Genome-Wide Association Analysis of Hippocampal Neuroplasticity as an Indicator of Stress Responsiveness in Laying Hens (Gallus gallus domesticus).

Environmental stressors in commercial poultry systems can negatively affect bird welfare, although individuals vary considerably in their responses. Neuroplasticity within the hippocampus, measured through the density of doublecortin-positive (DCX+) neurons, provides a potential biomarker of stress experience in laying hens. However, the genetic basis underlying variation in this biomarker remains poorly understood. A total of 42 H&N and Hy-Line Brown hens housed in a multitier free range and enriched cage system, respectively, were genotyped using Genotyping by Sequencing, yielding over 200 000 SNP markers after initial filtering. Hippocampal tissue sections were immunostained for DCX to quantify the density of highly plastic neurons. A genome-wide association analysis identified 19 genomic regions across eight chromosomes within the top 1% of windows explaining the greatest proportion of genetic variance in the neuroplasticity phenotype. Within ±100 kb of these regions, 39 annotated genes were identified, several of which are involved in cellular regulation and genetic information processing pathways. Notably, PIK3R6, VPS37D, STX1A, BAZ1B, HGH1, MAF1, MAPK15, and PIT54 emerged as positional candidate genes potentially contributing to variation in stress responsiveness. These findings provide preliminary insight into the genetic architecture of hippocampal neuroplasticity in laying hens and highlight candidate genes that may contribute to individual differences in stress response, with potential implications for breeding strategies aimed at improving poultry welfare.