Studies into mortality due to feather pecking have in the past pointed to genes as playing a substantial role in cannibalism.
Now, the Animal Breeding and Genomics of Wageningen University and Research and Hendrix Genetics have investigated the genomic regions associated with survival time in laying hens.
Survival is an important welfare and economic trait in laying hens and feather pecking behaviour is the main reason for reduced survival. Survival is a socially affected trait, because the survival time of a hen depends not only on her own ability to avoid being pecked but also on the pecking behaviour of her group mates.
Scientists know that direct and social genetic effects contribute about 50% of the total heritable variation in laying hens with intact beaks. But they did not know the genes responsible for the direct and social genetic effects.
As a result, they carried out a genome-wide association study using genotype and phenotype data on three crossbred White Leghorn layer lines provided by Hendrix. Hens had intact beaks and were kept with sibs in traditional 5-bird battery cages in Kitchener, Canada.
Single-nucleotide polymorphisms (SNPs) effects were estimated one by one, for both direct and indirect effects. The results showed several SNP’s associated with direct effects on survival time, but none with indirect effects. In one of the crosses, a clear direct SNP-effect was found on chromosome 2, close to the GAPA receptor gene (GABBR2).
In another cross, the same region was associated with the social effect, although not significant. The favourable allele had a positive effect on both the survival time of the individual and its group mates.
The GABA receptor gene plays an important role in the regulation of neurotransmitters in the brain. Several studies have shown that GABA plays a role in psychological and behavioural stress in many species and is associated with behavioural disorders.
The results have been published in Genetics Selection Evolution.