often use palpation as a low-cost and feasible technique for the assessment of KBD. In contrast to palpation, radiography is effective and highly precise at least in detecting keel bone fractures. The aim of this study was to: i) develop a scoring system to assess keel bone deviations from radiographs, ii) to assess inter- and intra-observer reliability of this scoring system, and iii) to investigate whether fractures and deviations of the keel are correlated. In total, 192 hens were used for the investigation. Digital radiographs were taken and evaluated for all hens after slaughter. We developed a tagged visual analog scale with two extreme images as anchors and four intermediate tags, resulting in six images representing the range from "no deviation" to "highly deviated" on a 10 cm line. Eleven participants scored 50 radiographs of keels with varying degree of severity, whereas five images were scored twice to assess intra-observer reliability. Intraclass correlation coefficient for inter-observer reliability was 0.979 with a confidence interval of 0.968 < ICC < 0.987 (F49,268 = 54.2, p < 0.0001). Intraclass correlation coefficient for intra-observer reliability was 0.831 with a confidence interval of 0.727 < ICC < 0.898 (F54,55 = 10.8, p < 0.0001). Individual intra-observer reliability ranged from 0.6 to 0.949. The Spearman correlation showed a strong positive correlation of fractures and deviations (s roh= 0.803, p < 0.001). The tagged visual analog scale could be a reliable instrument for the scoring of keel bone deviations. Our results support the assumption that the majority of highly deviated keels suffer from fractures as well. Further research is needed to investigate the correlation of palpation scores with the evaluation on radiographs.