The Influence of Keel Bone Damage on Welfare of Laying Hens

Keel bone fractures affect laying hens' mobility, but no evidence for reciprocal effects

Keel bone fractures (KBF) are prevalent in commercial laying hens and are considered one of the greatest welfare concerns in the egg-production industry. While clear associations exist between KBF and animal mobility, suggesting that KBF impair mobility, the effect of mobility on KBF remains unclear. We combined data from three studies that assessed keel bone fracture severity through radiographs and monitored hens' transitions between different zones of a multi-tier aviary system (the three tiers, a littered floor, and a winter garden) the week prior to radiograph. For each hen, we extracted two daily movement behaviours: the vertical distance travelled and the mean number of zones crossed within one transition; and two daily space-use behaviours: the time spent in the top tier and the unevenness of time spent across zones. We used hierarchical Bayesian continuous time dynamic modelling to estimate how a change in a behaviour predicted a later change in keel bone fracture severity, and vice versa. Increased fracture severity did not predict later changes in space-use behaviours, but it did predict changes in movement behaviours. Specifically, increased fracture severity led to decreased vertical travelled distance and a tendency to cross more zones within one transition, suggesting impaired mobility in hens with increased fracture severity. In contrast, we found no evidence that movement or space-use behaviours predict later change in fracture severity, challenging previous literature suggesting that vertical locomotion through jumping and flying may exacerbate keel bone fractures in complex three-dimensional systems due to increased risk of collisions. However, similar efforts accounting for the location of fractures on the keel could unveil the potential influence of movement and space-use behaviours in the formation and change (healing or worsening) of KBF and increase our ability to mitigate their effects.

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.

ß-Hydroxy-ß-methylbutyrate: A feed supplement influencing performance, bone metabolism, intestinal morphology, and muscle quality of laying hens: a preliminary one-point study

Laying hens, selectively bred for high egg production, often suffer from bone fragility and fractures, impacting their welfare and causing economic losses. Additionally, gut health and muscle quality are crucial for overall health and productivity. This study aimed to evaluate the effects of ß-Hydroxy-ß-methylbutyrate (HMB) supplementation on performance, bone metabolism, intestinal morphology, and muscle quality in laying hens. Forty-eight Bovans Brown hens were divided into a control group and an HMB-supplemented group (0.02% HMB in diet). The study spanned from the 31st to the 60th wk of age. Assessments included bone mechanical testing, serum hormonal analysis, histological analysis of bone and intestine, and muscle quality analysis. The HMB supplementation led to decreased feed intake without affecting body weight or laying rate in laying hens. It caused an increase in both mean daily and total egg weight, indicating improved feed utilization, without influencing the feed intake to egg weight ratio. Enhanced bone formation markers and altered intestinal morphometric parameters were observed, along with improved trabecular bone structure. However, no changes in measured other bone quality indices, including geometric, densitometric, or mechanical properties were observed. Muscle analysis revealed no significant changes in overall meat quality, except for a decrease in cholesterol content and alterations in the fatty acid profile, notably a reduction in total n-3 polyunsaturated and total polyunsaturated fatty acids (PUFA). In conclusion, although not all effects of HMB supplementation were unequivocally beneficial, the positive changes in performance data and trabecular bone microarchitecture support further research into various doses and durations of supplementation. Such studies are necessary to fully understand and optimize the benefits of HMB for enhancing the health and productivity of laying hens.

Commercial hatchery practices have long-lasting effects on laying hens' spatial behaviour and health

The commercial hatchery process is globally standardized and exposes billions of day-old layer chicks to stress every year. By alleviating this early stress, on-farm hatching is thought to improve animal welfare, yet little is known about its effects throughout production. This study compared welfare indicators and spatial behaviours during the laying period of hens hatched in an on-farm environment (OFH) to those hatched in a commercial hatchery and transferred at one day-old to a rearing barn (STAN). In particular, we assessed how OFH and TRAN hens differed in space-use and movement behaviours following the transfer to the laying barn at 17 weeks of age, a similar stressor encountered by STAN hens early in life, and determined whether effects aligned more with the 'silver-spoon' or 'environmental matching' hypothesis. We found that for the first three months post-transfer into the laying barn, OFH hens, on average, transitioned less between the aviary's tiers and spent less time on the littered floor. Because OFH hens became behaviourally more similar to STAN hens over time, these results suggest that OFH hens required a prolonged period to establish their daily behavioural patterns. Furthermore, OFH hens had more severe keel bone fractures throughout the laying period but similar feather damage and body mass to STAN hens. No differences were found in hen mortality or the number of eggs per live hen. These findings support the environmental matching hypothesis and suggest that early-life stressors may have prepared hens for later-life stressors, underscoring the importance of both early-life and adult environments in enhancing animal welfare throughout production.

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.

Graded levels of Eimeria challenge altered the microstructural architecture and reduced the cortical bone growth of femur of Hy-Line W-36 pullets at early stage of growth (0-6 wk of age)

An experiment was carried out to evaluate the impact of mixed Eimeria challenge on skeletal health of Hy-Line W-36 pullets. A total of 540, 16-day-old pullets were randomly allocated into 5 treatment groups, including a nonchallenged control. A mixed Eimeria species solution containing 50,000 E. maxima, 50,000 E. tenella, and 250,000 E. acervulina oocysts per mL was prepared and challenged to 1 group as a high-dose treatment. The 2-fold serial dilution was done to prepare the medium-high (25,000 E. maxima; 25,000 E. tenella; 125,000 E. acervulina), the medium-low (12,500 E. maxima; 12,500 E. tenella; 62,500 E. acervulina), and the low (6,250 E. maxima; 6,250 E. tenella; 31,250 E. acervulina) dose treatments which were challenged to 3 corresponding groups, respectively. The mineral apposition rate (MAR) was measured from 0 to 14 d post inoculation (DPI) and 14 to 28 DPI using calcein injection. The microstructural architecture of the femur was analyzed using the Skyscan X-ray microtomography (microCT) on 6, 14, and 28 DPI. The results showed that the MAR decreased linearly with an increase in the challenged dose (P < 0.05) during 0 to 14 DPI. The results of microCT revealed that cortical and total BMD, BMC, bone volume (BV), and bone volume as a fraction of tissue volume (BV/TV) of femur decreased both linearly (P < 0.05). Conversely, the total number of pores increased linearly with an increase in challenge dosages on 6 and 14 DPI. Trabecular BMD, BV, BV/TV, trabecular number, and trabecular thickness decreased linearly with an increase in the challenge dosages (P < 0.05) on 6 DPI. Furthermore, Eimeria infection significantly increased the number of osteoclasts and osteoclastic activity (P = 0.001). The result of this study suggests that the mixed Eimeria challenge negatively impacts the quality of skeletal health in a linear or quadratic manner with an increase in the concentration of Eimeria oocysts. The negative impact on long bone development might be due to malabsorption, nutrient deficiency during the infection, along with oxidative stress/inflammation disrupting the balance of osteoblastic and osteoclastic cells and their functions.

The cheese paradox: How do vegetarians justify consuming non-meat animal products?

Researchers interested in animal ethics have proposed the 'meat paradox' - psychological discomfort arising from people's affinity for animals and conflicting desire to consume their flesh. Yet what can be said about the psychology of consuming an animal's non-meat products, in an age where most beings in these industries are harmed, and ultimately killed? Non-meat animal products (NMAPs) such as eggs and dairy entail the same, and perhaps even worse ethical issues as meat yet receive disproportionately less critical attention. Therefore, unlike meat, very little is known about the psychology of egg and dairy consumption. This study looks at vegetarians to address this gap, because they are more likely to show empathetic concern for animals than meat-eaters, yet actively choose to include these products in their diet, a conflict ripe for exploration. Interview data were analysed via thematic analysis, finding that vegetarians perceive robust ethical issues with NMAPs but give various justifications pertaining to personal benefits and social norms. Cognitive dissonance was evident and participants used various strategies to resolve it. This paper expands research on food psychology and animal ethics and may also be used to inform NMAP reduction strategies, an important pursuit in the quest for a more sustainable and compassionate world.

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.

Welfare of ducks, geese and quail on farm

This Scientific Opinion concerns the welfare of Domestic ducks (Anas platyrhynchos domesticus), Muscovy ducks (Cairina moschata domesticus) and their hybrids (Mule ducks), Domestic geese (Anser anser f. domesticus) and Japanese quail (Coturnix japonica) in relation to the rearing of breeders, birds for meat, Muscovy and Mule ducks and Domestic geese for foie gras and layer Japanese quail for egg production. The most common husbandry systems (HSs) in the European Union are described for each animal species and category. The following welfare consequences are described and assessed for each species: restriction of movement, injuries (bone lesions including fractures and dislocations, soft tissue lesions and integument damage and locomotory disorders including lameness), group stress, inability to perform comfort behaviour, inability to perform exploratory or foraging behaviour and inability to express maternal behaviour (related to prelaying and nesting behaviours). Animal-based measures relevant for the assessment of these welfare consequences were identified and described. The relevant hazards leading to the welfare consequences in the different HSs were identified. Specific factors such as space allowance (including minimum enclosure area and height) per bird, group size, floor quality, characteristics of nesting facilities and enrichment provided (including access to water to fulfil biological needs) were assessed in relation to the welfare consequences and, recommendations on how to prevent the welfare consequences were provided in a quantitative or qualitative way.

Fear, anxiety, and production in laying hens with healed keel bone fractures

For laying hens, the immediate aftermath and healing period of a keel fracture (KF) is characterized by reduced ability to perform species-specific behavior, access resources, and pain. However, the longer-term impacts, once the fracture is completely healed, are less clear. As well as acute pain and behavioral changes, a negative experience can shape future responses to putatively threatening stimuli, raising future fear, and anxiety levels during husbandry-related events. We aimed to determine whether hens that had previously sustained keel bone fractures, but were now outside of the peak age range for new fractures, showed higher fear and anxiety levels compared to intact hens. We also determined if healed keel bone fractures were associated with reduced production, changes in behavior and resource use. One hundred and fifty hens with a palpation score of 1 ( "KF") and 150 hens with a palpation score of 0 (keel fracture free, "KFF") were selected from a commercial farm at 63 wk of age and housed in 6 groups (3 × KF and 3 × KFF). We compared production (hen weight and feed consumption, egg quantity, quality and weight, floor eggs, shell thickness, and weight) and home pen behavior (behaviors and transitional movements) in both groups. Finally, we measured the responses of KF (n = 75) and KFF (n = 75) during tonic immobility, novel arena, and novel object tests. KF and KFF hens did not differ in their responses to the tonic immobility, novel arena, and novel object tests, nor were there differences between the 2 groups in home pen behavior and transitional movements. KFF birds were lighter and laid eggs with less eggshell membrane compared KF birds, but no differences were found between KF and KFF in any other production measures. We found no evidence that healed KFs were associated with detrimental welfare effects in laying hens, but further work is required to determine the mechanisms and implications of the lower body weight and egg shell membrane.

Keel bone fractures in broiler breeders: is palpation a reliable diagnostic method?

The aim of this study was to estimate the sensitivity and specificity of palpation relative to necropsy for detection of keel bone fractures (KBF) in broiler breeders. In addition, the study investigated observer reliability of palpation. Four commercial breeder flocks (Ross 308 n = 2, Ranger Gold n = 1, Hubbard JA 757, n = 1) were included in the study. A total of 400 hens and 60 roosters were examined after culling or slaughter, at end of lay (63 weeks). Keel bones were first palpated independently by two raters with a varying degree of experience in palpation of keel bones in laying hens. After palpation, a necropsy with investigation of the keel bone was conducted. The prevalence of KBF at end of lay for hens, as diagnosed by necropsy, varied from 14-58%, while only one in 60 assessed roosters had KBF. Palpation had poor sensitivity, with differences between raters ranging from 56% to 36% when hybrid is not considered. The specificity of palpation for all hybrids together was 85% and 88%, for the two raters, respectively. The two raters had moderate agreement, Gwet's agreement coefficient (95% confidence interval): 0.60 (0.52-0.69). In conclusion, palpation has poor diagnostic accuracy for detection of KBF in broiler breeders, and other methods, like necropsy, must be applied for reliable assessments. KBF appears to be a prevalent condition in different hybrids of broiler breeder hens, but not in roosters.RESEARCH HIGHLIGHTS This is the first study to investigate palpation as a diagnostic method for detection of KBF in broiler breeders.Palpation has poor diagnostic accuracy for detection of KBF in broiler breeder hens with differences between raters.KBF can be a prevalent problem in broiler breeder hens of several hybrids, but not in roosters.

End of lay postmortem findings in aviary housed laying hens

Good health and low mortality are constitutive elements of good animal welfare. In laying hens, mortality and pathological findings are usually reported as cumulative proportions from onset of lay to culling. However, knowledge of pathological lesions and causes of death specifically toward the end of the production period are scarce. This study aimed to investigate the occurrence of postmortem lesions and tentative causes of death in non-beak trimmed, end of lay hens, housed in multitiered aviary systems. A convenience sample of 48 flocks was recruited. In each flock, layers dead between wk 65 and 70 were necropsied in the field. In total, 482 layers were subjected to postmortem examination. The 4 most common pathological lesions were keel bone fracture (KBF) (92%), fatty liver (42%), emaciation (23%), and salpingitis (22%). Apart from keel bone fracture, the relative frequency of the pathological lesions variated between flocks, indicating that flock is an important factor. Common tentative causes of death were salpingitis (18%) and fatty liver hemorrhagic syndrome (FLHS) (13%). This study sheds light on health challenges aviary housed layers are facing end of lay, which is crucial knowledge in the development of preventive measures to secure good health and welfare.

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 &lt; ICC &lt; 0.987 (F49,268 = 54.2, p &lt; 0.0001). Intraclass correlation coefficient for intra-observer reliability was 0.831 with a confidence interval of 0.727 &lt; ICC &lt; 0.898 (F54,55 = 10.8, p &lt; 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 (sroh= 0.803, p &lt; 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.

Productive performance, perching behavior, keel bone and other health aspects in dual-purpose compared to conventional laying hens

Several alternatives to avoid killing male day-old chicks are available. One of these alternatives is to keep dual-purpose chicken strains. The aim of this study was to compare dual-purpose hens (Lohmann Dual, LD) with conventional laying hens (Lohmann Tradition, LT) in terms of performance, animal welfare parameters such as keel bone state and foot pad dermatitis, and perching behavior. We expected a generally equal or even better performance of the dual-purpose hens except for laying performance. Four hundred female day-old chicks were housed in 6 pens (3 pens per strain) and reared until 54 wk of age. Each pen offered a littered area, elevated slatted manure pit, elevated wooden frame with perches or grids and nest boxes on the manure pit. The wooden frame was alternately equipped with perches or grids. The elevated manure pit as well as the elevated structure was accessible via ramp. Productive performance parameters like mortality, total number of eggs and body weight were assessed periodically. In week 49, 132 hens (66 hens per strain) were randomly selected for radiography of the keel bone and assessment of plumage and foot pad state. Perching behavior was analyzed via scan sampling during rearing and laying period, respectively. Statistical analyzes were done with Linear Mixed Effect Model and General Linear Mixed Model. LD had a higher radiographic density than LT hens (P = 0.0016), other keel bone parameters (fracture score, P = 0.36; deformation, P = 0.83) showed no differences. The vast majority of fractures occurring in both strains were located in the caudal part of the keel bone. During the laying period, usage of elevated structures was higher with grids compared to perches (P < 0.001) and in LD compared to LT (P = 0.01). Some animal welfare problems were less frequent in LD compared to LT hens while other problems did not differ between the 2 strains or were even more frequent in LD hens. Grids may be more suitable as resting area than perches and may possibly help to decrease the prevalence of keel bone damage.

Bird Welfare in Zoos and Aquariums: General Insights across Industries

Animal welfare is a priority across accredited zoological institutions; however, historically, research has been prioritized for mammals. Bird-focused studies accounted for less than 10% of welfare research in zoos and aquariums over the last ten years. Due to the lack of scientific publications on bird welfare, zoo scientists and animal practitioners can look to other industries such as agriculture, laboratories, and companion animal research for insight. This qualitative review highlights findings across industries to inform animal care staff and scientists on the welfare needs of birds within zoos and aquariums. Specifically, the review includes an overview of research on different topics and a summary of key findings across nine resources that affect bird welfare. We also highlight areas where additional research is necessary. Future welfare research in zoos and aquariums should prioritize studies that consider a diversity of bird species across topics and work to identify animal-based measures with empirical evidence. Moving forward, research from other industries can help develop innovative research on bird welfare within zoos and aquariums.

The Relationships between Damaging Behaviours and Health in Laying Hens

Simple Summary

The design of housing systems and genetic selection of laying hens have in the past focused mainly on productivity, excluding issues around the animals’ behavioural needs and welfare. Because of inadequate housing conditions and especially a barren environment, behavioural disorders such as feather and body pecking, as well as cannibalism, occur in the modern layer industry. Since conventional cages for egg production were banned in the European Union in January 2012, alternative systems such as floor, aviary, free-range, and organic systems have become increasingly common and now concern over 50% of hens housed in Europe. Despite the many advantages that come with non-cage systems, the shift to a housing system where laying hens are kept in larger groups and more complex environments has given rise to new challenges related to management, health, and welfare. We have carried out a review showing the close relationships between damaging behaviours and health in modern husbandry systems for laying hens.

Abstract

Since the ban in January 2012 of conventional cages for egg production in the European Union (Council Directive 1999/74/EC), alternative systems such as floor, aviary, free-range, and organic systems have become increasingly common, reaching 50% of housing for hens in 2019. Despite the many advantages associated with non-cage systems, the shift to a housing system where laying hens are kept in larger groups and more complex environments has given rise to new challenges related to management, health, and welfare. This review examines the close relationships between damaging behaviours and health in modern husbandry systems for laying hens. These new housing conditions increase social interactions between animals. In cases of suboptimal rearing and/or housing and management conditions, damaging behaviour or infectious diseases are likely to spread to the whole flock. Additionally, health issues, and therefore stimulation of the immune system, may lead to the development of damaging behaviours, which in turn may result in impaired body conditions, leading to health and welfare issues. This raises the need to monitor both behaviour and health of laying hens in order to intervene as quickly as possible to preserve both the welfare and health of the animals.

In Pursuit of a Better Broiler: Welfare and Productivity of Slower-growing Broiler Breeders during Lay

Current commercial strains of broiler breeders display reproductive dysregulation when fed to satiety, but they can achieve optimal hatching egg production under feed restriction. However, chronic feed restriction in broiler breeders is a welfare concern due to physiological and behavioral signs of hunger, lack of satiety, and frustrated feeding motivation. The purpose of this study was to assess the welfare and productivity of slower-growing broiler breeders during lay. A total of 336 broiler breeders from 5 strains of slower-growing broiler breeders (3 female strains: 100 hens per strain, and 2 male strains: 12 and 24 roosters per strain) were kept in 12 identical pens throughout lay, 4 pens per combination of roosters and hens: A hens with Y roosters, B hens with Y roosters, and C hens with X roosters. According to guidelines, strain B and C hens and X roosters were slower growing strains and strain A hens and Y roosters were intermediate growing strains. Egg production was recorded daily, and settable eggs laid at 30, 40, and 50 wk of age were incubated to hatch. Growth rate, feed and water intake, and welfare indicators (feeding motivation, behavior, and physical assessment: feather coverage, foot and leg health, and keel bone status) were recorded during lay. Additionally, a subsample of 5 hens per pen was dissected for anatomical analyses. Laying rate started and peaked earlier in B hens than in A hens and remained above 70% in both strains, yielding high cumulative egg production (>165 eggs/hen) until 53 wk of age. Until 50 wk of age, fertility and hatched of fertile was high in slower growing broiler breeders, on average, above 95 and 80%, respectively. Compared to A hens, B and C hens had better feather coverage, lower feeding motivation, and lower daily water and feed intake. Results of this study suggest that slower growing broiler breeders show reduced signs of poor welfare and improved productivity during lay although susceptibility to obesity-related problems on laying rate may be strain-specific.

Keel bone damage affects behavioral and physiological responses related to stress and fear in two strains of laying hens

Keel bone damage (KBD) is more prevalent in alternative laying hen housing systems than in conventional cages, and its incidence differs from strain to strain. However, the information of KBD in Lindian chickens, a native Chinese strain, is limited. To investigate the effect of KBD on fearfulness and physiological indicators of stress in Lindian chickens and commercial laying hens, a total of two hundred 25-wk-old chickens (100 Hy-line Brown and 100 Lindian chickens) were studied for 7 wk. The birds were housed in furnished cages with 10 birds per cage for each strain. At 32-wk of age, the birds in each strain were divided into normal (NK), deviated (DK), and fractured (FK) hens according to the keel bone status. Ten birds in each keel bone status per strain were subsequently selected to collect blood for the determination of stress and fear-related indicators, including corticosterone, serotonin, interleukin-1β, and interleukin-6, and measure fear responses, including novel object test (NOT), human approach test (HAT), and tonic immobility (TI) test. The results showed that egg production was lower and the incidence of keel bone fractures was higher in Lindian chickens than in Hy-line Brown hens (P < 0.05). Lindian chickens showed a significantly increased whole blood serotonin content, NOT-latency, HAT-score, and TI induction times (P < 0.05) and decreased serum interleukin-6 content and TI-duration (P < 0.05) compared with Hy-line Brown hens. Additionally, FK hens had significantly elevated whole blood corticosterone, serum interleukin-1β and interleukin-6 levels, TI-duration, and NOT-latency (P < 0.05), and a reduced whole blood serotonin content (P < 0.05) compared with NK and DK hens. Our results indicated that KBD affected stress and fear responses, and this impact was mainly reflected by FK hens compared with NK and DK hens. We suggest that keel bone fractures are the main factor impairing hen welfare. Besides, the incidence of keel bone fractures and stress and fear responses of Lindian chickens are more severe than Hy-line Brown laying hens, indicating that the strain type can affect the health and welfare of laying hens.

Genetic Parameter Estimation and Whole Sequencing Analysis of the Genetic Architecture of Chicken Keel Bending

Bone health is particularly important for high-yielding commercial layer chickens. The keel of poultry is an extension of the abdomen side of the sternum along the sagittal plane and is one of the most important bones. In this study, the keel phenotype of White Leghorns laying hen flocks showed significant individual differences. To clarify its genetic mechanism, we first estimated the heritability of keel bend (KB) in White Leghorn, recorded the production performance of the chicken flock, examined the blood biochemical indexes and bone quality in KB and keel normal (KN) chickens, and performed whole-genome pooled sequencing in KB and KN chickens. We then performed selection elimination analysis to determine the genomic regions that may affect the keel phenotypes. The results show that KB is a medium heritability trait. We found that cage height had a significant effect on the KB (p < 0.01). At 48 weeks, there were significant differences in the number of eggs, the number of normal eggs, and eggshell strength (p < 0.05). The content of parathyroid hormone was lower (p < 0.01) and that of calcitonin was higher (p < 0.01) in KB chickens than in KN chickens. The differences in bone mineral density, bone strength, and bone cortical thickness of the humerus and femur were extremely significant (p < 0.01), with all being lower in KB chickens than in KN chickens. In addition, the bones of KB chickens contained more fat organization. A total of 128 genes were identified in selective sweep regions. We identified 10 important candidate genes: ACP5, WNT1, NFIX, CNN1, CALR, FKBP11, TRAPPC5, MAP2K7, RELA, and ENSGALG00000047166. Among the significantly enriched Kyoto Encyclopedia of Genes and Genomes pathways found, we identifed two bone-related pathways, one involving “osteoclast differentiation” and the other the “MAPK signaling pathway.” These results may help us better understand the molecular mechanism of bone traits in chickens and other birds and provide new insights for the genetic breeding of chickens.

Production Performance, Egg Quality Characteristics, Fatty Acid Profile and Health Lipid Indices of Produced Eggs, Blood Biochemical Parameters and Welfare Indicators of Laying Hens Fed Dried Olive Pulp

This study aimed to evaluate the long-term dietary effects of dried olive pulp (OP) on production performance, fatty acid profile and health lipid indices and quality characteristics of produced eggs, health and welfare indicators of laying hens. It was carried out in a commercial poultry farm using 300 Isa Brown layers at 23 weeks of age. The hens were randomly and equally divided in six dietary groups CON, OP2, OP3, OP4, OP5 and OP6, according to the inclusion rate of OP in the ration (0%, 2%, 3%, 4%, 5% and 6%, respectively). OP feeding increased the percentage of polyunsaturated fatty acids (PUFA) in eggs, decreased that of saturated fatty acids (SFA) and improved the PUFA to SFA ratio and health lipid indices, as indicated by the decrease of AI and TI and the increase in the h/H ratio of produced eggs, in a dose-dependent way. OP-fed layers presented a lower percentage of broken eggshells compared to controls. No adverse effects on birds’ performance, egg quality traits, health and welfare parameters were observed but a positive impact on Keel Bone Damage (KBD) incidence and belly plumage damage was recorded. OP feeding at the rates of 5% and 6% seems to be beneficial in improving egg nutrition quality.

Comparison of Behavioral Time Budget and Welfare Indicators in Two Local Laying Hen Genotypes (Atak-S and Atabey) in a Free-Range System

Simple Summary

It is known that laying hens kept in cage systems without access to enrichment have more welfare and behavioral problems. Therefore, alternative systems for egg production have gained popularity, e.g., free-range and organic systems, as they improve the birds’ possibilities to perform important specific behavior and thereby increase the welfare conditions in commercial farms. This study aimed to compare of the behaviors and welfare of two layer genotypes used in Turkey, Atak-S (brown) and Atabey (white), in a free-range system from 19 to 72 weeks of age. We evaluated multiple welfare indicators, including behavioral time budget, fear level, plumage condition, keel bone damage, and other body lesions. The birds were scored at 24, 40, 56, and 72 weeks of age. The Atabey hens showed more preening, walking–standing, and resting behavior, and they had a longer duration of tonic immobility. The Atak-S hens tended to perform more feather pecking and explorative pecking, and they had more foot lesions, plumage damage, skin injuries, and keel bone damages. Current results can be beneficial for the choice of genotype to use in free-range systems.

Abstract

Free-range systems are considered to improve bird health and welfare, thereby satisfying consumer demands. Behavioral time budget, fear level and clinical welfare indicators were compared for two Turkish laying hen genotypes, Atak-S (brown) and Atabey (white), reared in a free-range system. A total of 420 laying hens (210 Atak-S, 210 Atabey) were studied between 19 and 72 weeks of age. Higher percentages of eating and drinking behavior, feather pecking, and explorative pecking were observed for Atak-S hens, whereas Atabey hens were preening, walking–standing, and resting more. The duration of tonic immobility was longer, and the number of inductions was lower in Atabey compared with Atak-S hens. Atabey hens had less keel bone damages and better plumage conditions on the breast, wing, and tail at 56 and 72 weeks of age than Atak-S hens. Footpad dermatitis was more common in Atabey hens at 40 weeks, whereas Atak-S hens had a higher prevalence of footpad dermatitis with moderate lesions at 72 weeks of age. These findings indicate that free-range Atak-S hens may be more prone to keel bone damage and development of feather pecking, but they showed less foot lesions and were less fearful.

Abnormal Bone Metabolism May Be a Primary Causative Factor of Keel Bone Fractures in Laying Hens

Simple Summary

Keel is an essential structural bone, providing anchorage for the attachment of large breast muscles in birds, allowing them to flap wings and provide proper ventilation for their lungs during flight. Previous studies reported that keel bone damage (especially fractures) negatively affects the welfare, health, production performance, eggshell quality, and mobility of laying hens contained in different housing systems. Furthermore, various factors affect keel bone damage, including nutrition, age, housing systems, and strains of laying hens. However, studies on the effects of abnormal bone metabolism and development on keel bone damage in laying hens are limited. Therefore, this study aimed to investigate the impacts of bone metabolism and development status on keel bone damage by determining the levels of serum bone turnover markers in laying hens. The results showed that laying hens with impaired keel bone had significantly altered levels of serum Ca and P metabolism-related and osteoblast and osteoclast activity-related markers compared to those in laying hens with normal keel bone. Thus, these results indicated that abnormal bone metabolism before keel bone damage reflected by varying levels of serum bone turnover markers might be a pivotal factor causing keel bone damage in laying hens. Our results also provide new insights into the occurrence of keel bone damage in laying hens.

Abstract

Keel bone damage negatively affects the welfare, production performance, egg quality, and mobility of laying hens. This study aimed to investigate whether abnormal bone metabolism causes keel bone damage in laying hens. Eighty Hy-line Brown laying hens were housed in eight furnished cages with 10 birds per cage and studied from 18 to 29 weeks of age (WOA). Accordingly, keel bone status was assessed at 18, 22, 25, and 29 WOA using the X-ray method, and the serum samples of laying hens with normal keel (NK), deviated keel (DK), and fractured keel (FK) that occurred at 29 WOA were collected across all the time-points. Subsequently, the serum samples were used to measure markers related to the metabolism of Ca and P and activities of osteoblast and osteoclast. The results showed that FK laying hens had lighter bodyweight than NK and DK birds throughout the trial (p < 0.05), while the keel bone length and weight were not different in NK, DK, and FK hens at 29 WOA (p > 0.05). Moreover, bone hematoxylin and eosin (H&E) staining and tartrate-resistant acid phosphatase (TRAP) staining indicated that damaged keel bone had evident pathological changes. In the FK hens, serum P level was reduced but serum 1,25-dihydroxy-vitamin D₃ (1,25-(OH)₂D₃) and 25-hydroxyvitamin D₃ (25-OHD₃) levels were elevated compared to NK hens (p < 0.05). Additionally, DK hens had higher levels of serum 1,25-(OH)₂D₃, parathyroid hormone (PTH) and calcitonin (CT), and lower level of serum 25-OHD₃ than the NK birds (p < 0.05). Furthermore, serum alkaline phosphatase (ALP), osteocalcin (OC), osteoprotegerin (OPG), TRAP, and corticosterone (CORT) levels were elevated in DK and FK hens compared to NK hens (p < 0.05). The levels of serum Ca, P, PTH, ALP, TRAP, OPG, OC, and CORT in laying hens fluctuated with the age of the birds. Generally, the results of this study indicate that keel bone damage, especially fractures, could be associated with abnormal bone metabolism in laying hens.

Integument, mortality, and skeletal strength in extended production cycles for laying hens - effects of genotype and dietary zinc source

1. This study on long-life layers, covering the period 20-100 weeks of age, investigated longitudinal effects on mortality, layer integument, and skeletal properties in Bovans White (BoW) and Lohmann Selected Leghorn Classic (LSL), with or without supplementation with dietary organic zinc (Zn).2. Two experiments, using 1440 layers in furnished small group cages (FC) and 1836 layers in a traditional floor housing system (Floor), were run in parallel. Each replicate consisted of five adjacent cages containing eight hens in each FC, or a pen with 102 layers in the Floor group.3. Mortality was recorded daily. Integument and keel bone condition were scored at 35, 55, 85, and 100 weeks of age on 20% of the layers. Tibial strength was recorded from 933 layers at 100 weeks. Statistical analyses were performed on replicate means, with four to five and nine replicates per combination of hybrid and diet in Floor and FC groups, respectively.4. Cumulative mortality was 9.6% and 16.3% in FC and Floor, respectively, and increased in the latter part of the production cycle, particularly in the Floor group.5. In FC, LSL had inferior feather cover, less keel bone deviation, and shorter claws than BoW. In Floor, LSL had superior feather cover, less severe vent wounds, more bumble foot, and cleaner plumage than BoW. In both production systems, claws grew longer and keel bone deviation became more severe with age.6. In FC, layers fed organic Zn had lower body weight and less keel bone deviation at 100 weeks of age.7. In conclusion, keel bone integrity, claw length, and mortality rate are potential threats to welfare in long-life layers. Feather pecking is a problem that needs addressing at an early stage in the production period. On the whole, organic Zn did not improve welfare conditions in long-life layers.

Low dietary phosphorus impairs keel bone health and quality in laying hens

1. Phosphorus (P) is a necessary nutrient for egg production and bone quality in poultry diets. To investigate the effects of low dietary available P (avP) on keel bone, 180 laying hens were fed either a control (C, 0.3% avP) or low phosphorus (LP, 0.15% avP) diet from 20-36 weeks of age (WOA). Each diet was replicated in six cages with 15 birds per cage. Keel samples were collected at 24, 28, 32, and 36 WOA to measure indicators.2. The incidence of keel bone damage in the LP group was higher than C group and increased with age throughout the experiment period. Keel bone length from laying hens in the LP group was shorter than C group (P < 0.05) at 32 and 36 WOA.3. The mRNA expression of receptor activator of nuclear factor kappa-B ligand (RANKL) and ratio of RANKL to osteoprotegerin (OPG) were upregulated (P < 0.05), and that of sclerostin and OPG was downregulated (P < 0.05) in the LP group in comparison to hens in the C group. Meanwhile, mRNA expression of the integrin-binding sialoprotein was increased at 24 and 28 WOA (P < 0.05), and decreased at 32 and 38 WOA (P < 0.05) in the LP group.4. Laying hens in LP group had increased trabecular separation and bone surface fraction (P < 0.05), decreased bone volume, bone volume fraction, trabecular number and thickness, and bone mineral density (P < 0.05) at 32 WOA. The LP-fed hens had increased K, Ti, Mn, Fe, Zn, Se, Sr and Pb bone concentrations (P < 0.05), and decreased P and TI bone concentrations (P < 0.05) at 36 WOA.5. Feeding hens a P-deficient diet with 0.15% avP and 3.37% Ca during the laying period impaired keel bone quality, which could be related to the osteoporosis.

Dietary Soybean Oil Supplementation Affects Keel Bone Characters and Daily Feed Intake but Not Egg Production and Quality in Laying Hens Housed in Furnished Cages

To evaluate dietary soybean oil supplementation on production performance, egg quality, and keel bone health in laying hens. Two hundred and four laying hens at 20 weeks of age (WOA) were distributed into 12 cages containing 17 birds each. Birds were either fed a commercial diet (control group, CON) or a diet supplemented with 3% of soybean oil (SO group). Experiments lasted 17 weeks. Body weight, daily feed intake, production performance and egg quality were measured at 25, 29, 33, and 37 WOA. Birds were subsequently assessed for keel bone status by palpation, and keel was excised to measure bone length, microstructure, bone mineral density (BMD), elements contents, and the expression of osteoprotegerin (OPG), receptor activator of nuclear factor kappa-B ligand (RANKL), collagen type II alpha 1 (COL2α1), periostin (POSTN), and sclerostin (SOST). The results showed that dietary SO supplementation did not affect production performance and egg quality (P > 0.05), but improved body weight of hens at 29 and 37 WOA (P < 0.05), and decreased daily feed intake at 33 and 37 WOA (P < 0.05). Incidence of keel bone damage (especially fracture) was higher in hens of SO group. Keel bone length in birds of SO group was significantly decreased compared to CON (P < 0.05). Keel bone of supplemented hens showed increased trabecular separation at 29 WOA and higher levels of V, Mn, Fe, Se, and Ba at 33 WOA (P < 0.05). Moreover, decreased BMD, trabecular number and thickness were observed in keel bone of laying hens receiving supplementation at 29 and 37 WOA (P < 0.05); decreased levels of Li, Ca, Hg, and TI at 33 WOA and trabecular thickness at 37 WOA (P < 0.05) were also identified. mRNA levels of SOST and RANKL and the ratio of RANKL/OPG mRNA levels were increased in birds fed a SO-supplemented diet (P < 0.05); COL2α1, OPG, and POSTN were downregulated at all sampling points (P < 0.05). Taken together, results indicate that feeding laying hens a diet supplemented with soybean oil can decrease daily feed intake and impair keel bone health but not influence production performance and egg quality.

Effect of different rearing system on eggs production, hatchability, and offspring quality in layer breeders

This study analyzed the influence of an aviary system, in comparison with battery cages, on rearing and reproduction of parent-stock (PS) laying-type chickens. ISA Brown PS chicks were reared for 16 wk in battery cages or in an aviary system. Chickens reared in cages were kept there throughout the rearing period, whereas those reared in the aviary were released after 7 wk. The remaining housing conditions were similar in cages and the aviary. Body weight (BW, g), feed intake (FI, g/birds/d), and mortality (%) of birds were monitored during rearing. After the rearing period, the chickens were transferred to 4 litter poultry houses: flock C (in cages) to poultry houses C1 and C2 (total: 2,076 cockerels and 20,450 pullets); flock A (in aviary) to poultry houses A1 and A2 (total: 1,542 cockerels and 16,962 pullets). During the period of reproduction (48 wk), egg production (%), hatching egg production (%), waste egg (%) and litter egg production (%), feed conversion ratio (FCR, g) and water intake (mL) per laid egg, hatching egg, and hatched chick, mortality (week/%), and BW at 17 wk and after reaching 50% laying performance were monitored. Furthermore, during incubation, fertilization rate (%), hatchability (%), and chick quality were recorded. The results showed that aviary rearing was associated with lower FI and higher mortality of chicks up to 16 wk of age. The following effects were also observed for aviary rearing during reproduction: the average egg and hatching egg production were higher, while waste and litter egg production were lower; FCR per laid egg, hatching egg, and the number of hatched chicks were poorer; and water intake for the production of 1 hatching egg and 1 hatched chick was lower. In the case of flocks A, higher mortality and BW at 17 wk of age were recorded for both sexes. They were characterized by higher relative egg fertilization, but lower hatchability due to the higher share of unhatched eggs. No influence of PS flock rearing system on chick quality was observed. The obtained results indicate that the aviary rearing system can be recommended for PS laying-type flocks. However, future research should consider the impact of a different diet having higher energy concentration on PS flocks reared in aviaries and develop methods for counteracting higher mortality in these systems. This is particularly significant for roosters because too few roosters in flock may contribute to lower egg fertilization and higher embryonic mortality.

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.

Alpha-Ketoglutarate: An Effective Feed Supplement in Improving Bone Metabolism and Muscle Quality of Laying Hens: A Preliminary Study

The aim of the experiment was to assess the effect of dietary alpha-ketoglutarate (AKG) supplementation on performance, serum hormonal indices, duodenum and jejunum histomorphometry, meat quality characteristics, bone quality traits and cartilage degradation in laying hens with a mature skeletal system. Forty-eight 30 week-old Bovans Brown laying hens were randomly assigned to a control group or the group fed the basal diet plus 1.0% AKG. The experimental trial lasted 30 weeks. The supplementation of AKG increases blood serum content of leptin, ghrelin, bone alkaline phosphatate and receptor activator of nuclear factor kappa-Β ligand, while osteoprotegerin and osteocalcin decrease. While dietary AKG was given to laying hens negatively influenced villus length, crypt depth, villus/crypt ratio and absorptive surface area in duodenum and jejunum, these changes have no effect on feed intake, weight gain, nor laying performance. In breast muscles, no significant changes in skeletal muscle fatty acid composition were observed, however, a higher shear force and decreased cholesterol content following AKG supplementation were noted, showing the improvement of muscle quality. While dietary AKG supplementation did not affect the general geometric and mechanical properties of the tibia, it increased collagen synthesis and enhanced immature collagen content. In medullary bone, an increase of bone volume fraction, trabecular thickness, fractal dimension and decrease of trabecular space were observed in AKG supplemented group. The trabeculae in bone metaphysis were also significantly thicker after AKG supplementation. AKG promoted fibrillogenesis in articular cartilage, as indicated by increased cartilage oligomeric matrix protein immunoexpression. By improving the structure and maintaining the proper bone turnover rate of highly reactive and metabolically active medullar and trabecular bones AKG showed its anti-osteoporotic action in laying hens.

Psychological and Physiological Stress in Hens With Bone Damage

Abnormalities in bone development in humans and non-humans can lead to impaired physical and psychological health; however, evidence is lacking regarding the role of individual psychosocial factors in the development of poor bone conditions. Addressing this lack of knowledge, we used low-productive laying hens (n = 93) and assessed behavioral responses to an open-field test [at 17, 18, 29, 33 weeks of age (wa)], an aerial predator test (at 39 wa), and a social reinstatement test (at 42 wa). Bone condition was assessed using a palpation technique on five occasions (at 16, 29, 33, 45, 58 wa), with half of the hens experiencing damage (deviations, fractures, or both) at 29 wa and all hens by 58 wa. Corticosterone (CORT) concentration in feathers (at 16, 33, 58 wa) and body weight (at 23, 47, 58 wa) were also investigated. We hypothesized that lighter birds (at 23 wa) with higher CORT (at 16 wa) and open field-induced fear collected before the onset of lay (at 17 and 18 wa) are associated with a worse bone condition when in lay. We also hypothesized that those birds with more damage at the peak of laying (at 29 wa) would be lighter at 47 and 58 wa and more fearful by showing higher open field-induced (at 29 and 33 wa) and predator-induced fear responses, however, acting less socially toward conspecifics. These hens were also expected to have higher CORT (at 33 and 58 wa). Our results show no association between open-field fear level and fear behavior, CORT concentration, or body weight on the one hand (all measured before starting to lay) and bone damage at 29 wa on the other. When in lay, bone damage was associated with more pecking and less crossing zones when faced with an open-field situation at 29 wa and improved sociality at 42 wa. This study provides the first evidence of a relationship of bone health with fear, sociality, and stress response. When in poor bone condition, our hens had enhanced psychological stress measured by fear behavior reactivity but not physiological stress measured as feather CORT concentration.

Effects of housing systems on keel bone damage and egg quality of laying ‎hens

The aim of this study was to investigate whether keel bone damage is prevalent in laying hens in Greece. The study was conducted in three industrial farms using different housing systems: (a) enriched cages, (b) floor system, and (c) free-range system. One hundred hens per housing system, randomly selected, were evaluated for keel bone damages with the method of palpation. Complementarily, thirty eggs from each farm were selected for the measurement of egg weight, shape index, shell cleanness, shell color, shell breaking force, shell thickness, shell weight, egg yolk color, albumen height, and Haugh unit. The presence of keel bone damage was evident in all housing systems with the significantly highest occurrence being observed in the free-range system (50.00%), followed by enriched cages (24.00%) and floor system (7.00%). Eggs from all three systems had significant differences in all estimated egg quality parameters apart from shell color and Haugh unit.

Why Do Hens Pile? Hypothesizing the Causes and Consequences

Piling is a behavior in laying hens whereby individuals aggregate in larger densities than would be normally expected. When piling behavior leads to mortalities it is known as smothering and its frequent but unpredictable occurrence is a major concern for many egg producers. There are generally considered to be three types of piling: panic, nest box and recurring piling. Whilst nest box and panic piling have apparent triggers, recurring piling does not, making it an enigmatic and ethologically intriguing behavior. The repetitive nature of recurring piling may result in a higher incidence of smothering and could have unconsidered, sub-lethal consequences. Here, we consider the possible causes of recurring piling from an ethological perspective and outline the potential welfare and production consequences. Drawing on a wide range of literature, we consider different timescales of causes from immediate triggers to ontogeny and domestication processes, and finally consider the evolution of collective behavior. By considering different timescales of influence, we built four hypotheses relevant to the causes of piling, which state that the behavior: (i) is caused by hens moving toward or away from an attractant/repellent; (ii) is socially influenced; (iii) is influenced by early life experiences and; (iv) can be described as a maladaptive collective behavior. We further propose that the following could be welfare consequences of piling behavior: Heat stress, physical injury (such as keel bone damage), and behavioral and physiological stress effects. Production consequences include direct and indirect mortality (smothering and knock-on effects of piling, respectively), potential negative impacts on egg quality and on worker welfare. In future studies the causes of piling and smothering should be considered according to the different timescales on which causes might occur. Here, both epidemiological and modeling approaches could support further study of piling behavior, where empirical studies can be challenging.

Husbandry Conditions and Welfare Outcomes in Organic Egg Production in Eight European Countries

In the European research project HealthyHens, welfare indicators as well as husbandry and management conditions were recorded in 107 organic laying hen farms in eight countries. Farms were visited at peak and end of lay. Egg production was on average comparable to breeder specifications. A mean mortality of 5.7% and mean prevalences of footpad lesions of 30.5%, keel bone damage of 44.5%, 57.3% of flocks with on average >200 Ascarid eggs per gram faeces and 28.2% of flocks with >100 mites/trap were recorded. A large variation between flocks indicated options for improvement. Based on the results, the following measures can be recommended: (i) decreasing mite and worm infestation and (ii) providing an attractive covered veranda, because of their association with decreased mortality; (iii) maximising access to the free range, because of its relation to decreased A. galli infection and less injurious pecking; (iv) feeding sufficient protein levels and (v) providing adequate litter as preventive measure against feather pecking and cannibalism; (vi) ensuring that the birds have sufficient weight and (vii) preventing accidents by adequate hen house facilities and light conditions to reduce keel bone damage. These primarily management-based measures have the potential to improve bird welfare both in terms of behavioural and health aspects.

Prevalence of Keel Bone Damage in Red Jungle Fowls (Gallus gallus)-A Pilot Study

Keel bone damage (KBD) is a highly prevalent problem in commercial egg production. KBD consists of two different conditions affecting the keel: Keel bone deviation and keel bone fractures (KBF). Deviations are linked to pressure on the keel, e.g., from perching. The causative factors for KBF are not clear; however, selection for efficient egg production has been suggested as a major contributing factor. An important step to shed light on the role of selective breeding as an underlying cause of KBF in modern laying hens is to evaluate the keel bones of the ancestor, the red jungle fowl. To the authors' knowledge, this has never previously been published. The aim of this study was therefore to describe the prevalence of KBD in a study group of red jungle hens and roosters housed in an aviary system. The present study examined 29 red jungle fowls 112 weeks of age post-mortem; 12 hens and 17 roosters. Keel bones were evaluated by external palpation for deviations and fractures. Palpation was followed by autopsy. No fractures were detected in the 17 roosters; one had a very slight deviation. Of the 12 red jungle hens in this pilot study, one had a single fracture and 10 hens had a very slight deviation.

Bone Health or Performance? Adaptation Response of Genetically Divergent Chicken Layer Lines to a Nutritive Calcium Depletion

Simple Summary

Selection for high egg production in laying hens has led to an increased calcium requirement and consequently to an intensified calcium mobilization from the bones. However, excessive demineralization can lead to osteoporosis, which is manifested by a high incidence of bone-damaged hens. In this study, we characterized the adaptation response of laying hens to a repeated dietary calcium restriction (1.09% instead of 4.26% calcium) by means of egg production, eggshell quality, body weight and bone stability. The animal model included four layer lines differing in performance level (high vs. moderately performing lines) and phylogenetic origin (white-egg vs. brown-egg layers). We assumed that the high performing lines would respond by maintaining egg production level at the expense of eggshell quality and bone health. Egg production and eggshell quality declined considerably and bone demineralization occurred in all lines. Contrary to our hypothesis, there was evidence that phylogeny rather than performance level influenced the hens′ response. The brown-egg lines appeared to be more tolerant to the calcium depletion, while the white-egg lines were more sensitive. Our findings demonstrate the influence of genetics on the adaptive capacity of chickens and underline the importance of preserving genetic variability to cope with potential future environmental challenges.

Abstract

In modern laying hybrids, calcium (Ca) homeostasis is immensely challenged by daily eggshell calcification. However, excessive mobilization of Ca from bones may lead to osteoporosis, which then manifests in a high incidence of poor bone quality. The aim of this study was to characterize the hens’ adaptation response to an alternating dietary Ca restriction. The animal model consisted of four purebred layer lines, differing in laying performance (high vs. moderately performing lines) and phylogenetic origin (white- vs. brown-egg lines). According to the resource allocation theory, hens selected for high egg production were assumed to show a different response pattern to cope with this nutritive challenge compared to moderately performing lines. Data collected included egg number, egg quality traits, body weight and bone characteristics. The Ca depletion led to a temporary drop in egg production and shell quality and a loss of bone stability due to Ca mobilization. The white-egg lines response was more pronounced, whereas the brown-egg lines were less sensitive towards reduced Ca supply. Our study shows that the hens’ responsiveness to coping with a nutritive Ca depletion is not ultimately linked to genetic selection for increased egg production but rather to phylogenetic origin.

Severe calcification of systemic blood vessel walls caused by continuous hypercalcemia in a cat with congenital hypothyroidism

A 97-day-old male Japanese domestic cat was diagnosed as congenital hypothyroidism. During the treatment, continuous hypercalcemia was detected. Although fluid therapy was performed, the cat died at the age of 1785 days. At autopsy, both parathyroid glands were enlarged, and elastic arterial walls were increased in thickness and hardness. Histopathological examination revealed hyperplasia of both parathyroid glands and interstitial fibrosis of bilateral kidneys. Severe calcification of the tunica media and tunica externa in systemic elastic and muscular arteries were also observed. These calcifications were considered to be due to renal secondary hyperparathyroidism. In the present case, hypothyroidism might have caused hyperparathyroidism through renal failure. In veterinary medicine, this is the first reported case of hypothyroidism accompanied with hyperparathyroidism.

Hens with benefits: Can environmental enrichment make chickens more resilient to stress?

Resilience, the degree to which individuals are physiologically and behaviourally impacted by stressors, can be enhanced by positive experiences (e.g. positive moods in human, environmental enrichment in rodents). Such effects are important for human health, but could also have important animal welfare implications in terms of farm, laboratory and zoo animals' abilities to cope with stressors. Here we investigated whether enrichments can increase resilience in chickens, the world's most abundant agricultural animal. The stress reactivity of laying hens housed for 5-6 weeks in enriched environments was compared to that of controls housed in smaller, emptier, less preferred pens, via: 1) startle reflex amplitudes to an abrupt, intense sensory stimulus (a light flash); and 2) autonomic responses to restraint and the sudden appearance of a novel object, assessed from decreases in comb temperature. Startle amplitudes were consistently reduced in the enriched hens, exerted with around one sixth the force seen in control hens. Maximum comb temperature decreases, and latencies for comb temperatures to return to prestress levels, also both fell by around a third. Enrichment thus reduced hens' intrinsic behavioural and physiological responses to standardized stressors (doing so even outside the home pen), just as occurs in laboratory rodents. Enrichment also reduced baseline comb temperature, suggesting that this could be a non-invasive indicator of welfare. Altered judgment biases did not seem to be the mechanism. Further work should now investigate the processes underlying the apparently enhanced stress resilience of animals housed in preferred conditions, and also investigate baseline comb temperature as a chronic stress indicator in poultry.

Dietary supplementation of total flavonoids from Rhizoma Drynariae improves bone health in older caged laying hens

Caged layer osteoporosis (CLO) is a common bone metabolism diseases and poses a great threat to the production of laying hens. So far, there is no effective nutrition intervention to prevent CLO. The objective of this study was to evaluate the effects of dietary total flavonoids from Rhizoma Drynariae (TFRD), a Chinese herbal, on bone health, egg quality, and serum antioxidant capacity of caged laying hens. A total of two hundred sixteen, 54-wk-old Lohmann Pink-shell laying hens at were allocated to 3 groups with 6 replicates of 12 hens per replicate. The control group was fed a basal diet (BD) and 2 treatment groups additionally supplied with 0.5 or 2.0 g/kg TFRD, respectively. Results showed that supplying 2.0 g/kg TFRD enhanced the activities of serum total antioxidant capacity (P < 0.01) and glutathione peroxidase (P < 0.05) and had higher femur and tibia bone mineral density (both P < 0.05) compared with the control group. Dietary 2.0 g/kg TFRD also reduced the activities of serum alkaline phosphatase (P < 0.01), tartrate resistant acid phosphatase (P < 0.01), and the contents of osteocalcin (P < 0.01). Furthermore, tibia histomorphology observation showed that the microstructure of bone tissue was improved after TFRD treatment. Egg quality was not affected by TFRD while the egg weight significantly increased (P < 0.01). These findings suggested that TFRD has beneficial effects on bone health in older caged laying hens.

Welfare Assessment of Two Free-range Laying Hen Flocks in Turkey

This study aimed to determine the prevalence of keel bone deviations and feather damage of laying hens in two different free-range housing systems under commercial conditions. Both of the free-range systems had an indoor barn and an outdoor range area. The floor of the indoor barn consisted of litter and either perches (litter and perch, LP) or slats (litter and slats, LS). The hens of both flocks were raised under identical conditions in the same house during the rearing period and then divided and transferred to two different free-range housing systems for the laying period. Examinations were conducted on the flocks at the end of the production cycle. Hens from the LP group had a greater prevalence of keel bone deviation and feather damage compared to hens from the LS group. The highest percentage of severe feather damage was found in the back and tail body regions in both flocks. The findings of this study are based upon the evaluation of two Turkish laying flocks. Therefore further research with more replicates of these treatments is needed to reach a general conclusion.

Relationship between Bone Stability and Egg Production in Genetically Divergent Chicken Layer Lines

Impaired animal welfare due to skeletal disorders is likely one of the greatest issues currently facing the egg production industry. Reduced bone stability in laying hens is frequently attributed to long-term selection for increased egg production. The present study sought to analyse the relationship between bone stability traits and egg production. The study comprised four purebred layer lines, differing in their phylogenetic origin and performance level, providing extended insight into the phenotypic variability in bone characteristics in laying hens. Data collection included basic production parameters, bone morphometry, bone mineral density (BMD) and bone breaking strength (BBS) of the tibiotarsus and humerus. Using a multifactorial model and regression analyses, BMD proved to be of outstanding importance for bone stability. Only for the tibiotarsus were morphometric parameters and the bone weight associated with BBS. Within the chicken lines, no effect of total eggshell production on BBS or BMD could be detected, suggesting that a high egg yield itself is not necessarily a risk for poor bone health. Considering the complexity of osteoporosis, the estimated genetic parameters confirmed the importance of genetics in addressing the challenge of improving bone strength in layers.

Keel fracture changed the behavior and reduced the welfare, production performance, and egg quality in laying hens housed individually in furnished cages

Keel fracture has adverse effects on welfare, behavior, health, production performance, and egg quality of laying hens. To investigate this, 90 healthy Lohmann white laying hens with normal keel bones at 17 wk of age (WOA) were used in this study and housed individually in furnished cages. All hens were marked with fractured keel (FK) or normal keel (NK) based on the keel bone status through palpation at 5 time-points (22, 27, 32, 37, and 42 WOA). After the palpation, the behavior was observed for 2 consecutive days at each time-point, and the total number of eggs produced, dirty eggs, broken eggs, and feed intake of FK and NK laying hens were recorded at 27–32, 32–37, and 37–42 WOA, respectively. After each behavioral observation, 10 fresh FK hens and 10 NK hens were randomly selected to determinate the welfare and egg quality. The results showed that the incidences of keel fracture increased with the age of laying hens. Compared with NK hens, the sitting and standing behaviors significantly increased (P < 0.05) while feeding, walking, perching, and jumping behaviors significantly decreased (P < 0.05) in FK hens. There were no significant changes in drinking, preening, comforting, cage pecking, and nesting behaviors between NK and FK hens (P > 0.05). During the experiment period, the egg production rate, body weight, daily feed intake, and eggshell strength, thickness, and weight decreased (P < 0.05) and duration of tonic immobility increased (P < 0.05) in FK hens compared with those in NK hens. At 27–32 WOA, FK hens had significantly elevated broken egg rate (P < 0.05). There were no significant differences in the dirty egg rate, egg shape index, protein height, Haugh unit, feather cover score, and toe and foot pad health score (P > 0.05). Therefore, keel fracture in laying hens caused changes in behavior and reduced the welfare, production performance, feed intake, and eggshell quality.

Keel bone fractures induce a depressive-like state in laying hens

In commercial flocks of laying hens, keel bone fractures (KBFs) are prevalent and associated with behavioural indicators of pain. However, whether their impact is severe enough to induce a depressive-like state of chronic stress is unknown. As chronic stress downregulates adult hippocampal neurogenesis (AHN) in mammals and birds, we employ this measure as a neural biomarker of subjective welfare state. Radiographs obtained longitudinally from Lohmann Brown laying hens housed in a commercial multi-tier aviary were used to score the severity of naturally-occurring KBFs between the ages of 21-62 weeks. Individual birds' transitions between aviary zones were also recorded. Focal hens with severe KBFs at 3-4 weeks prior to sampling (n = 15) had lower densities of immature doublecortin-positive (DCX+) multipolar and bipolar neurons in the hippocampal formation than focal hens with minimal fractures (n = 9). KBF severity scores at this time also negatively predicted DCX+ cell numbers on an individual level, while hens that acquired fractures earlier in their lives had fewer DCX+ neurons in the caudal hippocampal formation. Activity levels 3-4 weeks prior to sampling were not associated with AHN. KBFs thus lead to a negative affective state lasting at least 3-4 weeks, and management steps to reduce their occurrence are likely to have significant welfare benefits.

Improving intra- and inter-observer repeatability and accuracy of keel bone assessment by training with radiographs

Assessing keel bone damage reliably and accurately is a requirement for all research on this topic. Most commonly, assessment is done on live birds by palpation and is therefore prone to bias. A 2-day Training School of the COST Action "Identifying causes and solutions of keel bone damage in laying hens" with 16 participants of variable experience was held where palpation of live hens was followed by consulting corresponding radiographic images of keel bones. We hypothesized that the inter-observer and intra-observer repeatabilities as well as the agreement between palpation and assessment from the radiograph (considered as the accuracy) would increase from day 1 to 2. Repeatability estimates were calculated using the R-package rptR and the change in level of accuracy on day 1 and 2 was analyzed with generalized linear models. As predicted, the inter-observer repeatabilities of the assessments of the fractures and deviations were improved by training, but this improvement differed for fractures and deviations between the cranial, middle, and caudal parts of the keel bone. Intra-observer repeatabilities before training also differed between the different parts of the keel bone and were highest for fractures at the caudal part of the keel bone. The training affected the accuracy of palpation to different degrees for the different parts of the keel bone. A training effect was found for the caudal part of the keel bone in regard to fractures and deviations, but for fractures the training effect was missing for the cranial part and for deviations it was missing for the middle part of the keel bone. In conclusion, the training school involving radiographs improved inter-observer repeatabilities in the diagnosis of fractures and deviations of keel bones and thus had the potential to lead to more comparable results among research groups.

Influence of later exposure to perches and nests on flock level distribution of hens in an aviary system during lay

Aviaries provide hens with many resources, but birds must develop motor and cognitive skills to use them properly. Introducing birds to aviaries at older ages has been reported to result in less use of perches, nests, and vertical space, which can reduce productivity and hen welfare. The objectives of this study were to examine (1) how enrichment influenced distribution of hens in the aviary during the day and (2) how enrichment influenced the distribution and roosting substrate of birds at night. Hy-Line W36 pullets were raised in floor pens before moving to laying aviaries (100 hens/aviary unit × 4 units/treatments). Control (CON) pullets were placed into aviaries at 17 wk of age (WOA). Floor (FLR) and enriched (ENR) pullets remained in floor pens until 25 WOA, and ENR birds were provided with perches and nests at 17 WOA. Birds were counted in tiers and litter areas of the aviary at morning, midday and evening at 36 and 54 WOA. Data were analyzed using generalized linear mixed models in R statistical software. At 36 WOA, ENR and CON birds occupied aviary areas at similar rates but differently from FLR birds. For example, in the morning 34% of CON hens and 30% of ENR hens occupied the highest tier compared to 15% of FLR hens (P < 0.01). At midday, 57% of CON and 57% of ENR birds were counted in litter compared with 77% of FLR birds (P < 0.01). In the evening, CON and ENR hens moved to the top tier of the aviary in greater numbers than FLR hens (22 and 17%, respectively, vs. 7%, P < 0.01). At 54 WOA, differences between FLR hens and CON/ENR hens were less pronounced, suggesting FLR hens were adapting to the aviary. Overall, we conclude that birds exposed to aviaries at 25 WOA can adapt to aviary systems, but take more time to do so than birds exposed to aviaries or vertical enrichment at 17 WOA.

The Reliability and Accuracy of Palpation, Radiography, and Sonography for the Detection of Keel Bone Damage

Simple Summary

Due to the recent increase in reports of the prevalence of keel bone damage in laying hens, this has become a topic of welfare concern. Keel bone damage is often in the form of a fracture, and therefore may compromise the hen’s welfare. Detecting keel bone damage in live hens has been problematic, as the bone must either be palpated, which is a measure poor in accuracy, or dissected, in which case the hen must be sacrificed. However, use of imaging technology is increasing in experimental studies. We set out to determine if training with feedback on accuracy could improve palpation accuracy, as well as to determine the accuracy of portable radiography and sonography to detect keel bone damage. Even with feedback, palpation remained an inaccurate method, while both radiography and sonography showed high accuracy for detecting fractures. These two techniques show promise in detecting keel bone fractures in live birds.

Abstract

Palpation is the most popular method of measuring keel bone damage on live birds, although it has been criticized for being subjective and inaccurate. The goals of this study were to examine intra- and inter-rater reliability when trained with feedback of accuracy, as well as determine the accuracy of portable radiography and sonography. Four evaluators palpated 50 103-week old Lohmann LSL-lite hens immediately following euthanasia. Of those birds, 34 were then radiographed, sonographed, and all 50 were re-palpated. Lastly, the keels were dissected and scored. The presence of deviations (DEV), fractures (FR), and tip fractures (TFR) was scored for each method. Reliability of palpation was analyzed using Cronbach’s Alpha (intra) and Fleiss’ Kappa (inter) tests. Radiography and Sonography scores were further compared with dissection scores to determine sensitivity and specificity. Initial inter-observer reliability was 0.39 DEV, 0.53 FR, and 0.12 TFR, with similar scores for the second round of palpation. Scores for intra-observer reliability ranged from 0.58–0.79 DEV, 0.66–0.90 FR, and 0.37–0.87 TFR. A high prevalence of TFR, but low assessor agreement, warrants the development of specialized training for the palpation of this area. Both radiography and sonography showed relatively high sensitivity for FR and TFR, but low for DEV. On the other hand, specificity was generally high across all damage types. Even with feedback, palpation reliability was poor. However, portable radiography and sonography show promise for detecting keel fractures.

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

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