Keel Bone Fractures Research Articles

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.

The Role of Egg Production in the Etiology of Keel Bone Damage in Laying Hens.

Keel bone fractures and deviations belong to the most severe animal welfare problems in laying hens and are influenced by several factors such as husbandry system and genetic background. It is likely that egg production also influences keel bone health due to the high demand of calcium for the eggshell, which is, in part, taken from the skeleton. The high estrogen plasma concentration, which is linked to the high laying performance, may also affect the keel bone as sexual steroids have been shown to influence bone health. The aim of this study was to investigate the relationship between egg production, genetically determined high laying performance, estradiol-17ß concentration, and keel bone characteristics. Two hundred hens of two layer lines differing in laying performance (WLA: high performing; G11: low performing) were divided into four treatment groups: Group S received an implant containing a GnRH agonist that suppressed egg production, group E received an implant containing the sexual steroid estradiol-17ß, group SE received both implants, and group C were kept as control hens. Between the 12th and the 62nd weeks of age, the keel bone of all hens was radiographed and estradiol-17ß plasma concentration was assessed at regular intervals. Non-egg laying hens showed a lower risk of keel bone fracture and a higher radiographic density compared to egg laying hens. Exogenous estradiol-17ß was associated with a moderately higher risk of fracture within egg laying but with a lower risk of fracture and a higher radiographic density within non-egg laying hens. The high performing layer line WLA showed a significantly higher fracture risk but also a higher radiographic density compared to the low performing layer line G11. In contrast, neither the risk nor the severity of deviations were unambiguously influenced by egg production or layer line. We assume that within a layer line, there is a strong association between egg production and keel bone fractures, and, possibly, bone mineral density, but not between egg production and deviations. Moreover, our results confirm that genetic background influences fracture prevalence and indicate that the selection for high laying performance may negatively influence keel bone health.

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.

Keel impacts and associated behaviors in laying hens

Factors contributing to the development of keel bone damage are not well understood. This study aimed to identify behaviors and cage structures associated with acceleration events experienced by individual hens at their keels as the birds navigated their enriched colony cage environments. Additionally, we aimed to characterize the accelerations associated with these behaviors, as we postulated that behaviors associated with higher accelerations may be more likely to lead to keel bone damage. Sixty five 19 week old Hyline W36 hens were placed in each of 12 enriched colony cages. Ten focal hens per cage were selected for observation. Each hen was fitted with a jacket which contained a tri-axial accelerometer with an external sensor that was fitted into a small pocked over the hen’s keel. The logger recorded any time that the hen sustained an acceleration event at the keel (>12 G-units). Logger output was matched with video data, allowing us to describe the behavior of the affected bird at the time of the acceleration event recorded at the keel. Data on each bird were collected continuously over two 3-week periods, when the hens were between 52–60 and 74–83 weeks of age. Collisions accounted for nearly 81% of observed acceleration events with acceleration peaks of at least 20 G-units. The majority of collisions were with the perch and were sustained mainly as the hen attempted to ascend onto it. It has previously been reported that the prevalence of keel bone fractures is higher among hens housed in cages that do versus do not contain perches. This study lends support to the growing body of evidence indicating that interactions with perch contribute to the keel bone damage sustained by laying hens housed in enriched colony cage systems, however, the relationship between acceleration events and occurrence of keel bone damage has yet to be directly assessed.

Keel bone fractures are associated with individual mobility of laying hens in an aviary system

Keel bone fractures (KBF) in laying hens have been shown to cause pain and impair mobility under experimental conditions. However, it is not known how KBF relates to the mobility of individual hens housed in aviary systems. For the current study, 120 focal hens (60 Lohmann Brown (LB) and 60 Lohmann Selected Leghorn (LSL)) were kept in six identical pens equipped with a commercially relevant aviary system (20 LSL focal hens + 205 LB or 20 LB focal hens + 205 LSL per pen, respectively). Data on hen mobility were recorded at 21, 24, 27, 31, 35, 39, 44, 48, 52, 57 and 61 weeks of age. Infrared receivers were attached to the legs of focal hens. They recorded zone-specific codes between five zones (litter, lower tier, nest boxes, top tier, and wintergarden) at a frequency of 1 Hz for six consecutive days per week of age. At the end of each data collection period, hens were radiographed to assess keel bone fracture severity. Data were analysed using (generalized) linear mixed effect models. With increasing KBF severity, LB hens spent more time in the top tier (p = 0.005) and less time in the litter zone (p < 0.0001) and in the lower tier (p = 0.001). Independent of KBF, LB hens spent less time in the wintergarden (p = 0.011) and in the lower tier (p = 0.002) and more time in the top tier (p = 0.009) with increasing age. The likelihood of crossing more than one zone within a movement (e.g., jumping from the top tier to the litter directly) increased with increasing KBF severity (p = 0.036). Lohmann Selected Leghorn hens spent most time in the nest box zone and top tier and had few transitions between zones. With increasing age, LSL hens spent less time in the nest box zone (p = 0.018) and more time in the top tier (p = 0.006). Irrespective of strain, hens crossed fewer zones with increasing age (LB: p = 0.009, LSL: p = 0.002). Our findings indicate that hens having KBF prioritized paths among the upper tiers (i.e., mostly between nest box zone and top tier) over paths among the mid and lower tiers (i.e., between litter, lower tier and nest box zone). We conclude that behavioural adaptation to pain, the accessibility of resources as well as social factors might be important mechanisms driving individual mobility in response to KBF.

Laying hen’s mobility is impaired by keel bone fractures and does not improve with paracetamol treatment

Keel bone fractures (KBF) in laying hens pose a severe problem for animal welfare as they are likely to be associated with pain and suffering. Furthermore, they are suspected to hinder or restrict hens in their performance of natural species-specific behaviour. The aim of this study was to determine whether KBF affect laying hen behaviour in a non-cage system and whether this alteration is caused by pain. Forty Brown Nick and 40 Nick Chick hens were individually marked, and video recorded in eight experimental pens containing two perches with a platform attached to a ramp to facilitate access, an elevated nest box with platform for landing, drinker, feeder and litter. Data was collected at 37 and 39 weeks of age (WoA) on two consecutive days each at three time points per day. Paracetamol was administrated via drinking water either during the 37th or the 39th WoA. Additionally, activity assessments were done at 26, 28, and 30 WoA to detect differences pre-fracture. To assess the keel bone (KB) state, hens were radiographed at 30, 37 and 39 WoA and KB categorised as having no fracture, healed fracture(s) or fractures with a visible fracture gap. The odds of perch or nest access (i.e., vertical locomotion) decreased when a fracture gap was visible (p = 0.004) but the walking pace on ramps leading to the perches was not affected by KBF. Paracetamol did neither reverse the decrease in mobility behaviour nor did it affect the walking pace on the ramp. Of the hens with fractures featuring a visible fracture gap, those receiving paracetamol performed less rapid comfort behaviours (e.g., wing flapping) than hens receiving vehicle (i.e. water) only (p = 0.04). Preening and dustbathing duration was increased with the administration of paracetamol (p = 0.02) though was unaffected by KBF in this study. No difference was found in activity before the fracture(s) occurred. In conclusion, we show that KBF affect laying hen mobility behaviour in non-cage systems and thus a reduction of KBF would improve laying hen welfare.

Health of Commercial Egg Laying Chickens in Different Housing Systems.

To determine which type of egg-laying hen housing was best for the chickens, the workers in those housing systems, the environment, and society based on food safety and affordability, a combined research project involving egg suppliers, food manufacturers, food service representatives, and food retailers, as well as research institutions and nongovernmental organizations, was performed. This study reports the hen health and welfare portion based upon veterinary health inspections and compared mortality rates, skeletal abnormalities, causes of death determined by necropsy, and titers to infectious bronchitis and Newcastle disease viruses. Birds were housed on a preexisting Midwest layer complex, which consisted of conventional cages (CC). New houses were built adjacent to the CC house where enriched colony cages (EC) and an aviary system (AV) were installed. Two flock cycles from housing to 78 wk of age were followed. Total mortality was greatest for AV, while CC and EC birds were similar. Keel bone fractures were greatest for AV, next greatest for EC, and least for CC birds. Other skeletal abnormalities were greatest for AV birds. Birds dying from being caught in the structure, pick out, and persecution was most frequent for AV and next most frequent for EC, but nonexistent with CC birds. Infectious pododermatitis (bumblefoot) was most frequent for AV, next most frequent for EC, and essentially nonexistent for CC birds. There was little to no effect on antibody titers based upon housing type. Based upon these findings, it appears that EC housing is better for the health and welfare of egg-laying chickens than CC or AV housing.

Frequency of falls in commercial aviary-housed laying hen flocks and the effects of dusk phase length

Even though aviary systems provide a range of benefits for laying hens in terms of animal welfare, falls and collisions have been observed in experimental settings. These falls are likely stressful for the birds and are thought to be linked to the known high prevalence of keel bone fractures in aviary-housed hens. We investigated the frequency of falls and fall patterns such as collisions, height and cause of fall as well as the prevalence of keel bone damage in commercial aviary-housed Swiss layer flocks and the relationship with time of day and week of age. We also examined the effect of a prolonged artificial dusk length on the number of falls. In total, eight commercial Swiss laying hen farms with two barns each were used and dusk length was adjusted to vary continuously between 14 and 76 min over all 16 barns. Video recordings and palpation of the keel bone to assess fractures, deviations and alterations of 100 hens per flock were conducted in week of age (WOA) 20 and 45. Videos were analysed after lights on, at mid-day, during the whole dusk phase as well as after lights off. Statistical analyses were conducted using generalized as well as linear mixed-effects models. Fall frequency was highest during the dusk phase in WOA 20 compared with any other observed times of day and WOA 45 (all combinations: p < 0.001). In addition, the likelihood of falls including a collision was higher at 20 compared with WOA 45 (p = 0.05) and after lights on compared with the dusk phase and after lights off (both p < 0.001). The majority of falls were observed to occur from the top level of the aviary compared with the middle or lower levels (top level: 55.3% vs. middle level: 29.3% vs. lower level: 8.5%). A longer dusk phase did not reduce the number of falls but affected their cause: falls were less likely to be caused by failed landings with increasing dusk length (p = 0.036). The prevalence of keel bone fractures increased from 15.4% in WOA 20 to 64 % in WOA 45 and was not linked with the number of falls. Even though the majority of falls were observed during the dusk phase, prolonging the dusk phase alone did not suffice to reduce falls. Thus, additional factors such as aviary design and management should be further investigated to reduce falls in aviary systems and increase the welfare of laying hens.

Keel bone fractures affect egg laying performance but not egg quality in laying hens housed in a commercial aviary system

The aim of this study was to investigate the effect of keel bone fracture (KBF) severity and healing activity on individual productivity of laying hens. Focal hens (75 Lohmann Selected Leghorn (LSL), 75 Lohmann Brown (LB)) were housed alongside non-focal hens in 10 identical pens containing a commercial aviary system (15 focal hens per pen). Eggs of focal hens were identified by orally administering a dye on 3 consecutive days, resulting in a hen-specific color pattern in the yolk. Eggs were collected at 7 time points (37 to 61 weeks of age; WOA) for 5 d to determine individual laying performance and to assess egg quality. Radiographs were performed to score KBF severity on a continuous scale. Healing activity was scored as inactive, healing, or fresh. Linear mixed effects models were used for statistical analyses. We found an association between KBF severity and reduced egg laying performance with increasing age (P = 0.005). At 37 WOA, egg laying performance was similar across KBF severities, whereas at 61 WOA, performance in hens with the highest observed KBF severity was 16.2% lower than in hens without fractures. Hens with fresh fractures had a lower performance than hens with healing and inactive fractures at 37 WOA but higher performance at 61 WOA (P = 0.02). Egg quality parameters were not affected by fractures but were associated with an age × hybrid interaction (egg mass: P = 0.039, shell breaking strength: P = 0.03, shell width: P = 0.001). In conclusion, hens could maintain high performance irrespective of fracture severity until shortly after peak of lay, but seemed to redirect available resources towards fracture healing if a fresh fracture was present. At the end of lay, the negative effect of KBF fracture severity on individual production amplified indicating that hens were no longer able to cope with the physiological challenge of a fracture.

Welfare of layers housed in small furnished cages on Danish commercial farms: the condition of keel bone, feet, plumage and skin

ABSTRACT1. An on-farm assessment of keel bone, feet, plumage and skin damage was conducted in layers in small furnished cages to evaluate welfare implications.2. Thirteen farms participated, all housing Lohmann LSL layers in systems allowing 8 or 10 hens per cage.3. Each flock was visited at three different ages: 32, 62 and 77 weeks. During each visit, 100 hens were examined for keel bone fractures and deviations, plumage damage, body wounds, foot pad lesions, bumble feet, missing toes and toe wounds.4. A deterioration with age of the condition of the plumage and keel bone was found (P < 0.001). At 77 weeks of age, 16% of the birds had poor plumage, and 43% of the birds had keel bone damage. In contrast, foot pad lesions were most prevalent at 32 weeks of age (13%), whereas the other foot injuries and body wounds remained at a relatively low level throughout the three ages examined.5. Prevention of damage to the keel bone, plumage and foot pads should therefore be considered when aiming to improve welfare of laying hens housed in small furnished cages.

The effect of experience of ramps at rear on the subsequent ability of layer pullets to negotiate a ramp transition

In commercial situations, laying hens must negotiate levels to reach resources such as food, water and litter. Providing ramps in aviary systems reduces collisions and resultant keel bone fractures in adults. We investigated whether providing ramps during rear improved the ability of birds to transition between levels.Chicks were reared commercially in two flocks both of which provided access to raised structures from three weeks of age. One flock had no ramps, but the other flock was provided with additional access to two types of ramp (wooden ladders, and grids formed from commercial poultry slats placed at an angle). At 8 weeks of age, 64 birds (32 from each rearing condition) were transferred to an experimental facility. At 10 weeks of age, 32 pullets from each group were trained to run to a food reward. During testing at 12–14 weeks of age the pullets accessed the food reward by moving up or down a ramp. The pullets’ behaviours and time taken to complete the task were recorded. Ramp use over three days was also observed in a room replicating a small-scale single-tier system. Four groups of 16 birds aged 12–14 weeks were housed for three days and the number of transitions between the raised tier and litter were recorded.For upward transitions, more ramp-reared birds than control birds succeeded in reaching the food reward for both ladder (52% vs 13%) and grid ramps (74% vs 42%). Birds from the ramp-reared group took significantly less time to complete an upwards transition (68.8s ± 49.3) than the control group (100s ± 37.6) (p = 0.001). In addition, the control group showed more behaviours indicative of hesitancy (moving away, head orientations, ground pecking and crouching) before transitioning, and signs of difficulty when making upward transitions (crouched walks, pauses, turning, returning and escape attempts). In the group housing observations, the ramp reared groups had almost double the number of transitions between the slats and litter on day one compared to the control group. This difference was reduced by day three.In summary, this suggests there are positive effects of providing ramp experience during rear shown by any combination of bird mobility, strength or cognitive ability leading to an increase in apparent confidence in older pullets. It is not known whether these benefits persist through to the laying period, but no detrimental effects were noted so we suggest that ramps should be included from the early rearing period onwards.

Modeling collisions in laying hens as a tool to identify causative factors for keel bone fractures and means to reduce their occurrence and severity.

Keel fractures represent a major productivity and welfare issue for the laying hen industry with greater than 50% of birds in recent surveys across various commercial operations and nations exhibiting some form of damage by end of lay. While the causes are likely multifactorial and influenced by age, diet, genetic line, and other factors, high energy collisions with house furnishings and conspecifics in the barn are believed to be a major contribution to the frequency and severity of factures. The current study applies a previously described ex vivo impact testing protocol to quantify susceptibility to keel bone damage across an extensive range of collision energies and ages. We also link fracture susceptibility with bone and physiological measures likely to influence skeletal resilience. Further, we applied the impact testing protocol to evaluate the benefit of an omega-3 enriched diet to improve bone health and reduce fracture susceptibility. Our results indicated that fracture susceptibility increased rapidly from 23 weeks of age, peaking at 49.5 weeks of age and thereafter decreasing. Fracture susceptibility also varied with multiple natural characteristics of bone, including mineral density, though the nature of that relationship was dependent on whether an old fracture was present. Severity of the experimental fracture demonstrated considerable variation with collision energy and biomechanical properties. An omega-3 enhanced diet provided a protective effect against fractures, though only in terms of collision energies that were relatively low. In conclusion, the impact testing protocol provided a unique means to assess fracture susceptibility and quantify the role of likely influencing bird-level biological factors, both those that vary naturally as well as when altered through specific interventions.

A Reliable Method to Assess Keel Bone Fractures in Laying Hens From Radiographs Using a Tagged Visual Analogue Scale.

Up to 97% of laying hens housed in aviary systems are affected by keel bone fractures. Due to the scope of the problem, multiple efforts investigating causes and consequences of fractures have been conducted. The most frequently used techniques to detect fractures lack accuracy and provide only vague information (palpation) or cannot be conducted longitudinally (dissection). Radiographic imaging overcomes these weaknesses as it allows longitudinal observations and provides detailed information for individual fractures of which a single keel may have several at different locations and of different origins. However, no standardized system exists to assess fracture severity from radiographs if multiple fractures are present. The aim of this study was therefore to test the reliability of a scoring system assessing the aggregate severity of multiple fractures, taking into account the characteristics of all present fractures (e.g., locations, callus formation, width of fracture gaps). We developed a scoring system based on a tagged visual analogue scale, ranging from score 0 (no fracture) to score 5 (extremely severe) with intermediate tags for scores 1, 2, 3, and 4. A catalog of example scores was provided to describe the range of each score visually. An online tutorial with an introduction, training and scoring session was completed by 14 participants with varying experience involving laying hens and keel bone damage. For inter-observer reliability, we found an Intraclass correlation coefficient (ICC) of 0.985 with a 95% confidence interval of 0.974 < ICC < 0.993 (average-rating, absolute-agreement, two-way random-effects model). Intraclass correlation coefficient for intra-observer reliability was 0.923 with a 95% confidence interval of 0.879 < ICC < 0.951 (single-rating, absolute-agreement, two-way mixed-effects model). Intra-observer reliability ranged from 0.704 to 1.0 indicating excellent agreement and similar ratings across and within participants. Further, high ICCs suggest that the introduction and the training sessions provided were adequate tools to prepare observers for the assessment task despite various backgrounds of the participants. Nonetheless, the validity of this scoring system needs to be investigated further in order to link responses of interest and biological relevance with the specific severity values resulting from our scoring system.

Validation of an accelerometer to quantify inactivity in laying hens with or without keel-bone fractures

Validation of an accelerometer to quantify inactivity in laying hens with or without keel-bone fractures

Use of aerial perches and perches on aviary tiers by broiler breeders

Perching, especially during the night, is an innate behaviour of chickens and the provision of perches is mandatory for laying hens in multiple countries. We examined whether broiler breeders of the fast (Ross 308) and relatively slow (Sasso) growing hybrids used aerial perches (P) and perches on aviary tiers (A) during rearing and production and how it affected welfare and production in comparison to controls without perches. Two hybrids and three treatments (control, aviary, perch) were employed in a cross-factorial arrangement. Control pens consisted of litter, raised slats, group nests, two feeder and one drinker lines. Perch-pens (P) included eight wooden perches in an A-frame configuration at 25, 50, 75, 100 cm above the slats and aviary-pens (A) included four aviary tiers with wooden bars and perches arranged as a platform (70 × 450 cm) at 55, 68, 115, and 138 cm above the slats. Each treatment combination was replicated three times resulting in a total of 18 pens. Welfare parameters of hens were assessed at 45 weeks and production was monitored continuously. Both hybrids used perches increasingly with age and predominantly at night (both tests P < 0.0001). Birds in control pens perched on the grill above the feeders and drinking lines more than birds in A or P (P = 0.0002) and perches were more used in A than P pens (P = 0.002). More brood eggs were collected in control pens than in the other treatments (P = 0.02) and A-pens yielded more floor eggs (P = 0.007) than control pens and P-pens. Keel bone fractures were less frequent than in laying hens but hens in A and P pens had more keel bone fractures than hens in control pens (P = 0.02) and Sasso had more than Ross (P = 0.002). In conclusion, our results suggest that broiler breeders are highly motivated to access aerial perches or perches on aviary tiers similar to laying hens with a similar welfare problem of keel bone fractures. Perches had no influence on hatching rates but measures should be taken against floor eggs to avoid a loss of brood eggs.

The Influence of Keel Bone Damage on Welfare of Laying Hens.

This article reviews current knowledge about welfare implications of keel bone damage in laying hens. As an initial part, we shortly describe the different conditions and present major risk factors as well as findings on the prevalence of the conditions. Keel bone damage is found in all types of commercial production, however with varying prevalence across systems, countries, and age of the hens. In general, the understanding of animal welfare is influenced by value-based ideas about what is important or desirable for animals to have a good life. This review covers different types of welfare indicators, including measures of affective states, basic health, and functioning as well as natural living of the birds, thereby including the typical public welfare concerns. Laying hens with keel bone fractures show marked behavioral differences in highly motivated behavior, such as perching, nest use, and locomotion, indicating reduced mobility and potentially negative affective states. It remains unclear whether keel bone fractures affect hen mortality, but there seem to be relations between the fractures and other clinical indicators of reduced welfare. Evidence of several types showing pain involvement in fractured keel bones has been published, strongly suggesting that fractures are a source of pain, at least for weeks after the occurrence. In addition, negative effects of fractures have been found in egg production. Irrespective of the underlying welfare concern, available scientific evidence showed that keel bone fractures reduce the welfare of layers in modern production systems. Due to the limited research into the welfare implications of keel bone deviation, evidence of the consequences of this condition is not as comprehensive and clear. However, indications have been found that keel bone deviations have a negative impact on the welfare of laying hens. In order to reduce the occurrence of the conditions as well as to examine how the affected birds should be treated, more research into the welfare implications of keel bone damage is needed. Research should focus on effects of genetic lines, genetic selection, housing, and nutrition for the development, prevalence, and severity of these conditions, preferably conducted as longitudinal and/or transnational studies.

Feeding from perches in an aviary system reduces aggression and mortality in laying hens

Some commercial aviary systems for laying hens allow birds to access feed by standing on perches instead of platforms. Despite reports that providing laying hens with perches relates to reduced aggression and cannibalism, and increased prevalence of keel bone damage, the impact of feeding from perches on behaviour, health, and production has not been investigated. The current work studied the effects of feeding either from perches (Perch Treatment) or platforms (Platform Treatment) on behaviour, health, and production. The experiment was conducted in a quasi-commercial barn divided into 20 identical pens with 196 hens per pen to compare treatment (Perch vs. Platform) and hybrid (Nick Chick vs. Brown Nick) in a 2 × 2 factorial design. We analysed behaviour (from video recordings taken at 30, 37, and 51 weeks of age), health (at 29 and 65 weeks of age), feather condition (at 21, 44, and 65 weeks of age) and productivity parameters (collected daily from 18 to 65 weeks of age). Hens of the Perch Treatment showed less aggression at the feeder (z-value = − 1.942, p = 0.05), less jostling followed by feeding (at 30 weeks of age: z-value = − 4.191, p < 0.001; and 37 weeks of age: z-value = − 3.059, p = 0.022; but not at 51 weeks of age: p = 0.823) and followed by a behaviour other than feeding (z-value = − 7.075, p < 0.001), as well as more body instability (balance movements and falls combined) behaviours (Brown Nick: z-value = 4.338, p < 0.001, Nick Chick: z-value = 7.550, p < 0.001) than hens from the Platform Treatment. There was no difference in keel bone fractures between the treatments (p = 0.555). In the Perch Treatment, we recorded a tendency for lower overall mortality (t-value = − 1.807, d.f.= 17, p = 0.089) and the Brown Nick hybrid had lower mortality resulting from cannibalism (t-value = − 2.955, d.f. = 8, p = 0.021), laid more eggs (z-value = − 2.853, p = 0.022), and had a greater feed conversion ratio (z-value = 3.947, p < 0.001) than in the Platform Treatment. Due to reduced aggression and jostling, as well as a tendency for lower overall mortality, we conclude that the Perch Treatment is a superior alternative with improved welfare to the Platform

Welfare Consequences of Omitting Beak Trimming in Barn Layers.

Beak trimming is used worldwide as a method of reducing the damage to feathers and skin caused by injurious pecking in laying hens. However, beak trimming also causes some welfare issues as trimming the beak results in pain and sensory loss. Due to this dilemma, there is an ongoing discussion in several European countries about whether to ban beak trimming. In this study, we investigated the welfare consequences of keeping layers with intact beaks and examined for links between injurious pecking damage and keel bone damage on an individual level. A study was conducted on 10 commercial farms housing laying hens in the barn system. Each farm participated with a flock of beak-trimmed hens (T) and a flock of non-trimmed (NT) hens that were visited around 32 and 62 weeks of age. During visits, the condition of plumage, skin, feet, and keel bone of 100 hens was assessed. Mortality was recorded by the producers. NT flocks had a lower prevalence of hens with good plumage condition around 32 weeks of age (94.1 vs. 99.6%, P < 0.001) and a higher prevalence of hens with poor plumage condition at 62 weeks of age (63.6 vs. 15.2%, P < 0.001) compared with T flocks. The prevalence of hens with keel bone deviations, with both keel bone fractures and deviations and with body wounds, was higher in NT flocks compared with T flocks at both ages (P < 0.001). Accumulated mortality from placement to end of production tended to be higher in NT flocks compared with T flocks (14.2 vs. 8.6%; P = 0.06). The prevalence of keel bone damage was higher among hens with poor plumage condition than hens with moderate/good plumage condition (31.5 vs. 22.2%; P < 0.001). Thus, omitting beak trimming had negative consequences for the condition of plumage, skin, and keel bone, and tended to increase mortality, highlighting the risk of reduced welfare when keeping layers with intact beaks. In addition, injurious pecking damage was found to be positively linked to keel bone damage. The causal relation is unknown, but we propose that fearfulness is an important factor.

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.

Perch use by broiler breeders and its implication on health and production

Broiler breeders are commonly kept without perches, although perching has been shown to be a high-priority behavior in laying hens. We studied whether broiler breeders used elevated perches of different lengths during the night and how access to perches affected health and production. Using the Ross 308 hybrid, pens offering 4 different perch spaces per bird (5, 10, 14, and 20cm) in a cross-over design were compared with pens without perches. The number of birds on perches at midnight were recorded 7 times during production. Prevalence of keel bone fractures, breast blisters, pododermatitis, and plumage quality of hens was assessed at 45 wk, and production was monitored daily. To determine subsequent effects on offspring, chicks from hens with and without perches were reared and their growth rate was assessed. Analysis found more broiler breeders perched at night when 14cm perch length per bird was provided than with less available perch length (P = 0.0005), but there was no difference between 14 and 20cm per bird. Perch use declined with age from about 50 to 20% (P <0.0001). The number of eggs and hatchability were not affected by treatment. During a period of high temperatures, mortality was lower in pens with perches (P = 0.001). Keel bone fractures were present in 1/4 of hens and were not affected by the presence of perches. The growth of chicks was not affected by the parent treatment. In conclusion, our results suggest that perches were chosen for roosting by broiler breeders depending on their age and did not impair production.