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Problem of Keel Fractures and Deformities Evaluated

01/09/2018

In an article* circulated by Lohmann Breeding Company of Germany, Dr. W. Icken and colleagues evaluated the literature concerning keel (sternal) abnormalities including deformation and fractures. The authors considered 16 peer-reviewed articles from 1998 to 2013, documenting keel deformities in various housing systems.

Data was also presented on two breeding lines which demonstrated differences in the prevalence and heritability of keel defects. The study conducted by Lohmann Breeding Company evaluated 5,869 pure hens of two different White Leghorn lines which were scored by palpation at 46 and 70 weeks of age respectively.  Intra-observer reliability for palpation score was high (r = 0.82) in both lines confirming that the evaluation technique was consistent and reproducible.  Heritability was moderate in line A with a 75 percent prevalence of deviations (h2= 0.30). In line B which demonstrated 15 percent deviations heritability was estimated to be h2 =0.15.  Palpation score was not correlated with either body weight, egg weight or shell breaking strength.  There was an indication that precocious egg production was negatively correlated with palpation score. 

The review of literature showed a low prevalence of severe keel bone deformities in single or group-caged hens among three lines.  In contrast, studies in 2011 and 2012 showed a relatively high (25%) prevalence of keel deformation in hens housed in aviaries reflecting the designs of modules in perches at this time.

The authors concluded that keel deformation is multifactorial with a genetic predisposition but with the predominant causation relating to housing system. Experience with aviaries has shown that design of modules, location of perches and aisle-width influence keel damage.  Ameliorative approaches include management which encourages developing balance and pectoral musculature in pullets by housing in rearing modules compatible with the laying system. Additional approaches include adjusting light levels and confining pullets in modules for up to three weeks after 16-week transfer.  With the adoption of aviaries for commercial production of eggs as an alternative to conventional cages, directed studies are required  to understand the factors which contribute to keel deformities and also the effect on production and welfare.

*Icken, W. Genetic aspects of keel bone deformities and fractures determined by palpation in laying hens. Lohmann Tierzucht Newsletter. December 2017

 

(SMS067-18 January 9th 2018)