Abstract
A high prevalence of deviations and fractures of the keel bone is a widespread welfare problem in laying hens. The aim of this study was to experimentally investigate this multifactorial problem throughout the laying period and to compare the prevalence and severity in different layer lines and different housing systems. High performing white (WLA) and brown (BLA) pure bred layer lines and low performing white (R11, G11) and brown layer lines (L68) were kept in both single cages and a floor housing system. A total of 97 hens (19 or 20 from each line, respectively) were repeatedly radiographed in the 35th, 51st and 72nd week of age. Fracture prevalence increased with age (p<0.001). The proportion of deviated keel bone area increased only for caged BLA, WLA and R11 hens (p<0.05) and was significantly higher for caged WLA and R11 hens compared to floor-housed WLA and R11 hens in the 72nd week of age (p<0.05). In the 72nd week of age hens in the floor housing system showed significantly more fractures than hens kept in cages (p<0.05). Prevalence of keel bone deviations was significantly higher in the white layer line R11 but significantly lower in the white layer line G11 compared to both brown layer lines and WLA (p<0.05). Brown layers showed significantly more fractures than white layers (p<0.05) in the 51st and 72nd week of age. Within the brown layers there was a significantly lower prevalence of deviations (p<0.05) and fractures (p<0.05) in the low performing (L68) compared to the high performing line (BLA). Our results show a different development of keel bone damage in caged compared to floor-housed hens under experimental conditions. Additionally, they indicate genetic effects on keel bone damage.
Highlights
Keel bone fractures are one of the most serious animal welfare problems in the egg production industry [1,2,3]
We examined five different pure bred lines of laying hens (Gallus gallus domesticus): three closely related white layer lines (WLA, R11, G11) and two closely related brown layer lines
In contrast, proportion of deviated keel bone area (POD) was significantly higher in the 72nd compared to the 35th week of age in BLA, WLA (35th week of age: 1.84% < 3.09% < 5.19%; 72nd week of age: 5.75% < 9.65% < 16.19%; p
Summary
Keel bone fractures are one of the most serious animal welfare problems in the egg production industry [1,2,3]. Radiographic examination of keel bone damage in laying hens. Beside broken keel bones there is a high prevalence of deviated keel bones. These have been described by CaseyTrott et al [11] as “bone[s] with an abnormally shaped structure that has not resulted from a fracture but contains section(s) that vary from a theoretically perfect 2-dimensional straight plane in either the transverse or sagittal planes. Indentations along the ventral surface can be classified as a deviation.” Reported percentages of keel bone deviations range from 2.6% to 82% [12, 13]
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