A genetic study indicates that genes previously linked to stereotypic behaviors are not a major risk factor for crib-biting.
Crib-biting, or cribbing, is a stereotypic behaviour in which the horse grasps a fixed object with its incisor teeth, and draws air into the cranial oesophagus, before expelling it with a characteristic grunt.
Various factors have been suggested as a cause for the behaviour, including gastric discomfort and lack of sufficient environmental stimulation.
Stereotypies are generally considered to be more a response to an imperfect environment than simply bad behaviour on the part of the horse.
But is there a genetic component?
The latest issue of Equine Science Update reports that scientists at the University of Helsinki, in Finland, compared crib-biting and non-crib-biting horses, looking specifically at genes known or suspected to be related to stereotypic behaviors.
In particular, they looked at genes such as Ghrelin, Ghrelin receptor, Leptin, Dopamine receptor, μ-opioid receptor, N-cadherin, Serotonin receptor and Semaphorin.
Two groups of horses were compared.
Horses in the crib-biting group had started to display the behaviour at any early age, and had done so for at least a year. They tended to crib-bite after feeding or when stressed.
The non-crib-biting control group of horses were all over 10 years old and had never been seen to crib-bite.
The researchers analysed the candidate genes in both groups and compared the allele frequencies between the cases and controls for each breed separately.
They could find no evidence of an association at any of the tested loci.
“These results suggest that the previously known stereotypic genes are not major risk factors for crib-biting in horses,” the researchers concluded.
They suggested that further whole genome studies involving larger groups of crib-biting and non-crib-biting horses were required.
Hemmann K, Ahonen S, Raekallio M, Vainio O, Lohi H.
Exploration of known stereotypic behaviour-related candidate genes in equine crib-biting.
Animal. 2014 Jan 6:1-7. [Epub ahead of print]