Soft Perches in an Aviary System Reduce Incidence of Keel Bone Damage in Laying Hens

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.

The Role of Egg Production in the Etiology of Keel Bone Damage in Laying Hens

“…Body weight is discussed to affect the occurrence of keel bone fractures and deviations. On the one hand, it is assumed that higher body weight may increase the risk of keel bone fracture due to greater collision energies when colliding with a perch (5,15). On the other hand, it is possible that a higher breast muscle mass, which also increases body weight, may have a protective effect on the keel bone because low breast muscle mass leaves the keel vulnerable to fracture (13).…”

“…Additionally, indentations along the ventral surface can also be classified as a deviation" (11), can reach up to 82% (12,13). Age (4,5,(14)(15)(16)(17)(18), different housing systems (4,7,19), nutrition (20)(21)(22), and genetic background (5, 17-19, 23, 24) have been shown to influence KBD. Egg production and the high laying performance of modern laying strains may also favor the occurrence of keel bone damage.…”

“…When investigating keel bone damage in laying hens, it is crucial to observe the same hens over a longer period of time because prevalence of both keel bone fractures and deviations has been shown to increase with age (5,14,(16)(17)(18)(19). However, in some studies, prevalence only increased until about the 50th week of age and then leveled off or even decreased (4,15,21). Although it is possible that this peak in prevalence of fractures and deviations may partly be explained by the decreasing pool of hens that are still fracture and deviation free, it is also possible that the keel bone is less susceptible to damage after a certain age.…”

Associations between and development of welfare indicators in organic layers

“…Keel bone damage is a term covering both keel bone deviations and keel bone fractures. Long-term pressure on the keel bone, especially on poorly designed perches, is one identified factor causing keel bone deviations (Tauson and Abrahamsson, 1994;Pickel et al, 2011), whereas keel bone fractures are likely to be caused by collision with housing equipment or other hens (Freire et al, 2003;Sandilands et al, 2009;Stratmann et al, 2015).…”

Why Pain Is Still a Welfare Issue for Farm Animals, and How Facial Expression Could Be the Answer

“…Changing some of the materials used in animal housing can also have a positive effect on welfare, for example Brscic et al [37], covered concrete slats with a synthetic rubber, reducing the number of beef cattle needing treatment for locomotor problems. Stratmann et al [38] also reduced the number of keel bone fractures in laying hens by adding a polyurethane material around metal perches in an aviary system.…”