Abstract
Keel bone fractures and deviations are one of the major welfare and health issues in commercial laying hens. In non-cage housing systems like aviaries, falls and collisions with perches and other parts of the housing system are assumed to be one of the main causes for the high incidence of keel bone damage. The objectives of this study were to investigate the effectiveness of a soft perch material to reduce keel bone fractures and deviations in white (Dekalb White) and brown laying hens (ISA Brown) kept in an aviary system under commercial conditions. In half of 20 pens, all hard, metal perches were covered with a soft polyurethane material. Palpation of 20 hens per pen was conducted at 18, 21, 23, 30, 38, 44 and 64 weeks of age. Production data including egg laying rate, floor eggs, mortality and feed consumption were collected over the whole laying period. Feather condition and body mass was assessed twice per laying period. The results revealed that pens with soft perches had a reduced number of keel bone fractures and deviations. Also, an interaction between hybrid and age indicated that the ISA hybrid had more fractured keel bones and fewer non-damaged keel bones compared with the DW hybrid at 18 weeks of age, a response that was reversed at the end of the experiment. This is the first study providing evidence for the effectiveness of a soft perch material within a commercial setting. Due to its compressible material soft perches are likely to absorb kinetic energy occurring during collisions and increase the spread of pressure on the keel bone during perching, providing a mechanism to reduce keel bone fractures and deviations, respectively. In combination with genetic selection for more resilient bones and new housing design, perch material is a promising tool to reduce keel bone damage in commercial systems.
Highlights
Keel bone damage— bone fractures and bone deviations—is a major welfare problem in commercial laying hens and possibly the greatest welfare issue egg production is currently facing [1,2]
In terms of housing design, the shift away from battery cages (Switzerland in 1992, EU in 2012) to alternative housing systems such as aviaries allows for greater freedom to move and fly, which likely leads to a higher incidence of keel bone fractures due to high energy collisions in these systems [9]
The first analysis of palpation data focusing on overall keel bone damage (damaged (FK/DK) vs. non-damaged keel bone (NK)) revealed that pens with soft perches had a greater percentage of birds with non-damaged keel bones (Z = 7.06, p< 0.0001; averaged percentage of non-damaged keel bones for entire experiment: soft 55.1% vs. hard 39.8%)
Summary
Keel bone damage— bone fractures and bone deviations—is a major welfare problem in commercial laying hens and possibly the greatest welfare issue egg production is currently facing [1,2]. Causes for keel bone damage are assumed to originate from two factors: 1) genetic selection for increased egg production and 2) inappropriate housing design [6]. In terms of housing design, the shift away from battery cages (Switzerland in 1992, EU in 2012) to alternative housing systems such as aviaries allows for greater freedom to move and fly, which likely leads to a higher incidence of keel bone fractures due to high energy collisions in these systems [9]. The two categories of keel bone damage—fractures and deviations—likely have different prevalence and origins: fractures are assumed to be caused by short-term, high energetic impacts, which occur during collisions with perches or other housing structures [10]. Whether soft perches reduce keel bone damage within commercial systems has not been investigated yet
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