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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 cm 2 /bird, 270 cm 2 /bird, 299 cm 2 /bird, and 335 cm 2 /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., (Copyright © 2020. Published by Elsevier Inc.)

We determine interactive effect of a combined model of housing systems for rearing pullets and raising adult birds on bone quality. The LSL-Lite pullets were reared in either an aviary system (A) or conventional cages (C). At week 16, the birds were transferred either to the same housing type through the adult stage (A-A or C-C, for rearing and adult phase, respectively) or to enriched system (A-E or C-E, respectively). In the rearing stage, C cages housed 16 pullets/cage (week 0 to 6) and 8 pullets/cage (week 6 to 16) with a space allowance of 145 and 290 cm2/pullet, respectively; the rearing aviary housed 756 pullets/enclosure allowing 285 cm2/pullet (week 0 to 6) and 754 cm2/pullet (week 6 to 16). In the adult phase, C cages were 58.4 cm wide × 66.0 cm deep (482 cm2/pullet, 8 pullets/cage). For adult A, a commercial multi-tier aviary provided a space allowance >1000 cm2/hen system with litter area. Enriched system housed 60 birds/cage at 750 cm2/bird with perches, nest, and scratch mat. Bone samples were collected from the adult phase (week 73) and analysed for bone quality indices including bone breaking strength (BBS), total bone weight (TBW), ash content of the medullary (femur and tibia), pneumatic (humerus and keel), and radius bones. The A-A hens had the greatest (P < 0.05) TBW for medullary (femur and tibia) and pneumatic (humerus and keel) bones compared with hens from other housing models with exception of C-E hens. In addition, ash content was heavier (P = 0.048) for both A-A and C-E managed birds compared to the other housing. Birds in C-C system had the least score (P < 0.05) for TBW and ash content in all bone types. Regardless of the housing system, BBS was correlated (r = 0.60; P < 0.01) with the amount of ash and TBW, particularly for humerus and tibia. The results provide an insight on the impact of type of housing system in rearing and production stages on late cycle bone quality., (© 2019 Poultry Science Association Inc.)

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.

Standards for feeder (a.k.a. feed trough) space allowance (SA) are based primarily on studies in conventional cages where laying hens tend to eat simultaneously, limiting feeder space. Large furnished cages (FC) offer more total space and opportunities to perform a greater variety of behaviors, which may affect feeding behavior and feeder space requirements. Our objective was to determine the effects of floor/feeder SA on behavior at the feeder. LSL-Lite hens were housed in FC equipped with a nest, perches, and a scratch mat. Hens with SA of either 520 cm2 (Low; 8.9 cm feeder space/hen) or 748 cm2 (High; 12.8 cm feeder space/hen) per bird resulted in groups of 40 vs. 28 birds in small FC (SFC) and 80 vs. 55 in large FC (LFC). Chain feeders ran at 0500, 0800, 1100, 1400, and 1700 with lights on at 0500 and off at 1900 hours. Digital recordings of FC were scanned at chain feeder onset and every 15 min for one h after (5 scans × 5 feeding times × 2 d) to count the number of birds with their head in the feeder. All occurrences of aggressive pecks and displacements during 2 continuous 30-minute observations at 0800 h and 1700 h also were counted. Mixed model repeated analyses tested the effects of SA, cage size, and time on the percent of hens feeding, and the frequency of aggressive pecks and displacements. Surprisingly, the percent of birds feeding simultaneously was similar regardless of cage size (LFC: 23.0 ± 0.9%; SFC: 24.0 ± 1.0%; P = 0.44) or SA (Low: 23.8 ± 0.9%; High: 23.3 ± 1.0%; P = 0.62). More birds were observed feeding at 1700 h (35.3 ± 0.1%) than any at other time (P < 0.001). Feeder use differed by cage area (nest, middle, or scratch) over the d (P < 0.001). The frequency of aggressive pecks was low overall and not affected by SA or cage size. Frequency of displacements was also low but greater at Low SA (P = 0.001). There was little evidence of feeder competition at the Low SA in this study., (© The Author 2017. Published by Oxford University Press on behalf of Poultry Science Association.)

Osteoporosis in laying hens has been a production and welfare concern for several decades. The objective of this study was to determine whether differing opportunities for exercise during pullet rearing influences long-term bone quality characteristics in end-of-lay hens. A secondary objective was to assess whether differing opportunities for exercise in adult housing systems alters bone quality characteristics in end-of-lay hens. Four flock replicates of 588 Lohmann Selected Leghorn-Lite pullets were reared in either conventional cages (Conv) or an aviary rearing system (Avi) and placed into conventional cages (CC), 30-bird furnished cages (FC-S), or 60-bird furnished cages (FC-L) for adult housing. Wing and leg bones were collected at the end-of-lay to quantify bone composition and strength using quantitative computed tomography and bone breaking strength (BBS). At the end-of-lay, Avi hens had greater total and cortical cross-sectional area (P < 0.05) for the radius and tibia, greater total bone mineral content of the radius (P < 0.001), and greater tibial cortical bone mineral content (P = 0.029) than the Conv hens; however, total bone mineral density of the radius (P < 0.001) and cortical bone mineral density of the radius and tibia (P < 0.001) were greater in the Conv hens. Hens in the FC-L had greater total bone mineral density for the radius and tibia (P < 0.05) and greater trabecular bone mineral density for the radius (P = 0.027), compared to hens in the FC-S and CC. Total bone mineral content of the tibia (P = 0.030) and cortical bone mineral content of the radius (P = 0.030) and tibia (P = 0.013) were greater in the FC-L compared to the CC. The humerus of Conv hens had greater BBS than the Avi hens (P < 0.001), and the tibiae of FC-L and FC-S hens had greater BBS than CC hens (P = 0.006). Increased opportunities for exercise offered by the aviary rearing system provided improved bone quality characteristics lasting through to the end-of-lay., (© The Author 2017. Published by Oxford University Press on behalf of Poultry Science Association.)

Increased load-bearing exercise improves bone quality characteristics in a variety of species, including laying hens. Providing increased opportunities for exercise during the pullet rearing phase, a period of substantial musculoskeletal growth, offers a proactive approach to reducing osteoporosis by improving bone composition. The main objective of this study was to determine whether differing opportunities for exercise during rearing influences pullet musculoskeletal characteristics. Two flock replicates of 588 Lohmann Selected Leghorn-Lite pullets were reared in either standard, conventional cages (Conv) or an aviary rearing system (Avi) from day-old chicks until 16 wk of age. The keel bone and the muscles and long bones of the wings and legs were collected at 16 wk to measure muscle growth differences between rearing treatments and quantify bone quality characteristics using quantitative computed tomography (QCT) and bone breaking strength (BBS) assessment. Keel bone characteristics and muscle weights were adjusted for BW and analyses for QCT and BBS included BW as a covariate. At 16 wk of age, rearing system had an effect on the majority of keel bone characteristics (P < 0.05). The length of the keel metasternum, caudal tip cartilage length, and the overall percentage of cartilage present on the keel at 16 wk was greater in the Avi pullets compared to the Conv pullets (P < 0.01). Wing and breast muscle weights of the Avi pullets were greater than the Conv pullets (P < 0.001), but leg muscle weights were greater in the Conv pullets (P = 0.026). Avi pullets had greater total bone density, total cross-sectional area, cortical cross-sectional area, total bone mineral content, and cortical bone mineral content than Conv pullets for the radius, humerus, and tibia (P < 0.001). Avi pullets had greater BBS compared to the Conv pullets for the radius, humerus, and tibia (P < 0.01). Increased opportunities for exercise offered by the aviary rearing system increased muscle and bone growth characteristics in pullets at 16 wk of age., (© The Author 2017. Published by Oxford University Press on behalf of Poultry Science Association.)

High flock-level prevalence of keel-bone fractures and deviations in laying hens are commonly reported across various housing systems; however, few longitudinal studies exist, especially for furnished and conventional cage systems. Load-bearing exercise improves bone strength and mineral composition in laying hens and has the potential to reduce keel-bone damage, especially if exercise is allowed during critical periods of bone growth throughout the pullet rearing phase. The objective of this study was to determine the prevalence of keel-bone damage in laying hens housed in furnished and conventional cages, and assess whether opportunities for exercise during the pullet rearing phase influenced the prevalence of keel-bone damage throughout the laying period. Four flock replicates of 588 Lohmann Selected Leghorn-Lite pullets/flock were reared in either conventional cages (Conv) or an aviary rearing system (Avi) and placed into conventional cages (CC), 30-bird furnished cages (FC-S) or 60-bird furnished cages (FC-L) for adult housing. Keel-bone status was determined by palpation at 30, 50, and 70 wk of age. Age (P < 0.001) and rearing system (P < 0.001) had an effect on the presence of keel-bone fractures. The presence of fractures increased with age, and hens raised in the Avi system had a lower percentage of fractures (41.6% ± 2.8 SE) compared to hens reared in the Conv system (60.3% ± 2.9 SE). Adult housing system did not have an effect on the percentage of keel fractures (P = 0.223). Age had an effect on the presence of deviations (P < 0.001), with deviations increasing with age. Rearing system (P = 0.218) and adult housing system (P = 0.539) did not affect the presence of deviations. Keel fractures and deviations were strongly associated with each other at all ages: 30 wk: (P < 0.001); 50 wk: (P < 0.001); and 70 wk: (P < 0.001). Increased opportunities for exercise provided by an aviary rearing system reduced the prevalence of keel-bone fractures through the end-of-lay., (© 2017 Poultry Science Association Inc.)

Furnished rearing cages are becoming more widely available to replace conventional systems for pullets. To date, there is little information on how pullets develop perching behavior in furnished cages or how this varies among strains. The objective of this study was to evaluate the use of perches and a platform in a commercial furnished rearing "Combi-Cage" system by 3 pure-bred heritage strains of pullets (Rhode Island Red, Columbian Rock, and White Leghorn). Each cage had 4 elevated locations: one platform and 3 perches of differing heights and positions in the cage. The length of each cage was visually divided into 4 sections for observation. The number of birds using each section in each location was counted by one observer d per wk at 1200 h (d) from one to 14 wk of age and at 1600 h (night) right after lights were turned off from 4 to 14 wk of age. Mixed model repeated analyses were used to test effects of strain, age, and their interaction on the use of the platform, the 3 perches, and all 4 locations combined (vertical space use) at both time periods. GLM were used to compare overall use of the sections and locations. On average, pullets used vertical space more during the d than at night. There were also effects of age (P < 0.05) and strain (P < 0.05) on the use of the 4 locations in the cage at both time periods. Generally, the Columbian Rocks used the perches and platform the most, and Rhode Island Reds the least. The highest perch in the cage was rarely used and birds showed a preference for perching in sections that were closest to cage walls (P < 0.05). Differences across strains and low use of some perch locations indicate that the design of furnished rearing cages may still require improvements in order to ensure the furnishings are used by pullets as intended., (© 2016 Poultry Science Association Inc.)

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 cm(2)/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: F 0 (no fracture, N = 24), F 1 (single fracture, N = 17), and F 2 (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). F 2 hens perched longer than F 0 hens, 20.0 ± 2.9 and 11.6 ± 3.2%. F 2 hens spent less time standing, 15.2 ± 1.5%, than F 0 and F 1 hens, 20.7 ± 1.6 and 21.6 ± 1.8%. F 2 hens had shorter standing bouts (22.0 ± 4.2 s) than both F 0 and F 1 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 F 1 and F 2 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.

The objective of this study was to determine the effectiveness of a nonpenetrating captive bolt, Zephyr-E, for euthanasia of suckling and weaned pigs from 3 to 9 kg (5-49 d of age) using signs of insensibility and death as well as postmortem assessment of traumatic brain injury (TBI). The Zephyr-E was used by 15 stock people to euthanize 150 compromised pigs from 4 farrowing and nursery units from commercial farms and 2 research stations. Brainstem reflexes, convulsions, and heartbeat were used to assess insensibility, time of brain death, and cardiac arrest following Zephyr-E application. Skull fracture displacement (FD) was quantified from computed tomography (CT) scans (n = 24), macroscopic scoring was used to assess brain hemorrhage and skull fracture severity (n = 150), and microscopic scoring was used to assess subdural hemorrhage (SDH) and parenchymal hemorrhage within specific brain regions that are responsible for consciousness and vital function (n = 32). The Zephyr-E caused immediate, sustained insensibility until death in 98.6% of pigs. On average, clonic convulsions (CC) ceased in 82.2 s (± 3.4 SE), brain death was achieved in 144.9 s (± 5.4 SE), and cardiac arrest occurred in 226.5 s (± 8.7 SE). Time of brain death and cardiac arrest differed significantly among stock people (P = 0.0225 and P = 0.0369). Age was positively related to the duration of CC (P = 0.0092), time of brain death (P = 0.0025), and cardiac arrest (P = 0.0068) with shorter durations seen in younger pigs. Average FD was 8.3 mm (± 1.0 SE). Macroscopic scores were significantly different among weight classes for subcutaneous (P = 0.0402) and subdural-ventral (P = 0.0037) hemorrhage with the lowest severity hemorrhage found in the 9-kg weight category. Microscopic scores differed among brain sections (P = 0.0070) for SDH with lower scores found in the brainstem compared to the cerebral cortex and midbrain. Parenchymal hemorrhage differed among brain sections (P = 0.0052) and weight categories (P = 0.0128) with the lowest scores in the midbrain and brainstem and the 7- and 9-kg weight categories. The Zephyr-E was highly effective for the euthanasia of pigs up to 9 kg (49 d) based on immediate insensibility sustained until death. Postmortem results confirmed that severe skull fracture and widespread brain hemorrhage were caused by the Zephyr-E nonpenetrating captive bolt.

The objective of this study was to determine the effectiveness of a nonpenetrating captive bolt (NPCB), the Zephyr-Euthanasia (Zephyr-E), for euthanasia of neonatal piglets<72 h of age using signs of insensibility and death, as well as postmortem assessment of traumatic brain injury (TBI). The Zephyr-E was used by 10 stock people to euthanize 100 low viability neonatal piglets from 3 commercial farrowing units and 1 research farm. Brainstem reflexes, convulsions, and heartbeat were used to assess insensibility, time of brain death, and cardiac arrest after Zephyr-E application. Hemorrhage severity and skull fracture displacement (FD) were quantified from computed tomography scans (n=10), macroscopic scoring was used to assess brain hemorrhage and skull fracture (SK) severity (n=100), and microscopic scoring was used to assess subdural (SDH) and parenchymal (PH) hemorrhage within specific brain regions that are responsible for consciousness and vital function (n=10). All 100 piglets were rendered immediately insensible without return to sensibility. On average, clonic convulsions (CC) ceased in 101 s (±7.4 SE), brain death was achieved in 229 s (±9.18 SE), and cardiac arrest occurred in 420 s (±13.57 SE). Time of cardiac arrest differed significantly among stock people when either body weight (BW: P=0.0053) or body mass index (BMI: P=0.0059) was used as a covariate. The BMI was inversely related to the duration of CC (P=0.0227). Moderate to severe hemorrhage severity was reported in 9 of 10 piglets. There was no relationship between FD and BW (P=0.8408) or BMI (P=0.6439). Macroscopic analyses indicated moderate to severe hemorrhage and SK in all piglets. No differences were found among brain sections for SDH (P=0.2302); PH was greater in the cerebral cortex than in the midbrain and brainstem (P=0.0328). The Zephyr-E NPCB reliably caused immediate, sustained insensibility followed by death in neonatal piglets. Postmortem assessment confirmed that application of the Zephyr-E caused widespread, irreversible brain damage.