Abstract
ABSTRACTThe present study aimed to investigate the effect of three housing systems (furnished cages – FC, barns – B, and free-range – FR) on the prevalence and severity of keel bone protrusion and deformations. These health and welfare indicators were measured at the slaughterhouse, using a 4-point scale (0 = absence, 1 = slight, 2 = moderate and 3 = severe). Keel bone deformation was also categorized in relation to the presence of compression over the ventral surface, deviation from a 2D straight plane and deviation from the transverse (C-shaped) or median sagittal (S-shaped) plane. The housing system had a significant effect on prevalence of keel bone deformation (χ2 = 45.465, df = 6, P < 0.001). In FR systems 60.4% of hens presented keel bone deformation, followed by 54.2% in FC and 53.5% in B; however, higher scores for keel bone deformations were more frequent in B systems. Although keel bone protrusion was observed in all laying hen systems, the majority of hens only presented a slight degree (score 1) of protrusion. A positive correlation was obtained for keel bone protrusion and emaciation. The results could be used to initiate detailed investigations into problematic issues that occur during the laying period to improve the health and welfare conditions on farms.
Highlights
The keel bone is an extension of the ventral surface of the sternum, progressing along the midline of the sagittal plane
The present study aimed to investigate the effect of three housing systems
The frequencies of keel bone deformations differed between the housing systems (χ2 = 45.465, df = 6, P < 0.001)
Summary
The keel bone is an extension of the ventral surface of the sternum, progressing along the midline of the sagittal plane. It is important to the successful daily function of birds, in both flight and respiratory efficiency (Claessens, 2009). Due to their genetic selection for high egg production, laying hens are at risk of rapid depletion of body reserves. The modern breast conformation of laying hens with a prominent keel bone may be a predisposition factor for its damage (Fleming et al, 2004; Sherwin et al, 2010). Gregory and Robins (1998) demonstrated that scoring the body condition of hens, according to the keel protuberance and breast muscle size, was well correlated with fat and muscle development. Visual assessment of the body condition directly in the slaughter line is straightforward and it is regularly used during meat inspection for condemnation of emaciated carcasses (Graft et al, 2017)
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