Prevalence Of Keel Bone Fractures Research Articles

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

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

Strain differences and effects of different stocking densities during rearing on the musculoskeletal development of pullets

There are few published studies on the effect of stocking density (SD) of pullets, particularly between different genetic lines. The objectives of this study were to determine if strain or SD affects musculoskeletal development of pullets and determine any impact on the productivity and keel bone health of adult hens. Lohmann Selected Leghorn Lite (LSL), Dekalb White (DW), and Lohmann Brown (LB) pullets were reared at 4 different SD (247 cm2/bird, 270 cm2/bird, 299 cm2/bird, and 335 cm2/bird) in large cages furnished with elevated perches and a platform. At 16 wk of age, the keel bone, the muscles of the breast, wings, and legs, and the long bones of the wings and legs were collected to compare keel bone development, muscle growth, and bone breaking strength (BBS) between strain (adjusted for bodyweight) and SD treatments. Stocking density did not have an effect on the metasternum length, height, or area of the keel bone, the weights of the bicep brachii, pectoralis major or pectoralis minor, or the BBS of any of the selected bones. However, strain differences were found for all keel bone characteristics, all muscle weights, and the majority of BBS measures. The keel metasternum, height, and overall area of the keel bone were found to be smaller in LB pullets compared with LSL and DW pullets (P < 0.0001); however, cartilage length and overall percentage of the cartilage present on the keel bone was greatest in LB pullets (P < 0.0001). Leg muscles were heaviest in LB pullets (P < 0.05); however, breast muscles were heavier in LSL and DW pullets (P < 0.0001). Lohmann Brown pullets had lower BBS of the tibia (P < 0.0001) and femur (P < 0.0001) compared with LSL and DW pullets, whereas DW pullets had greater BBS of the humerus (P = 0.033). Additionally, there was a higher prevalence of keel bone fractures at 50 wk of age in LB hens compared with DW (P = 0.0144). Overall, SD during rearing used in this study had little impact on the musculoskeletal growth of pullets; however, significant differences were found between strains which may reflect strain-specific behavior. Additionally, differences in keel bone development between strains may lead to differences in keel bone damage in adult hens.

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.

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.

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.

Behavioral Differences of Laying Hens with Fractured Keel Bones within Furnished Cages.

High prevalence of keel bone fractures in laying hens is reported in all housing systems. Keel fractures have been associated with pain and restricted mobility in hens in loose housing. The objective was to determine whether keel fractures were associated with activity of hens in furnished cages. Thirty-six pairs of LSL-Lite hens (72 weeks) were enrolled in the study. One hen with a fractured keel and one hen without were identified by palpation in each of 36 groups of hens housed in either 30- or 60-bird cages stocked at 750 cm2/hen. Behavioral activity of each hen was recorded by four observers blind to keel status using focal animal sampling for 10 min within a 2-h period in the morning (08:00–10:00), afternoon (12:00–14:00), and evening (17:00–19:00). All hens were observed during each of the three sample periods for 3 days totaling 90 min, and individual hen data were summed for analysis. Hens were euthanized 48 h after final observations, dissected, and classified by keel status: F0 (no fracture, N = 24), F1 (single fracture, N = 17), and F2 (multiple fractures, N = 31). The percentages of time hens performed each behavior were analyzed using a mixed procedure in SAS with fracture severity, body weight, cage size, rearing environment, and tier in the model. Fracture severity affected the duration of perching (P = 0.04) and standing (P = 0.001), bout length of standing (P < 0.0001), and location (floor vs. perch) of resting behaviors (P = 0.01). F2 hens perched longer than F0 hens, 20.0 ± 2.9 and 11.6 ± 3.2%. F2 hens spent less time standing, 15.2 ± 1.5%, than F0 and F1 hens, 20.7 ± 1.6 and 21.6 ± 1.8%. F2 hens had shorter standing bouts (22.0 ± 4.2 s) than both F0 and F1 hens, 33.1 ± 4.3 and 27.4 ± 4.4 s. Non-fractured hens spent 80.0 ± 6.9% of total resting time on the floor, whereas F1 and F2 hens spent 56.9 ± 12.4 and 51.5 ± 7.7% resting on the floor. Behavioral differences reported here provide insight into possible causes of keel damage, or alternatively, indicate a coping strategy used to offset pain or restricted mobility caused by keel fractures.

Early Onset of Laying and Bumblefoot Favor Keel Bone Fractures.

Simple SummaryNumerous studies have documented a high prevalence of keel bone fractures in laying hens. In this longitudinal study, 80 white and brown laying hens were regularly checked for keel bone deviations and fractures while egg production was individually monitored. About 62% of the hens had broken keel bones at depopulation. More new fractures occurred during the time when laying rates were highest. Hens with broken keel bones at depopulation had laid their first egg earlier than hens with intact keel bones. All birds with bumblefoot on both feet had a fracture at depopulation.Numerous studies have demonstrated influences of hybrid, feed, and housing on prevalence of keel bone fractures, but influences of behavior and production on an individual level are less known. In this longitudinal study, 80 white and brown laying hens were regularly checked for keel bone deviations and fractures while egg production was individually monitored using Radio Frequency Identification (RFID) from production until depopulation at 65 weeks of age. These focal birds were kept in eight pens with 20 hens per pen in total. About 62% of the hens had broken keel bones at depopulation. The occurrence of new fractures was temporally linked to egg laying: more new fractures occurred during the time when laying rates were highest. Hens with fractured keel bones at depopulation had laid their first egg earlier than hens with intact keel bones. However, the total number of eggs was neither correlated with the onset of egg laying nor with keel bone fractures. All birds with bumblefoot on both feet had a fracture at depopulation. Hens stayed in the nest for a longer time during egg laying during the ten days after the fracture than during the ten days before the fracture. In conclusion, a relationship between laying rates and keel bone fractures seems likely.

Do Laying Hens with Keel Bone Fractures Experience Pain?

The European ban on battery cages has forced a change towards the use of non-cage or furnished cage systems, but unexpectedly this has been associated with an increased prevalence of keel bone fractures in laying hens. Bone fractures are acutely painful in mammals, but the effect of fractures on bird welfare is unclear. We recently reported that keel bone fractures have an effect on bird mobility. One possible explanation for this is that flying becomes mechanically impaired. However it is also possible that if birds have a capacity to feel pain, then ongoing pain resulting from the fracture could contribute to decreased mobility. The aim was to provide proof of concept that administration of appropriate analgesic drugs improves mobility in birds with keel fracture; thereby contributing to the debate about the capacity of birds to experience pain and whether fractures are associated with pain in laying hens. In hens with keel fractures, butorphanol decreased the latency to land from perches compared with latencies recorded for these hens following saline (mean (SEM) landing time (seconds) birds with keel fractures treated with butorphanol and saline from the 50, 100 and 150 cm perch heights respectively 1.7 (0.3), 2.2 (0.3), p = 0.05, 50 cm; 12.5 (6.6), 16.9 (6.7), p = 0.03, 100 cm; 20.6 (7.4), 26.3 (7.6), p = 0.02 150 cm). Mobility indices were largely unchanged in birds without keel fractures following butorphanol. Critically, butorphanol can be considered analgesic in our study because it improved the ability of birds to perform a complex behaviour that requires both motivation and higher cognitive processing. This is the first study to provide a solid evidential base that birds with keel fractures experience pain, a finding that has significant implications for the welfare of laying hens that are housed in non-cage or furnished caged systems.