Title: Effect of pullet rearing environment, strain and perch shape on perching behaviour, perching biomechanics, and keel bone damage in enriched-housed laying hens
Authors: Emily DePaoli, Dr. Doug Korver, Dr. Clover Bench
SUMMARY
ABOUT
As the Canadian laying hen industry shifts towards alternative housing systems (furnished cages, aviary, free-run, and free range) keel bone damage (KBD) has been identified as a welfare concern. Keel bone fractures lead to reduced egg production and negative affective states due to pain. Perches in alternative systems increase the incidence of KBD by 24–54% in comparison to conventional cages. Wider perches (e.g., mushroom or rectangular) distribute the force exerted on the keel by increasing the contact area between the perch and keel which reduces KBD severity. Exploring the effects of perch shape in furnished cage systems could help reduce the incidence of KBD below the 20% average in conventionally housed flocks. Pullet rearing environment and laying hen strain can also impact the incidence and severity of KBD. Non-cage rearing systems provide opportunities for load-bearing exercise leading to higher bone mineral content. Opportunities for exercise allow for increased medullary bone deposition and bone mineralization. The objectives of the current study were to determine if perching biomechanics lead to stability and, in turn, reduced keel bone damage and how perch shape (mushroom vs round), strain (Lohmann White vs Lohmann Brown), and pullet rearing environment (floor pen vs pullet cage) impacted perching biomechanics and KBD.
APPROACH
This study used a 2×2 randomized complete block design with repeated measures. Two commercial egg-laying strains, Lohmann White (LW; n=360) and Lohmann Brown (LB; n=360) were evaluated. At 17 weeks of age, all birds were moved into a Tecno Plus battery containing nest curtains, a scratchpad, two perches (64 cm×3.5 cm×6 cm), a water line, and a feed trough. The battery consisted of 72 cages (10 birds per cage) and three tiers, treatments were balanced for side, tier level, and end vs middle positions along the battery. Perch shape was kept identical during pullet rearing and the laying phase across treatments. Birds housed in cages during pullet rearing were kept together in the laying phase, while birds housed in floor pens were sorted evenly into cages based on treatment. Laying hens were provided with either a round or mushroom shaped perch and housed in either a pullet cage or floor pen. Throughout lay, all hens were housed in furnished cages with nine replications of each treatment combination. There were eight floor pens (2.3 m by 5.5 m) divided into two perch shape treatments (mushroom and round) with 45 birds per pen (0.28 m2/pullet). There were 36 cages (53.3 cm×25 cm x 119.4 cm) divided into two perch shape treatments (mushroom and round) with 10 birds per cage (128 cm2/pullet). Birds were housed to 70 weeks of age. Body weights were measured at 2, 4, 6, 8, 10, 12, 14, and 16 months of age. From seven weeks of age to 69 weeks of age, behaviour observations occurred. Dual X-Ray Absorptiometry (DXA) was used to determine bone mineral content and density. Radiographic bone mineral density and content measurements of the dissected and cleaned keel and left femur were analyzed post-mortem at 70 weeks of age utilizing LUNAR Prodigy DXA. At 4, 6, 8, 10, 12, 14, and 16 months of age all focal birds were assessed via manual palpation for presence of fractures on the ventral surface of the keel, severity of deviations and body condition score.
ANALYSIS OF RESULTS
Lohmann Browns were 1.63–6.90 times more likely to perch during peak lay and 3.28–5.36 times more likely to perch during end of lay than LW. At the end of lay, laying hens were 1.23–1.45 times more likely to perch on mushroom perches than round perches (P<0.001 to P<0.05). During peak lay, laying hens reared in cages were 1.33–1.84 times more likely to perch than those reared in floor pens except at 25 and 31 weeks of age (P<0.05 to P<0.001). During peak and end of lay, laying hens housed in cages were 0.8–0.83 times less likely to stand on the perch only 40% of the time (P<0.001 to P<0.05). At 19 and 21 weeks of age LB were 1.22 times more likely to stand on the perch than LW (P<0.05). In contrast, from 27 to 33 weeks of age, LB were 0.58–0.74 times less likely to stand on the perch than LW (P<0.001). At 65 and 67 weeks of age LB were 1.25–1.32 times more likely to stand on the perch than LW (P<0.001 to P<0.05). During peak of lay, laying hens were 0.2–0.46 times less likely to stand on mushroom perches compared to round perches and 0.31–0.47 times less likely to stand on mushroom perches compared to round perches at end of lay (P<0.001 to P<0.05). Lohmann Brown pullets reared in floor pens had a higher incidence of perching than LW pullets, independent of the type of perch. In contrast, LB pullets reared in cages had a lower incidence of perching but a higher incidence of standing on the round perch than LW pullets. Lohmann Brown was more likely to have more fractures than Lohmann White (P<0.01). Pullet rearing environment, perch shape and body weight, in contrast, did not significantly impact the bone parameters measured (P>0.10).
APPLICATION
In conclusion, strain, perch shape, and pullet rearing environment significantly impacted perching biomechanics. Lohmann Whites moved faster and had the lowest incidences of severe keel bone damage. In addition, mushroom perches led to less severe KBD and were preferred by laying hens at peak and end of lay. Lohmann Brown had significantly stronger and denser bones than LW, while the pullet rearing environment did not significantly impact the bone parameters measured. Higher bone density and strength were not protective against keel bone damage. Based on the incidence of KBD, Lohmann White may be more suited to furnished cage housing in comparison to LB. Future research utilizing 3D kinematics technology in poultry could investigate the provision of perches during the pullet rearing phase on the development of perching behaviour.
Read the full article at https://doi.org/10.1016/j.applanim.2024.106187
Thania joined PIP as the PIP Extension technician in 2021.
