Exploration of known stereotypic behaviour-related candidate genes in equine crib-biting.

The study investigated potential genetic links to a stereotypic behaviour in horses known as crib-biting but found them to be not significant, indicating that other studies on larger sample sizes are required.

Introduction and Objective

• This research primarily intended to determine the genetic susceptibility to the stereotypic oral behaviour known as crib-biting in horses. Crib-biting is an activity in which a horse grips an object with its incisor teeth and pulls back while making a characteristic grunt.
• Environmental factors such as stress, gastric discomfort, and frustration due to stall restrictions have been suggested as potential causes. However, this study aimed to test genetic associations, focusing on known or suspected genes related to stereotypic behaviours.

Methodology

• The researchers conducted a candidate gene study with a case-control design. The sample size included 98 horses exhibiting crib-biting (cases) and 135 control horses (not displaying the behaviour).
• Two horse breeds were used in the study: Finnhorses and half-breds. The control horses were all more than ten years old and had no prior history of crib-biting.
• A detailed survey was obtained from the owners to gather in-depth phenotypic information on the crib-biting behaviour exhibited by the horses.
• The researchers genotyped single nucleotide polymorphisms flanking the candidate genes, either through Sanger sequencing or Taqman assays.

Results

• The affected horses were reported to have started crib-biting at a young age and had shown this behaviour for more than a year. These horses typically crib-bite after eating or when stressed.
• However, when the researchers compared allele frequencies between the cases (crib-biting horses) and controls (non-crib-biting horses) for each breed, they found no significant evidence of an association at any of the tested loci.

Conclusion

• The results suggest that the previously studied stereotypic genes do not constitute major risk factors for crib-biting in horses.
• The study emphasises the need for further genome-wide studies, with larger sample cohorts, to get a more definitive understanding of genetic susceptibility to crib-biting in horses.