Laying hen skeletal health continues to be an industry priority. Bone ash and bone Ca quantification in laying hen long bones provides valuable infor

Keel bone damage, which presents as fractures and/or deviations of the keel, has been detected in laying hens housed in all types of systems. Factors leading to keel bone damage in hens housed with limited vertical space, such as those housed in furnished systems, are not well understood, and are the topic of this study. Ten focal hens from each of 12 furnished cages (4 rooms of 3 cages) were fitted with keel mounted tri-axial accelerometers. Their behavior was video recorded continuously over two 3-wk trials: the first when the hens were between 52 and 60 wk of age, and the second approximately 20 wk later. The integrity of each hen's keel was evaluated at the start and end of each 3-wk trial using digital computed tomography. We identified predominant behaviors associated with acceleration events sustained at the keel (collisions, aggressive interactions and grooming) by pairing accelerometer outputs with video data. For each recorded acceleration event we calculated the acceleration magnitudes as the maximum summed acceleration recorded during the event, and by calculating the area under the acceleration curve. A principle components analysis, which was used as a data reduction technique, resulted in the identification of 4 components that were used in a subsequent regression analysis. A key finding is that the number of collisions a hen has with structures in her environment, and the number of aggressive interactions that a hen is involved, each affect the likelihood that she will develop 1 or more fractures within a 3-wk time span. This relationship between hen behavior and keel fracture formation was independent of the magnitude of acceleration involved in the event. Observed behavior did not have an impact on the formation of keel bone deviations, further supporting reports that the mechanisms underlying the 2 types of keel bone damage are different.

The global egg industry is rapidly transitioning to cage-free egg production from conventional cages. Hens housed in cage-free systems have an increased prevalence of keel damage that could lead to reduced egg production and compromised well-being. The objective of this study was to determine the effects of dietary supplementation of n-3 fatty acids and vitamin D₃ on keel damage in hens housed in multi-tier aviary systems (AV). Brown hens were placed in 4 AV system rooms after rearing at 17 wk of age (woa) with each room containing 576 birds. At 12 woa, rooms were randomly assigned to a dietary treatment of flaxseed oil, fish oil, vitamin D₃, or control. Focal birds (36 per treatment) were longitudinally examined for keel damage using quantitative computed tomography (QCT) at nine timepoints from 16 to 52 woa. Three-dimensional digital twins of the keels were created from the QCT scans and visually assessed for damage. An overall keel severity score was recorded as well as the location, direction, and severity of each deviation or fracture. Severity was ranked on a 0 to 5 scale with 0 being no damage and 5 being severe. Damage scores were analyzed utilizing odds ratios with main effects of age and treatment. At 16 woa, 80% of hens had overall keel scores of 0 and 20% had scores of 1. At 52 woa, all hens had damage, with 31% having a score of 1, 61% scored 2 to 3, and 8% scored 4 to 5. Most fractures were not observed until peak lay. Dietary treatments did not affect likelihood of fracture incidences, but younger birds had lower odds of incurring keel fractures than older birds (P < 0.0001). The initial incidences of keel deviations occurred earlier than fractures, with most birds obtaining a keel deviation by 28 woa. Keel damage was not able to be prevented, but the age at which keel fractures and deviations initiate appear to be different, with deviations occurring during growth and fractures during lay.

Management choices during the pullet phase can affect behavior, welfare, and health later in life, but few studies have evaluated the pullet phase, particularly in extensive housing systems. This study was a 2 × 2 factorial randomized complete block design (RCBD) with two strains and two stocking densities. The Lohmann LB-Lite and Lohmann LSL-Lite were housed on the floor at high-stocking density (619–670 cm²/bird) and low-stocking density (1249–1352 cm²/bird), which changed with age from 2 to 16 weeks of age (WOA). Bird-based measures of appearance, blood parameters, organ measurements, and production values were evaluated. Stocking density alone affected (p < 0.05) only relative bursal weight (% of body weight)—3.32% in the low-density versus 3.08% in the high-density group. High-stocking density was correlated with decreased uniformity (high—89.33 ± 0.24%; low—90.41 ± 0.24; p < 0.02) and worse feather coverage in the brown strain. High-stocking density was correlated with greater uniformity (High—90.39 ± 0.24%; Low—88.47 ± 0.24%; p < 0.001) and better feather coverage in the white strain. This study’s feed conversion ratio (FCR) was improved by 0.07 in the low-stocking density for both strains. The remaining parameters were affected by strain and age only. Thus, while stocking density effects vary slightly depending on the strain used, cage-free pullets had limited negative effects at both the high and low-stocking densities tested in this study; there were few to no changes in the numerous bird-based welfare parameters tested.

Keel bone fractures and osteoporosis are prevalent and damaging skeletal issues in the laying hen industry. There is a large interest in improving bone quality parameters to reduce or eliminate these conditions, thus improving bird welfare. Both essential fatty acids (EFA) and vitamin D can play a role in bone metabolism. The hypothesis of this study was that birds supplemented with lower n-6:n-3 EFA ratio or vitamin D would have improved bone properties compared to a control diet. A total of 3,520 Lohmann Brown-Lite pullets were used in this study. Pullets were housed on the floor from 0 to 17 wk of age and then moved to an aviary (17-52 wk of age). Starting at 12 wk of age, birds were split into diet treatments-control, flax, fish, or vitamin D diets with n-6:n-3 ratios of 6.750, 0.534, 0.534, and 6.750, respectively. Diets were formulated to be isonitrogenous and isocaloric. Basal vitamin D3 levels were formulated to be 2,760 IU/kg across all diets; for the vitamin D diet, the vitamin D3 level was increased to 5,520 IU/kg. Hens on fish and vitamin D diets had greater bone density, keel bone volume, digital bone mineral content, and keel condition compared to flax and control hens. Additionally, birds fed the vitamin D diet had the heaviest body weights compared to birds fed fish or control diets. Birds fed the flax and vitamin D diets had improved feather coverage across multiple body regions. Feeding an n-3 EFA- or vitamin D-enriched diet decreased mortality by 1.6 to 3.3% compared to the control. The fish and vitamin D diets generated mixed production performance. Compared to the other treatments, the vitamin D diet generated higher case weights but lower hen day percentage throughout the study. When compared to the other treatments, the fish diet had the lowest case weights but had a greater hen day percentage after 36 wk of age. Results indicate that a fish-based EFA and vitamin D supplementation show promise in improving skeletal health but require further investigation.