Comparisons of bone properties and keel deformities between strains and housing systems in end-of-lay hens

Abstract

Susceptibility of caged layers to osteoporosis and cage layer fatigue has generated interest in newer housing systems that favor increased load-bearing activities. However, high incidences of fractures incurred during lay period have been reported in these newer systems. This study is aimed at determining the housing and strain effects on bone properties: dry weight, percentage ash content, cortical density (CBD), cortical thickness (CBT), and keel bone deformities. Tibia, femur, and keel from Hy-Line Brown (HB), Hy-Line Silver Brown (SB), and Barred Plymouth Rock (BR) hens housed in conventional cages (CC), cage-free (CF), and cage-free with range (outdoor access; R) were studied. At 78 wk, 60 hens from each strain and housing system combination were euthanized and bones were excised for analysis. Quantitative computed tomography (QCT) was used to measure CBD and CBT in each bone. Three-dimensional images of keels were generated from software using QCT scans to analyze the deformities. Tibiae CBT was greater (P < 0.01) in BR compared to other two strains. Between housing systems, CBT was greater (P < 0.05) for mid and distal tibia of R and CF compared to CC. Tibiae and femoral cortex were denser (P < 0.05) in BR compared to HB and SB. There was no effect of housing system for femur CBD, but CBD was greater (P < 0.05) for middle and distal tibia of birds housed in R compared to CC. CBD for keel bone was greater (P < 0.05) in CF and R birds compared to CC birds. The housing system did not influence the dry bone weight and ash percentage of tibiae and femur. Each housing system was associated with high prevalence (>90%) of keel deformities and the housing and genotype influenced the type of deformity. These findings indicate that range and cage-free housing may have beneficial impact on tibia and keel bone integrity compared to conventional cages but the improvement may not be sufficient to prevent fractures or deformities of keel.

Pathological characterization of keel bone fractures in laying hens does not support external trauma as the underlying cause

“…Predisposing factors have also been suggested including genetics of the bird, lack of specific feedstuff components, high egg production. Layer fatigue or poor bone health have also been suggested to be contributing factors [25,27,28].…”

Keel bone damage in laying hens reared in different production systems in Serbia

“…During the last decade, numerous studies, done mostly in the EU countries, have documented fractures and deformation of the keel bone in laying hens, which range between 5% and 97%, depending on the housing system and hen age (Rodenburg et al, 2008;Wilkins et al, 2011;Petrik et al, 2015;Riber and Hinrichsen, 2016;Regmi et al, 2016). So far, no similar research was conducted in our country.…”

Reproductive management of poultry

“…110 Moreover, there was a greater incidence of keel deformities in hens in a cage free system compared to those in conventional cages. 111 There are also differences in leg bone characteristics with hens under the cage free conditions having increased cortical cross-sectional area and cortical density of their humerus and tibia compared to those maintained in conventional cages. 112 Moreover, there was there was greater stiffness of both humerus and tibia and increased percentage ash in the humerus in hens in a cage free system.…”

“…112,113 However, in another study, there were little differences between tibia and humerus parameters between hens in cage-free or conventional cage systems. 111 In laying hens at the end of the laying cycle, there were differences in bone characteristics depending on the environment under which the pullets were raised. 112 Production has been compared between Lohmann Brown layer hens in convention layer housing, enriched convention layer housing and free-range systems.…”