Growing consumer demand for animal welfare and environmental sustainability in the poultry industry is driving the adoption of outdoor access for broiler chickens in the United States. However, shifting to outdoor access from conventional housing may pose tradeoffs for animal welfare, meat quality, and food safety. Research comparing conventional and outdoor access housing on these attributes has not been reviewed for approximately a decade. We reviewed and compared animal welfare, food safety, and meat quality outcomes in conventional versus outdoor access broiler production, focusing on recent research. Despite the prevailing notion that outdoor access improves animal welfare due to more behavioral opportunities, the utilization of the range is highly variable and affected by a variety of environmental, management, and bird characteristics. Outdoor areas containing vegetation and tree cover promote use by the birds, and slow-growing breeds appear to be best suited for these production systems. Typically, welfare-related health outcomes (i.e., footpad dermatitis, mortality, and lameness) are improved with outdoor access. However, birds with outdoor access are at a higher risk for endo- and ectoparasitic infections. Antimicrobial resistance is typically lower on outdoor access farms, and birds with outdoor access have more diverse microbiomes. There are mixed results for the prevalences of Salmonella and Campylobacter between conventional and outdoor access farms. Meat quality varies in complex ways related to rearing system, age, breed, diet, and behavior. Meat from outdoor access broilers may present better taste or flavor, yet there can be tradeoffs for texture and moisture, particularly for older, slower-growing breeds that are typical of outdoor access production. Taken together, studies to date indicate multiple benefits and tradeoffs for animal welfare, food safety, and meat quality. Variations in management between farms and certification criteria result in inconsistent outcomes. The majority of outdoor access research has been conducted outside of the United States. Region-specific research accounting for geography, climate, and available breeds would be beneficial for improving outdoor access production outcomes in the United States.

The skeletal health of laying hens improves when birds are given opportunities to perform load-bearing movements with elevated structures, such as perches. We investigated how early access to elevated structures varying in complexity and height would affect bone quality and subsequent keel bone fractures in a layer multitiered aviary. Female Dekalb White pullets were reared in floor pens furnished with floor perches (FL), single-tiered aviaries (ST), or 2-tiered aviaries (TT; n = 5 pens/treatment) through 16 wk of age. At 17 wks, all structures were replaced with identical multitiered layer aviaries. The keel, both tibiae, and both humeri were collected from 60 euthanized birds from each rearing treatment at 8, 16 and 30 wk of age, and analyzed with dual X-ray absorptiometry (DEXA) for bone mineral density and length. At 18, 26, 28, and 30 wk of age, 10 focal hens/pen were radiographed repeatedly and the presence, severity of keel bone fractures were assessed with a tagged visual analogue scale. The number of fractures was also recorded. At 16 wk of age, FL pullets had lower BMD of the tibia (P = 0.003), keel (P = 0.013), and humerus (P = 0.004) compared to ST and TT pullets. Most of the observed treatment differences disappeared after pullets were transferred to the aviary. BMD continued to increase for all hens through 30 wk of age. Pullet rearing did not affect the presence or severity of keel bone fractures, or number of new fractures incurred between ages (P > 0.05). The prevalence and severity of keel bone fractures increased between 26 to 28 wk and remained high to 30 wk of age (P < 0.0001). Hens experienced more new fractures between 26 to 30 wk than between 18 to 26 wk of age (P = 0.0046). The effects of pullet housing on bone quality were short-term when hens had access to adult housing with multiple opportunities for load-bearing movements. Keel fractures with minor severity were high in prevalence reflecting the use of radiography to assess this injury.

Euthanasia is an essential task performed daily on commercial poultry farms around the world to safeguard animal welfare. Manual cervical dislocation (MCD) is the most common euthanasia method but can be challenging to perform given the physical strength required to implement this technique. Therefore, the objective of this study was to evaluate the efficacy of a novel cervical dislocation tool (NCDT) compared to MCD. A total of 60 Ross 308 chickens (6-wk old) and 60 Ross 706 parent stock breeders (21-wk old) were enrolled in the study. Birds were sexed, blocked by body weight, and allocated to 1 of 2 treatments: 1) MCD and 2) NCDT. Immediately following euthanasia application, insensibility, and death were monitored. Once death was confirmed, gross evaluation, radiograph, and macroscopic/microscopic scoring were performed. Both euthanasia methods were 100% effective in achieving insensibility followed by cardiac and respiratory arrest in both age groups. In 6-wk-old broilers, there were no differences in insensibility measures or location and severity of the dislocation site by treatment. The NCDT treatment group showed an increased frequency of fractures located at the tooth-like process that projects from the cranial aspect of the centrum of the axis (dens) but had no impact on bird insensibility. For parent stock, differences in nictitating membrane reflex (NMR) and laceration scores for birds euthanized with NCDT were found and likely associated with additional force exerted with the tool. The NCDT is a promising replacement for MCD and future work should address the development of free and accessible training materials for on-farm use.

Spatial abilities of hens are particularly sensitive to development during early life. Experiences in pullet housing may have lasting consequences on adult hens' movements in cage-free environments. We tested whether opportunities to access elevated spaces during rearing improved hens' use of a multitiered aviary. Female Dekalb White pullets were reared in either floor pens (FL), single-tiered aviaries (ST), or 2-tiered aviaries (TT; n = 5 pens/environment) through 16 wk of age. Rearing structures were replaced with identical multitiered aviaries at 17 wk. The distribution of the flock within the aviary and the vertical transitions of 10 focal hens/pen across the aviary were determined from videos recorded during their first (D1) and seventh (D7) day of aviary access, as well as at 19, 23, and 27 wk of age. Prevalence of floor eggs was recorded weekly from 17 to 28 wk of age. On D1, more ST and TT hens utilized the aviary during the daytime (P = 0.0077), made more vertical transitions when searching for a roosting spot in the evening (P = 0.0021), and maintained a consistent distance traveled during transitions compared to FL hens (P = 0.02). These differences disappeared by D7, except that ST and TT hens continued to roost on the highest perches of the aviary more (P < 0.0001) than FL hens through 27 wk of age. FL hens laid more floor eggs than ST and TT hens for the first 2 wk of lay (P < 0.0001). The majority (97.9%) of vertical transitions was controlled. Uncontrolled transitions were highest at D1 and decreased by D7 (P = 0.0009) and were not affected by rearing (P = 0.33). The results suggest that hens reared with minimal height are hesitant to use the laying hen aviaries when they are first transferred. They acclimate within 1 to 2 wk, but continue to roost less in the highest accessible level.

Multi-tiered aviary systems provide laying hens with opportunities for species-specific behaviors, including vertical and horizontal movement. However, collisions and failed landings that occur during vertical movement can be associated with injuries. Previous studies suggest that floor rearing of pullets with minimal access to elevated structures may negatively impact adult laying hens' ability to navigate vertical space. However, it is not clear whether this is due to deficits in physical ability or differences in depth perception. This was investigated in pullets and egg-laying hens using a modified Y-maze task and a visual cliff task at 7-8, 15-16, and 29-30 weeks of age. Dekalb White pullets (N = 450) were reared in three different environments until 16 weeks of age: floor, single-tier aviary, and two-tier aviary. From 16 weeks of age, all birds were housed in a multi-tier aviary. The Y -maze task consisted of two arms that were either a ratio of 1:3 or 1:1 in length. Each bird's ability to discriminate the different arm lengths was evaluated based on latency to exit and arm choice. The illusion of depth over a plexiglass floor was tested in the visual cliff task at 15, 30, and 90 cm. Birds were given 1.5 min to either leave the start perch by jumping to a platform suspended over the visual cliff, or step down off the perch to the shallow side. Latency to jump to the platform and frequency of looking down over the visual cliff were recorded. There were no main effects of age or rearing treatment on behavior in the Y-maze, with all birds choosing the shorter arm more than chance (p < 0.001). Regardless of cliff height, birds reared on the floor were less likely to cross the visual cliff at 8 and 16 weeks of age than single and two-tier treatment birds (p = 0.01). However, these dif-ferences were not observed after they were given experience with elevated structures in the adult aviary. The results of the present study suggest that the lack of exposure to vertical complexity during rearing do not cause long-term detriments to depth perception, but could impact successful engagement with elevated heights (i.e., hesitancy to access vertical structures). Further research is needed to determine the timing, quality, and quantity of elevated height exposure that is needed in the rearing environment to encourage sufficient use of vertical space in the adult aviary for cage-free laying hens.

Pullets reared with diverse behavioral experiences are faster to learn spatial cognition tasks and acclimate more successfully to laying environments with elevated structures. However, the neural underpinnings of the improved spatial abilities are unclear. The objective of this study was to determine whether providing structural height in the rearing environment affected the development of the hippocampus and whether hippocampal neural metrics correlated with individual behavior on spatial cognition tasks. Female Dekalb White pullets were reared in a floor pen (FL), single-tiered aviary (ST), or two-tiered aviary (TT; 5 pens/treatment). Pullets completed floor-based Y-maze and elevated visual cliff tasks to evaluate depth perception at 15 and 16 wk, respectively. At 16 wk, brains were removed for Golgi-Cox staining (n = 12 for FL, 13 for ST, 13 total pullets for TT; 2 to 3 pullets/pen) and qPCR to measure gene expression of brain-derived neurotrophic factor (BDNF;n = 10 for FL, 11 for ST, and 9 pullets for TT). Rearing environment did not affect various morphometric outcomes of dendritic arborization, including Sholl profiles; mean dendritic length; sum dendritic length; number of dendrites, terminal tips, or nodes; soma size; or BDNF mRNA expression (P > 0.05). Hippocampal subregion did affect dendritic morphology, with multipolar neurons from the ventral subregion differing in several characteristics from multipolar neurons in the dorsomedial or dorsolateral subregions (P < 0.05). Neural metrics did not correlate with individual differences in behavior during the spatial cognition tasks. Overall, providing height during rearing did not affect dendritic morphology or BDNF at 16 wk of age, but other metrics in the hippocampus or other brain regions warrant further investigation. Additionally, other structural or social components or the role of animal personality are areas of future interest for how rearing environments influence pullet behavior.

Laying hens are susceptible to keel bone fractures due to continuous endogenous calcium resorption for eggshell formation. Although it is assumed that external trauma to the keel bone, e.g., due to collisions, is the main cause for fractures, accumulated forces or asymmetric load on a weakened bone might contribute to the high keel bone fracture prevalence found in commercial laying hens. The objective of this study was to investigate whether forces applied to the keel due to involuntary convulsions and uncontrolled wing flapping during euthanasia have the potential to cause keel bone fractures. Two hundred and seventy Dekalb White laying hens were euthanized at 30 weeks of age using cervical dislocation ( n = 60) or CO 2 ( n = 210). All hens were radiographed immediately before and after euthanasia. Radiographs were compared side by side to detect new fractures. Four out of the 270 hens (1.5%) obtained a fracture during euthanasia. Specifically, 0.95% of hens euthanized with CO 2 (2 out of 210) and 3.3% of hens euthanized through cervical dislocation (2 out of 60) obtained a euthanasia-induced fracture. All four hens with a euthanasia-induced fracture had signs of damage to the keel before euthanasia, indicating that pre-existing fractures could affect fracture susceptibility. Based on our results, we cannot rule out that convulsions during euthanasia can cause keel bone fractures in laying hens. In studies investigating keel bone integrity in birds euthanized with CO 2 or cervical dislocation, fracture prevalence might be overestimated. Future research is needed to assess whether euthanasia might be more likely to cause keel bone fractures in older birds and to quantify the frequency and strength of convulsions as a potential cause of fractures.

Hens reared in aviaries (AVI) as pullets have improved spatial abilities compared to hens reared in non-enriched cages (CON). However, this effect on behavior has been shown only to 23 weeks of age. Lohmann LSL-Lite hens were reared in either CON or AVI until 19 weeks of age and then moved into enriched colony cages (ECC) containing two elevated perches of different heights (n = 6 ECC/treatment). Focal hens (3 per ECC) were fitted with tri-axial accelerometers to record acceleration events at 21, 35, and 49 weeks of age. Video recordings from each age were used to identify behaviors associated with acceleration events as well as the proportion of hens utilizing perches. CON hens experienced more acceleration events (p = 0.008) and more collisions (p = 0.04) than AVI hens during the day at 21 and 35 weeks of age. The total proportion of hens perching at night was similar between treatments across most time points, but fewer CON hens used the high perch compared to AVI hens throughout the study (p = < 0.001). Rearing in aviaries influences hen behavior out to peak lay for collisions and out to mid-lay for perch height preference in ECC.

The study of farm animal behaviour is a critical tool for assessing animal welfare. Collecting behavioural data with continuous sampling or short scan sampling intervals (eg every 60th second) is considered ideal as this provides the most complete and accurate dataset; however, these methods are also time and labour intensive. Longer sampling intervals provide an alternative in order to increase efficiency, but these require validation to ensure accurate estimation of the data. This study aims to validate scan sampling intervals for lambs (Ovis aries) housed on pasture. Grazing, lying, standing, drinking, locomotion, and mineral consumption were evaluated from six pens of crossbred lambs (six lambs per pen) for 15 h. Data from 1-min instantaneous scan sampling were compared with data from instantaneous scan sampling intervals of 5, 10, 15, and 20 min in two statistical tests: generalised linear mixed model and regression analysis. Using the mixed model, the percentage of time each behaviour was performed did not differ amongst sampling intervals for all behaviours except grazing, which was statistically different at 20-min intervals. Using regression analysis, lying and grazing estimations were accurate up to 20-min intervals, and standing was accurate at 10and 20-min intervals only. Locomotion, mineral consumption, and drinking demonstrated poor associations for all tested intervals. The results from this study suggest that a 10-min instantaneous scan sampling interval will accurately estimate lying, grazing, and standing behaviour for lambs on pasture. This validation will assist with the efficiency of future data collection in lamb behaviour and welfare research.

Two experiments were conducted to determine the effects of weaning age on lamb growth and the severity of parasitic infection in grazing lambs. All lambs were fed in a feedlot until they reached a set marketable weight after their allocated grazing period. In experiment 1, 48 Hampshire x Dorset and Suffolk x Dorset crossbred lambs and 24 Dorset x Suffolk and Dorset x Hampshire crossbred ewes were placed into one of two weaning treatments for 63 days: Pasture control (PC): lambs weaned early at 60 days of age and placed on pasture and Ewe (E): Lambs placed on pasture at 60 days of age with ewe and weaned at approximately 123 days of age. The E lambs had a greater average final body weight, total ADG, and PCV value on day 63 compared to PC lambs during the grazing period (P < 0.05). In the feedlot, E lambs spent fewer days in the feedlot to reach market weight and had a greater overall ADG with PC lambs demonstrating a greater G:F and total DMI (P < 0.05). In experiment 2, a total of 72 crossbred lambs and 27 crossbred ewes were placed into one of four weaning treatments for 56 days: Pasture control (PC). Ewe (E): Iambs weaned at approximately 116 days of age. Social facilitator (SF): lambs weaned at 60 days of age and placed on pasture with non-lactating, non-related ewes. Feedlot control (FC): lambs weaned at 60 days of age and placed in a research feedlot facility. Feedlot control lambs were not re-exposed to parasites after the initiation of the experiment and therefore included as an industry standard control. The E lambs demonstrated greater BW from day 42 to the end of the grazing period and FC lambs had the lowest BW from day 7 to day 28 and a greater ADG on day 56 of the grazing period (P < 0.05). The E and FC lambs also demonstrated a smaller difference in change in PCV values from day 28 to the end of the grazing period (P < 0.05). In the feedlot, E lambs required less total weight gain and had lower DMI compared to all other treatments to reach market weight (P < 0.05). The FC lambs had a greater total weight gain, DMI, and G:F compared to all other treatments (P < 0.05). The results from these two experiments demonstrate that extending the weaning age of lambs beyond 60 days of age in pasture-based systems can be beneficial from an animal health standpoint and requires less harvested grain in the feedlot to reach a market appropriate endpoint.

When considering methodologies for collecting behavioral data, continuous sampling provides the most complete and accurate data set whereas instantaneous sampling can provide similar results and also increase the efficiency of data collection. However, instantaneous time intervals require validation to ensure accurate estimation of the data. Therefore, the objective of this study was to validate scan sampling intervals for lambs housed in a feedlot environment. Feeding, lying, standing, drinking, locomotion, and oral manipulation were measured on 18 crossbred lambs housed in an indoor feedlot facility for 14 h (0600-2000 h). Data from continuous sampling were compared with data from instantaneous scan sampling intervals of 5, 10, 15, and 20 min using a linear regression analysis. Three criteria determined if a time interval accurately estimated behaviors: 1) ≥ 0.90, 2) slope not statistically different from 1 ( > 0.05), and 3) intercept not statistically different from 0 ( > 0.05). Estimations for lying behavior were accurate up to 20-min intervals, whereas feeding and standing behaviors were accurate only at 5-min intervals (i.e., met all 3 regression criteria). Drinking, locomotion, and oral manipulation demonstrated poor associations () for all tested intervals. The results from this study suggest that a 5-min instantaneous sampling interval will accurately estimate lying, feeding, and standing behaviors for lambs housed in a feedlot, whereas continuous sampling is recommended for the remaining behaviors. This methodology will contribute toward the efficiency, accuracy, and transparency of future behavioral data collection in lamb behavior research.

Lambs are commonly weaned around 60 d of age in the Eastern United States, but this age is also a time for lambs to apply long-term feeding strategies learned from adult animals. There is minimal evidence on how weaning strategies may affect long-term adaptation of feeding behavior. The objective of this study was to assess the effect of social and environmental factors at weaning on short- (3 d post-weaning) and long-term (8 wk post weaning) feeding, lying, and standing idle behavior of lambs on pasture or in a feedlot. Two experiments tested this objective: Experiment 1 investigated social dynamics at time of weaning for lambs housed on pasture, and Experiment 2 investigated the effect of weaning into a feedlot compared to a pasture environment. At 60 d of age, 72 crossbred twin lambs were assigned to one of four treatments: lambs weaned and placed with similar aged lambs onto pasture (W); lambs weaned and placed with similar-aged lambs and non-related adult ewes onto pasture (SF); lambs that remained with their dam on pasture (E); and lambs weaned and placed with similar aged lambs into a feedlot (FL). Each treatment had three replicates with six lambs/replicate. Behavioral data were collected with instantaneous scan sampling for 15 h/d for 55 d. During the first 3 d after weaning in Experiment 1, W lambs spent more time standing than SF lambs (P = 0.03), and all lambs decreased standing idle time over the 3 d (P < 0.0001). During the 8 wks after weaning, W and SF lambs spent more time grazing (P = 0.03) and less time lying (P = 0.02) compared to E lambs. In Experiment 2, feeding time of FL lambs increased on d 3 compared to d 1 and 2 (P < 0.05). However, there was no effect of week on feeding, lying, or standing time over the long-term period (P > 0.05). When the time-budgets of lambs from both experiments were compared, W lambs spent 39.2% more time grazing compared to the amount of time that FL lambs spent feeding. Results suggest that keeping non-related adult ewes (SF) with weaned lambs did not influence the grazing and lying behavior of lambs on pasture. Lambs that stayed with their dams and were weaned later (E) had the lowest grazing time, likely because they are still receiving milk. Lambs in the feedlot environment increased their time spent feeding in the first few days, suggesting an initial adaptation to stress after weaning.