Investigation of palpation as a method for determining the prevalence of keel and furculum damage in laying hens

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

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.

Impact of Perch Provision Timing on Activity and Musculoskeletal Health of Laying Hens

Laying hens can experience a progressive increase in bone fragility due to the ongoing mobilization of calcium from bones for eggshell formation. Over time, this escalates their susceptibility to bone fracture, which can reduce their mobility and cause pain. The provision of perches as an exercise opportunity could potentially enhance bone strength, but the timing of exposure to perches during the birds' development may modulate its impact. The objective of this study was to investigate the enduring impacts of perch provision timing on the musculoskeletal health of laying hens. A total of 812 pullets were kept in different housing conditions (seven pens/treatment, 29 birds/pen) with either continuous access to multi-tier perches from 0 to 40 weeks of age (CP), no access to perches (NP), early access to perches during the rearing phase from 0 to 17 weeks of age (EP), or solely during the laying phase from 17 to 40 weeks of age (LP). At weeks 24, 36, and 40 of age (n = 84 birds/week), three birds per pen were monitored for individual activity level, and blood samples were collected from a separate set of three birds per pen to analyze serum levels of tartrate-resistant acid phosphatase 5b (TRACP-5b) and C-terminal telopeptide of type I collagen (CTX-I) as markers of bone demineralization. At 40 weeks of age, three birds per pen (n = 84) were euthanized for computed tomography scans to obtain tibial bone mineral density (BMD) and cross-sectional area (CSA) with further analysis including muscle deposition, tibial breaking strength, and tibial ash percent. During week 24, hens from CP, EP, and LP pens had the highest overall activity compared to hens from NP pens (p < 0.05) with no differences between treatments for overall activity level during weeks 36 or 40 (p > 0.05). During weeks 24, 36, and 40, hens from CP and LP pens showed greater vertical and less horizontal activity compared to hens from EP and NP pens (p < 0.05). TRACP-5b and CTX-I concentrations did not differ between treatments at week 24 of age (p > 0.05). Hens from CP pens had the lowest TRACP-5b and CTX-I concentrations at 36 weeks of age with EP and LP hens showing intermediate responses and NP hens having the highest concentration (p < 0.05). At 40 weeks of age, CP hens had the lowest TRACP-5b and CTX-I concentrations compared to NP hens (p < 0.05). Total bone CSA did not differ between treatments (p > 0.05), but CP had greater total BMD than NP (p < 0.05) with no differences between EP and LP treatments. CP and LP hens had larger biceps brachii, pectoralis major, and leg muscle groups as well as greater tibial breaking strengths than EP and NP treatments (p < 0.05). CP hens had higher tibial ash percentages compared to EP, LP, and NP (p < 0.05). Our results indicate that providing continuous perch access improves the musculoskeletal health and activity of laying hens at 40 weeks of age compared to no access and that late access to perches has a beneficial impact on activity, muscle deposition, and bone strength.

Effect of restricted feeding on hen performance, egg quality and organ characteristics of individual laying hens

This study was to assess the impact of permanent or temporary restricted feeding on laying hen production traits, physiology, and egg quality. Two hundred and forty individually housed ISA Brown hens were monitored across 2 phases, assigned to 3 treatments: ad libitum feeding (ALF), temporary restricted feeding (TRF) and permanent restricted feeding (PRF), n = 80 hens per treatment. In Phase 1 (P1), 22 to 40 weeks, the TRF and PRF hens were offered 115 g of feed daily. In Phase 2 (P2), 41 to 46 weeks, the TRF hens were transitioned to ALF status while the ALF and PRF hens remained as in P1. From 35 to 40 weeks, eggs were collected once weekly from 15 hens per treatment and assessed for differences in albumen, yolk, and shell variables. At 45 weeks, 10 hens each from the ALF and PRF groups were euthanized and differences in organ characteristics were assessed. In P1, feed intake, feed to egg conversion ratio and body weight (BW) change were lower (P < 0.01), while albumen height and Haugh unit were higher (P < 0.01) in both PRF and TRF hen treatments compared to hens allocated the ALF treatment. In P2, TRF and ALF hens had a higher egg production and egg mass than PRF (P < 0.01) than ALF. Body weight change in P2 was higher in TRF and similar in both ALF and PRF, while feed intake and feed conversion ratio were higher in TRF followed by ALF and least in the PRF treatment group (P < 0.01). At 45 weeks ALF hens had a greater abdominal fat pad weight and fatty liver haemorrhagic syndrome lesion score compared to PRF. Restricting hens to 115 g of feed per day from point of lay restrained BW, improved feed conversion ratio and albumen quality and reduced abdominal fat pad deposition and clinical signs of fatty liver haemorrhagic syndrome in individually housed laying hens.

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.

Welfare of broilers on farm

This Scientific Opinion considers the welfare of domestic fowl (Gallus gallus) related to the production of meat (broilers) and includes the keeping of day-old chicks, broiler breeders, and broiler chickens. Currently used husbandry systems in the EU are described. Overall, 19 highly relevant welfare consequences (WCs) were identified based on severity, duration and frequency of occurrence: 'bone lesions', 'cold stress', 'gastro-enteric disorders', 'group stress', 'handling stress', 'heat stress', 'isolation stress', 'inability to perform comfort behaviour', 'inability to perform exploratory or foraging behaviour', 'inability to avoid unwanted sexual behaviour', 'locomotory disorders', 'prolonged hunger', 'prolonged thirst', 'predation stress', 'restriction of movement', 'resting problems', 'sensory under- and overstimulation', 'soft tissue and integument damage' and 'umbilical disorders'. These WCs and their animal-based measures (ABMs) that can identify them are described in detail. A variety of hazards related to the different husbandry systems were identified as well as ABMs for assessing the different WCs. Measures to prevent or correct the hazards and/or mitigate each of the WCs are listed. Recommendations are provided on quantitative or qualitative criteria to answer specific questions on the welfare of broilers and related to genetic selection, temperature, feed and water restriction, use of cages, light, air quality and mutilations in breeders such as beak trimming, de-toeing and comb dubbing. In addition, minimal requirements (e.g. stocking density, group size, nests, provision of litter, perches and platforms, drinkers and feeders, of covered veranda and outdoor range) for an enclosure for keeping broiler chickens (fast-growing, slower-growing and broiler breeders) are recommended. Finally, 'total mortality', 'wounds', 'carcass condemnation' and 'footpad dermatitis' are proposed as indicators for monitoring at slaughter the welfare of broilers on-farm.

Estradiol-17ß Is Influenced by Age, Housing System, and Laying Performance in Genetically Divergent Laying Hens (Gallus gallus f.d.)

The estrogen estradiol-17ß is known as one of the major gonadal steroid hormones with different functions in reproduction. In this study we analyzed estradiol-17ß concentration in laying hens of four pure bred chicken laying lines at four different time intervals of the laying period (17th-19th week of age, 33rd-35th week of age, 49th-51st week of age, and 72nd week of age). The high performing white egg (WLA) and brown egg (BLA) layer lines as well as the low performing white (R11) and brown (L68) layer lines were kept in both single cages and a floor housing system. We investigated whether there were differences in estradiol -17ß concentrations between lines at different ages that could be related to selection for high egg production or phylogenetic origin of the animals, and whether there was an influence of housing conditions on estradiol-17ß. Estradiol-17ß concentrations differed between high and low performing layer lines at all time intervals studied. High performing hens showed higher estradiol-17ß concentrations compared to low performing hens. In all lines, highest estradiol-17ß concentration was measured at their 49th to their 51st week of age, whereas the peak of laying intensity was observed at their 33rd to their 35th week of age. Additionally, hens with fewer opportunities for activity housed in cages showed higher estradiol-17ß concentrations than hens kept in a floor housing system with more movement possibilities. We could show that laying performance is strongly linked with estradiol -17ß concentration. This concentration changes during laying period and is also influenced by the housing system.

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.

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.

The Welfare Status of Hens in Different Housing Systems – A Review

The currently used poultry farming methods, which aim to maximise economic profit, are based on ever new technological solutions that improve flock management and increase bird performance. However, they do not always meet the natural needs of birds. Every housing method and technological solution currently in use is faced with some issues, such as social stress, adverse temperature/ humidity conditions, risk of zoonoses, and behavioural pathologies, which determine poultry performance and welfare. Disregard for animal welfare involves not only ethical but also practical aspects, because well-being and housing comfort translate into better weight gains, health and productivity of the birds. The studies reported here suggest that every production system, despite the many welfare-improving aspects, causes numerous behavioural, productivity and health abnormalities in laying hens. Therefore, further research is needed to identify various risk factors for the purpose of improving housing systems and increasing the welfare of hens.

Keel bone fractures in Danish laying hens: Prevalence and risk factors

Keel bone fractures (KBF) in commercial poultry production systems are a major welfare problem with possible economic consequences for the poultry industry. Recent investigations suggest that the overall situation may be worsening. Depending on the housing system, fracture prevalences exceeding 80% have been reported from different countries. No specific causes have yet been identified and this has consequently hampered risk factor identification. The objective of the current study was to investigate the prevalence of KBF in Danish layer hens and to identify risk factors in relation to KBF in all major productions systems, including parent stock production. For risk factor identification, production data from the included flocks was used. In total, 4794 birds from 40 flocks were investigated at end-of-lay. All birds were euthanized on farm and underwent inspection and palpation followed by necropsy. All observations were recorded and subsequently analysed using the SAS statistical software package. In flocks from non-caged systems, fracture prevalence in the range 53%-100%, was observed whereas the prevalence in flocks from enriched cages ranged between 50–98%. Furthermore, often multiple fractures (≥4) were observed in individual birds (range 5–81% of the birds with fractures) depending on the flock. The localization of the fractures at the distal end of the keel bone is highly consistent in all flocks (>96%). Macroscopically the fractures varied morphologically from an appearance with an almost total absence of callus, most frequently observed in caged birds, to large callus formations in and around the fracture lines, which was a typical finding in non-caged birds. Despite being housed under cage-free conditions, parent birds had significantly fewer fractures (all flocks were 60 weeks old) per bird, than other birds from cage-free systems. The body weight at end-of-lay had an effect on the risk of having fractures, heavy hens have significantly fewer fractures at end-of-lay. The older the hens were at onset of lay, the lower was the flock prevalence at end-of-lay. Additionally, the daily egg size at onset of lay was of importance for the risk of developing fractures, the production of heavier eggs initially, resulted in higher fracture prevalence at depopulation. The odds ratio of body weight, (+100 g) was 0.97, age at onset of lay (+1 week) was 0.87 and daily egg weight at onset (+1 gram) was 1.03. In conclusion, the study demonstrated a very high prevalence of KBF in hens from all production systems and identified hen size, age at onset of lay and daily egg weight at onset of lay to be major risk factors for development of KBF in the modern laying hen. Further research regarding this is warranted to strengthen the longevity and enhance the welfare of laying hens.

Rearing experience with ramps improves specific learning and behaviour and welfare on a commercial laying farm

To access resources in commercial laying houses hens must move between levels with agility to avoid injury. This study considered whether providing ramps during rear improved the ability of birds to transition between levels. Twelve commercial flocks (2000 birds/flock) on a multi-age site were examined between 1 and 40 weeks of age. All birds had access to elevated perching structures from 4 days of age. Six treatment flocks were also provided with ramps during rear to facilitate access to these structures. Flocks were visited three times during rear and three times at lay to record transitioning behaviour and use of the elevated structures, together with scores for keel bone and feather damage. Ramp reared flocks used the elevated structures to a greater extent at rear (P = 0.001) and at lay, when all flocks had ramps, showed less hesitancy [i.e. pacing (P = 0.002), crouching (P = 0.001) and wing-flapping (P = 0.001)] in accessing levels. Mean levels of keel bone damage were reduced in ramp reared flocks (52%) compared with control flocks (64.8%) at 40 weeks of age (P = 0.028). The early life experience of the ramp reared flocks enabled specific learning that translated and persisted in later life and resulted in overall welfare benefits.

Dietary betaine reduces plasma homocysteine concentrations and improves bone strength in laying hens

1. This study tested the hypothesis that the methyl-donor properties of betaine could reduce homocysteine concentrations, which has been recognised in a previous genetics study to be linked to bone quality. This was combined with phytase treatment, as phosphorus is critical for bone mineralisation.2. Using a 2 × 2 factorial arrangement, a total of 1920 Lohmann LSL-lite chickens housed as 24 replicates of 20 chickens were fed one of four diets containing dietary betaine (0 or 1000 mg/kg) and phytase (300 or 1000 FTU/kg) from one day old until end-of-lay. Blood and bone samples were collected at 45 and 70 weeks of age.3. Hens fed betaine had lower plasma homocysteine level (P < 0.05), higher tibia breaking strength (P < 0.05) and higher tibia bone density (P < 0.05).4. Egg production and quality was excellent throughout the study and were not affected by the dietary treatments.5. The addition of dietary betaine was successful at reducing plasma homocysteine concentrations and improving bone strength in laying hens, which could be used as an intervention to alleviate welfare concerns.

Advances in genetic selection and breeder practice improve commercial layer hen welfare

Modern commercial layer breeds represent the culmination of ~7000 years of natural genetic selection. This selection was driven in former times by a combination of genetic-shift and -drift events, that led to chickens being favoured as domesticated species for meat and egg production. More recently, in the early 20th century, the concept of hybrid vigour was discovered and accelerated the natural breeding progress that delivered new genetic lines and more favourable production traits. In the mid-20th century, the broiler-type and egg layer-type lines diverged and, in the 21st century, genetic analysis has further accelerated the progress made towards extended primary breeding characteristics such as egg quality, production and feed-intake traits, together with secondary breeding characteristics such as behavioural traits that have improved robustness in different housing systems, climates and feed types, which together have significantly improved welfare traits. Most recently, there has been the adoption of higher-powered computational analytics together with quantitative trait loci and single-nucleotide polymorphism assessment, which have further improved the uniformity of production traits within breeds. Most importantly, this has provided the primary breeding companies with improved and broader basis of selection of the modern commercial layer breeds, which also improved the alignment of layer strains with market requirements, and diverse variations in housing, nutritional and environmental conditions. This is also testament to the speed with which the commercial layer geneticists can respond to changing welfare policy on factors such as stocking density and beak treatment. The present paper reviews the modern approaches to genetic selection, including considerations of and benefits to the welfare state of commercial layers.

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.

A Descriptive Study of Keel Bone Fractures in Hens and Roosters from Four Non-Commercial Laying Breeds Housed in Furnished Cages

The presence of keel bone fractures (KBF) in laying hens has been documented and discussed by several authors, nevertheless the causative factors behind KBF remain uncertain. High prevalence of KBF have been reported in all commercial egg production systems, in different genetic lines and at different ages. Several of the proposed causal mechanisms behind KBF are linked to selection for efficient production. It is, therefore, of interest to explore whether less selected breeds have a lower occurrence of keel bone fractures compared to reports from highly selected, modern laying hen breeds. Thus, the aim of the current study was to investigate keel bones of hens from four non-commercial layer breeds. Birds were housed in furnished cages and keel bones examined at 30 and 63 weeks of age, using a portable X-ray equipment. The results from this descriptive study indicate a low prevalence of KBF at both ages in all four breeds, with only five KBF detected in 213 X-ray pictures taken from 126 birds. Of these, four of the KBF were observed in the most genetically selected breed, with an early onset of lay. None of the roosters examined exhibited KBF. The overall low numbers of KBF found indicate that genetic factors may be involved in KBF and, thus that selective breeding may help to reduce the susceptibility to KBF. Finally, this study highlights the importance of poultry conservation to secure genetic diversity, which may be an important resource in future selection schemes.

Effects of cage type on performance, welfare, and microbiological properties of laying hens during the molting period and the second production cycle

As most of the unenriched cages will soon switch to enriched cages, it is important to characterize all the effects in the laying hens for sustainable production. Laying hens can be used in several production periods by applying molting. The aim of this study was to determine the cage type (unenriched and enriched) on performance, welfare, and microbiological properties of laying hens during the molting period and the second production cycle. Overall, 840 brown laying hybrids were used in the experiment. Laying hens were reared on two different cage types (unenriched cage (UEC) and enriched cage (EC)) in the same poultry house. When the hybrids were 75 weeks old, they were subjected to force molting with whole grain barley. Performance, welfare, microbiological, and serological data of laying hens were obtained from 73 to 107 weeks of age. Egg production, egg weight, feed conversion ratio, breaking strength, albumen and yolk index, Haugh unit, feather condition, and breaking force of femur and metatarsus were better in the post-molting period. However, keel bone deformities and Newcastle disease virus antibody titers are the worst in the post-molting period. Stiffness of femur and metatarsus was increased with period. These results indicate that necessary precautions should be taken against the problems that may occur in the direction of bone and health. During the molting period, hens kept in EC had lower egg production but they returned to egg production at a high rate. EC type had a positive effect on egg production, feed conversion ratio, feather and foot condition, and breaking force of metatarsus.

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.

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

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

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.

Radiographic Evaluation of Keel Bone Damage in Laying Hens-Morphologic and Temporal Observations in a Longitudinal Study

The keel bone of commercially kept laying hens is known to be frequently affected by morphologic changes such as fractures and deformations with important implications for animal welfare. To detect morphologic changes, various methods such as palpation, computed tomography, and ultrasound are available, though radiography allows for the greatest level of detail in combination with the most ease of use. To explore the benefits of radiography in providing objective data on keel fractures from the age of 22–61 weeks within a single laying period, the keel bones of 75 Lohmann Brown and 75 Lohmann Selected Leghorns were radiographed every 3 to 5 weeks. Type, location, angulation, dislocation, callus formation, and healing process were assessed descriptively for each lesion. Ninety-nine percent of the animals showed at least one keel bone lesion during the study and 97% of the animals had at least one keel bone fracture. In 77% of the cases, the caudal third of the keel bone was affected. The fracture types were transverse and oblique (88%), comminuted, and butterfly. Further lesions were sclerosis, new bone formation and angulation. For each keel bone, an average of three fractures (3.09 ± 1.80) was detected at the end of the study. The described radiographic protocol for keel bone lesions was suitable for longitudinal, on-site examinations in conscious laying hens. Our results also indicate that keel bone fractures are more frequent than reported in earlier studies. The described radiographic examination protocol can be used to perform comparative studies of palpatory findings, or to assess the clinical significance of different fracture types which require a high level of detail.

Pathological characterization of keel bone fractures in laying hens does not support external trauma as the underlying cause

Keel bone fractures in laying hens have been described with increasing prevalence from several countries over the last twenty years and are considered one of the greatest welfare problems to the layer industry. In Denmark we have observed fracture prevalence in the range of 53% to 100% in flocks from cage-free systems whereas flock prevalences in birds from enriched cages ranged between 50-98%. Previous research have speculated that the underlying reason for the development of keel bone fractures is trauma in relation to impact of the bird with furniture, other equipment etc. However, little evidence of this theory has been provided. Predisposing factors have also been suggested including genetics of the bird, lack of specific feedstuff components, high egg production, management factors and layer fatigue. This study has addressed the possible pathogenesis of these fractures by pathological characterization of fractures in birds from different production systems. More than 60 keel bones with fractures have been characterized histo-pathologically and by CT scan. This included an assessment of damage to muscles and soft tissues, the bone and the healing process including callus formation. This investigation has shown that high energy collisions cannot be responsible for the majority of fractures, located at the caudal tip of the keel bone, observed in laying birds as markers associated trauma were not observed in the majority of the cases just as few recognized healing processes were observed. These results suggest an alternative pathogenesis to trauma.

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.

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.

Keel Fracture Causes Stress and Inflammatory Responses and Inhibits the Expression of the Orexin System in Laying Hens

Simple Summary

Keel fracture is an important health and welfare problem in laying hens in all production systems. Previous studies have shown that keel fracture can influence hens’ behavior, reduce production performances, and cause pain in laying hens. Additionally, keel fracture also affects their feed intake. However, it is not clear whether the keel fracture induces stress, inflammation, or influences the orexin systems in laying hens. Orexin, also called hypocretin, is associated with the regulation of feed intake, energy homeostasis, and metabolism in poultry animals. Therefore, this study aimed to investigate the effects of keel fracture on stress and inflammatory responses and the activity of the orexin system of laying hens. Our results indicate that keel fracture not only induced stress and inflammatory responses, but inhibited the activity of the orexin system in laying hens. This study provides insights into the adverse effects of keel fracture on laying hens.

Abstract

Keel fracture has negative effects on the health and welfare of laying hens. We investigated effects of keel fracture on stress, inflammation, and the orexin system in laying hens. Ninety 17-week-old Lohmann white laying hens were palpated and euthanatized at 42 weeks old, and marked as normal keel (NK)/fractured keel (FK) from absence/presence of keel fracture. Serum, brain, liver, and abdominal-muscle samples were collected from 10 NK and 10 FK hens to determine the stress and inflammatory responses and the activity of orexin systems by corticosterone content, expression of heat shock proteins (TNF-α 60, 70, 90), and inflammatory factors (tumor necrosis factor (TNF)-α, nuclear factor-kappa Bp65 (NF-κBp65), inducible nitric oxide synthase (iNOS), prostaglandin E synthases (PTGEs), cyclooxygenase-2 (COX-2), interleukin-1β (IL-1β)), orexin (ORX), and orexin-receptor 1/2 (ORXR1/ORXR2). The FK hens had higher serum corticosterone content, Hsps, and inflammatory factor mRNA expression levels than NK hens, although levels of iNOS in the liver and TNF-α in the muscle were similar. Protein levels of Hsp70 and Hsp90 in the brain and liver, iNOS and COX-2 in the liver, NF-κBp65, iNOS, and COX-2 in the brain of FK hens were increased compared with NK hens. Furthermore, FK hens had lower mRNA expression of ORX, ORXR1, and ORXR2 than NK hens. Therefore, keel fracture causes stress and inflammation, and inhibits the expression of the orexin system in laying hens.

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.

Keel bone damage assessment: consistency in enriched colony laying hens

Damage to the keel bone is a major issue in the laying hen industry. The goal of this study was to compare palpation results of live laying hens to digital computed tomography (CT) images, to assess changes in palpation reliability as training and familiarity increased, and to examine keel bone morphology over time. The longitudinal study consisted of 2 trials of 3 observation periods using 40 different (n = 120) W-36 hens housed in enriched colony cages. The first trial began when hens were 52 to 58 wk of age repeating the trial when the same birds were 74 to 81 wk of age. At 52 wk of age, each hen's keel bone was palpated by a single individual for keel bone caudal tip fractures (Tip), sagittal deviations (Evenness), and transverse deviations (Straightness). After palpation, each hen was placed in a motion limiting restraint and scanned using CT. The hens spent the next 21 d in their cages and on day 21, the hens were collected, palpated, and CT scanned again. The CT scans were imported into Mimics analysis software, 3D models of each keel bone were constructed and evaluated. Each bone and 3D model was scored (0, 1, 2) on the measurement of transverse deviation based on <0.5 cm, 0.51 to 1.0 cm, and >1.0 cm total deviation, respectively. Analysis of data using Proc Freq and Means in SAS 9.3 revealed minimal to moderate kappa values and moderate agreement percentages between palpators and digital analysis. The computer generated 3D models of individual keel bones were compared to palpation scores for Tip, Evenness, and Straightness at the beginning and end of each trial. The visual observations of the 3D models were qualitative, performed by a single individual. Overall, we found CT scanning to be a useful tool in observing changes to the keel bone, we observed changes in palpation accuracy as training/familiarity increased, and examined changes in keel morphology, specifically in the tip, after 52 wk of age.

Keel bone differences in laying hens housed in enriched colony cages

Keel bone damage may be painful to birds and affect their production. In order to better understand the frequency, position, and timepoint of keel bone damage that occur during production, the integrity of W-36 laying hen keel bones housed in enriched colony cages at 748.4 cm2 (116 in2) was evaluated. At four time points, 120 birds (10 per cage; three cages per each of four rooms) had keel bones evaluated. Each hen was placed in a motion limiting restraint, scanned using computed tomography (CT), fitted in vests containing tri-axial accelerometers, and placed back in their cages for 21 d. After 21 d, the hens were rescanned and returned to their cages. This process was repeated after 133 d. The CT scans were imported into Mimics analysis software (Materialise, Plymouth, MI, USA); 3D models were made of each keel bone at each time point and exported to 3-matic analysis software (Materialise, Plymouth, MI, USA). Each laying hen's keel bone model was superimposed onto scans from multiple time points resulting in four bone pairings representative of each 21-d period, the 133-d period, and the entire duration of the project. Next, the proximal portion of each bone pairing was edited to normalize bone shape according to a strict protocol. Additionally, each pairing was divided into three portions: distal aspect (3 cm), proximal aspect (2 cm), and middle portion (remaining). Whole bone pairing and each bone portion was analyzed using the Part Comparison tool in 3-matic. Raw data were compiled into three datasets and analyzed in SAS 9.3 using the GLIMMIX procedure using a three-level random intercept model. The model controlled for time, part, part(time), and system with random intercepts of bird(cage) and cage. Overall, results revealed that the greatest morphological changes occurred during the first 21-d period with regards to time (P = 0.03) and in the distal aspect of the keel with regards to part (P < 0.0001).

Assessing keel bone damage in laying hens by palpation: effects of assessor experience on accuracy, inter-rater agreement and intra-rater consistency

Accurate assessment is essential when evaluating keel bone damage. Palpation is commonly used to assess keel bone damage in living hens. However, there is little information on the accuracy of assessment of deviations and fractures on different parts of the keel, and on the consistency within, and agreement between, assessors. Crucially, although the importance of experience is commonly emphasized, knowledge on its effect is scarce. Ten assessors with or without prior experience palpated the same 50 75-wk-old hens for deviations, medial fractures, and caudal fractures (scored as present/absent). Accuracy, sensitivity, specificity, precision, and negative predictive value were determined by comparing palpation scores to post-dissection assessment, and then compared between experienced and inexperienced assessors. To determine the effect of the experience gained during the experiment, hens were subsequently re-assessed. Consistency within, and agreement between, assessors were also determined. Assessors with prior experience were more accurate (proportion of accurately assessed deviations: experienced 0.83 vs. inexperienced 0.79±0.01, P = 0.04; medial fractures: 0.82 vs. 0.68±0.03 in session 1 only, P = 0.04; caudal fractures: 0.41 vs. 0.29±0.03, P = 0.03), and inexperienced assessors classified medial fractures more accurately in session 2 (session 1: 0.68 vs. session 2: 0.77±0.04, P = 0.04). However, effect sizes were small for deviations and even experienced assessors lacked accuracy when assessing caudal fractures. Unexpectedly, deviations tended to be assessed more accurately in session 1 than in session 2, regardless of assessor status (1: 0.83 vs. 2: 0.79±0.01, P = 0.06), suggesting that prolonged assessment contributes to errors. Prior experience decreased specificity and precision of fracture assessment (more unfractured keels were classified as fractured) even though overall accuracy was greater. Intra-rater consistency was fair to good (0.55 to 0.67) for deviations and medial fractures, but poor to fair (0.36 to 0.44) for caudal fractures, and unaffected by prior experience (P = 0.49 to 0.89). In conclusion, experience improves accuracy to a limited extent but does not guarantee high accuracy for all types of damage. Future research should determine if other training methods (e.g., comparison to post-dissection scores or to radiographs) improve accuracy.

Free-range laying hens: using technology to show the dynamics and impact of hen movement

Free-range laying hens are provided with the opportunity to access various structural areas, including open floor space, feed areas, water lines, next boxes, perches, aviary tiers, winter gardens and ranges. Different individual location preferences can lead to the development of hen subpopulations that are characterised by various health, welfare and performance parameters. Understanding the complexity of hen movement and hen interactions within their environment provides an opportunity to limit the disadvantages that are associated with housing in loose husbandry systems and aids in decision-making. Monitoring hen movement using modern technologies such as radio-frequency identification (RFID), optical flow patterns, image analysis and three-dimensional (3D) cameras allows the accumulation of big data for data mining, clustering and machine learning. Integrating individual-based management systems into modern flock management will not only help improve the care of under-performing hens, but also ensure that elite hens are able to use their full genetic potential, allowing an ethical, sustainable and welfare friendly egg production. This review highlights the dynamics and impact of hen movement in free-range systems, reviews existing knowledge relevant for feeding hens in non-cage systems, and outlines recent technological advances and strategies to improve the management of free-range laying hens.

Limestone particle size fed to pullets influences subsequent bone integrity of hens

This study was conducted to evaluate limestone particle size (LPS) in 2 strains of laying hens housed in conventional cages or aviaries on bone integrity. Lohmann Brown and Bovan White pullet chicks were started in equal numbers on the floor or in battery brooders and were intermingled throughout all subsequent housing systems. At 5 wk of age, 432 floor-raised pullets were moved to 8 aviary cages. At 10 wk, 256 battery-raised pullets were transferred to 64 conventional layer cages. Pullets were given diets containing fine (LPS-FINE, 0.431 mm) or a blend of fine and coarse (LPS-BLEND, 0.879 mm) LPS from 7 to 17 weeks. Data were analyzed as a split plot factorial design with strain as subplot and with 4 replicates for each treatment combination. Body weight, feed intake, egg production, and eggshell breaking strength and percentage were measured. Tibia bone mineral density (BMD) was determined using a dual energy x-ray absorptiometry. Presence of keel indentations, curvatures, or fractures was recorded. LPS-BLEND increased BMD (0.215 vs. 0.208, P = 0.03) at 18 weeks. During the pullet phase, the odds of pullets fed LPS-FINE displaying keel curvatures were 2.8 times the odds of those fed LPS-BLEND (P = 0.04). At 54 wk, hens fed LPS-BLEND as pullets had lower odds of keel indentations (P = 0.02). Brown aviary hens fed LPS-BLEND as pullets had the lowest egg production compared to the rest of the treatment combinations (P = 0.004). Taken together, feeding LPS-BLEND to pullets improved bone mineralization at the onset of sexual maturity and reduced keel damage during the pullet and layer phases, regardless of strain; however, LPS-BLEND was associated with lower egg production in Brown hens housed in aviaries compared to all others.

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

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

Radiographic examination of keel bone damage in living laying hens of different strains kept in two housing systems

A high prevalence of deviations and fractures of the keel bone is a widespread welfare problem in laying hens. The aim of this study was to experimentally investigate this multifactorial problem throughout the laying period and to compare the prevalence and severity in different layer lines and different housing systems. High performing white (WLA) and brown (BLA) pure bred layer lines and low performing white (R11, G11) and brown layer lines (L68) were kept in both single cages and a floor housing system. A total of 97 hens (19 or 20 from each line, respectively) were repeatedly radiographed in the 35th, 51st and 72nd week of age. Fracture prevalence increased with age (p<0.001). The proportion of deviated keel bone area increased only for caged BLA, WLA and R11 hens (p<0.05) and was significantly higher for caged WLA and R11 hens compared to floor-housed WLA and R11 hens in the 72nd week of age (p<0.05). In the 72nd week of age hens in the floor housing system showed significantly more fractures than hens kept in cages (p<0.05). Prevalence of keel bone deviations was significantly higher in the white layer line R11 but significantly lower in the white layer line G11 compared to both brown layer lines and WLA (p<0.05). Brown layers showed significantly more fractures than white layers (p<0.05) in the 51st and 72nd week of age. Within the brown layers there was a significantly lower prevalence of deviations (p<0.05) and fractures (p<0.05) in the low performing (L68) compared to the high performing line (BLA). Our results show a different development of keel bone damage in caged compared to floor-housed hens under experimental conditions. Additionally, they indicate genetic effects on keel bone damage.

Influence of alternative husbandry systems on postmortem findings and prevalence of important bacteria and parasites in layers monitored from end of rearing until slaughter

In the present study 66 layer flocks housed in different alternative husbandry systems were monitored from placement of birds on the farm until slaughter to evaluate a possible influence on the occurrence of selected non-infectious as well as infectious diseases. Postmortems were performed and the occurrence of extraintestinal Escherichia coli and Gallibacterium anatis was investigated. No specific postmortem findings were seen in pullets. Non-infectious diseases were mainly found in layers. Most prominent postmortem findings in layers were reproductive tract lesions and the presence of intestinal helminths. From each flock E coli and from approximately 65 per centof the flocks G anatis were isolated. No significant differences were seen in regard to the housing system, but the prevalence of G anatis increased with the age of birds. The majority of reproductive tract lesions could be associated with E coli alone or G anatis co-infections. The prevalence of Ascaridia galli and Heterakis gallinarum was not influenced by the housing system, but significantly increased with age. Cestodes were present in six flocks. Histomonosis was detected twice. Dermanyssus gallinae was found in 5 pullet and 20 layer flocks. Additional investigations were performed on demand. Again, reproductive tract lesions were the most prominent postmortem findings. In one flock each histomonosis or erysipelas was diagnosed, respectively. Severe affection by D gallinae was found once. Necrotic enteritis was seen in two layer flocks.

The ability of laying pullets to negotiate two ramp designs as measured by bird preference and behaviour

BACKGROUND

Laying hens are often kept in barn or free-range systems where they must negotiate level changes in the house to access resources. However, collisions and resultant keel fractures are commonplace. Producers sometimes add ramps to make raised areas more accessible but designs vary and very little research has investigated bird preference or behaviour when using different ramp designs, or the effect of ramp design on falls and collisions.

METHODS

Two ramp designs were studied in an experimental setting-a ramp made of plastic poultry slats (grid ramp, GR) and a ramp made of wooden rungs (ladder ramp, LR). Sixty-four young female hens were trained to move to a food reward and this was used to test their behavioural responses when first negotiating the two different ramps during individual tests. Both upward and downward transitions were studied. Ramp preference was also tested using a room that replicated a commercial single-tier system with both types of ramp available. Birds were placed in this room in groups of 16 for three days and their use of the ramps studied.

RESULTS

A greater percentage of birds successfully completed (reached the reward bowl) on the GR than the LR during both upward (58% vs 37%) and downward (83% vs 73%) transitions, and a smaller percentage of birds made zero attempts to use the GR than the LR (upwards: 13% vs 56%, downwards: 8% vs 26%). When making a downward transition, more hesitation behaviours were seen (head orientations, stepping on the spot, moving away) for the LR. However, more head orientations were seen for the GR during the upward transition. Birds were more likely to abort attempts (an attempt began when a bird placed both feet on the ramp) to move up the GR than the LR. Birds took longer to negotiate the LR than the GR in both directions, and more pauses were seen during a successful upward transition on the LR. Birds were more likely to move down the GR by walking/running whereas birds tended to jump over the entire LR. More collisions with the food reward bowl were seen for the LR. In the group tests, birds preferred to use the GR, with more transitions seen at all timepoints. However, in these tests, birds preferred to rest on the LR with greater numbers of birds counted on this type of ramp during scan sampling at all timepoints.

DISCUSSION

Behavioural results suggest that the GR was easier for the birds to use than the LR, particularly on the downward transition. The GR was also less likely to result in collisions. However, the upward transition may be more difficult on the GR for some birds, potentially because of the inability to pause on a level surface during the transition. The results suggest that the GR was preferred by pullets for moving between a raised area and the ground but the LR was preferred for resting.

Limited Associations between Keel Bone Damage and Bone Properties Measured with Computer Tomography, Three-Point Bending Test, and Analysis of Minerals in Swiss Laying Hens

Keel bone damage is a wide-spread welfare problem in laying hens. It is unclear so far whether bone quality relates to keel bone damage. The goal of the present study was to detect possible associations between keel bone damage and bone properties of intact and damaged keel bones and of tibias in end-of-lay hens raised in loose housing systems. Bones were palpated and examined by peripheral quantitative computer tomography (PQCT), a three-point bending test, and analyses of bone ash. Contrary to our expectations, PQCT revealed higher cortical and trabecular contents in fractured than in intact keel bones. This might be due to structural bone repair after fractures. Density measurements of cortical and trabecular tissues of keel bones did not differ between individuals with and without fractures. In the three-point bending test of the tibias, ultimate shear strength was significantly higher in birds with intact vs. fractured keel bones. Likewise, birds with intact or slightly deviated keel bones had higher mineral and calcium contents of the keel bone than birds with fractured keel bones. Calcium content in keel bones was correlated with calcium content in tibias. Although there were some associations between bone traits related to bone strength and keel bone damage, other factors such as stochastic events related to housing such as falls and collisions seem to be at least as important for the prevalence of keel bone damage.

Selenium supplementation can protect from enhanced risk of keel bone damage in laying hens exposed to cadmium

The aim of this study was to investigate whether selenium (Se) supplementation can provide protection from an enhanced risk of keel bone damage (KBD) in laying hens due to the cadmium (Cd) toxicity associated with sub-chronic exposure.

Comparisons of bone properties and keel deformities between strains and housing systems in end-of-lay hens

Susceptibility of caged layers to osteoporosis and cage layer fatigue has generated interest in newer housing systems that favor increased load-bearing activities. However, high incidences of fractures incurred during lay period have been reported in these newer systems. This study is aimed at determining the housing and strain effects on bone properties: dry weight, percentage ash content, cortical density (CBD), cortical thickness (CBT), and keel bone deformities. Tibia, femur, and keel from Hy-Line Brown (HB), Hy-Line Silver Brown (SB), and Barred Plymouth Rock (BR) hens housed in conventional cages (CC), cage-free (CF), and cage-free with range (outdoor access; R) were studied. At 78 wk, 60 hens from each strain and housing system combination were euthanized and bones were excised for analysis. Quantitative computed tomography (QCT) was used to measure CBD and CBT in each bone. Three-dimensional images of keels were generated from software using QCT scans to analyze the deformities. Tibiae CBT was greater (P < 0.01) in BR compared to other two strains. Between housing systems, CBT was greater (P < 0.05) for mid and distal tibia of R and CF compared to CC. Tibiae and femoral cortex were denser (P < 0.05) in BR compared to HB and SB. There was no effect of housing system for femur CBD, but CBD was greater (P < 0.05) for middle and distal tibia of birds housed in R compared to CC. CBD for keel bone was greater (P < 0.05) in CF and R birds compared to CC birds. The housing system did not influence the dry bone weight and ash percentage of tibiae and femur. Each housing system was associated with high prevalence (>90%) of keel deformities and the housing and genotype influenced the type of deformity. These findings indicate that range and cage-free housing may have beneficial impact on tibia and keel bone integrity compared to conventional cages but the improvement may not be sufficient to prevent fractures or deformities of keel.