After the publication of this article, a number of concerns were raised in relation to different aspects of the research reported. The PLOS ONE editors carried out an evaluation of the history of the manuscript, which revealed that due to a failure in the peer review process, several aspects of the research were not adequately evaluated before publication.

As a result, the PLOS ONE editors have undertaken a thorough re-examination of this study, involving both external and internal advisers. This assessment has revealed the following concerns regarding the study:

1. The description of the alleles in the article is inadequate.
2. There are concerns over the study design employed to study the association; a single-gene association study based on Cox-2 or a genome-wide association study have been recommended as more appropriate approaches to study this association.
3. The validity of the control population employed in the study is compromised as it involved a different breed.
4. There are concerns about the strength of the evidence shown to support an association between the Cox-2 variant and the dogs' phenotypes, as the evidence from other breeds suggests that this may be a neutral DNA variant.

In the light of the concerns outlined above, the PLOS ONE editors are issuing this Expression of Concern in order to make readers aware of the concerns about the reliability of the results and conclusions reported in the article.