ObjectiveThe overall objective of this project is to investigate the transfer of behavioural traits and stress susceptibility from laying hens to their offspring through changes in egg composition and epigenetic mechanisms. We also aim to determine whether egg traits and offspring behaviour differ with age of breeder flock and whether some genotypes are more sensitive to these effects than others.
BackgroundGenotype, environmental effects and early-life history of a hen determines her behavioural response. Additionally, behaviour can be altered through epigenetic mechanisms. In birds, maternal hormone profiles alter the concentrations of steroid hormones in the yolk, which are likely mediators of epigenetic effects. Environmental challenges or stressors experienced by a mother can affect the general development of her offspring (e.g. impair growth and stress-axis activity and affect fearfulness, cognitive abilities and social behaviour). The effects may be transient, or they may affect the germ-line resulting in alterations in gene expression that are passed down to subsequent generations. The consequences of epigenetic alterations in behaviour phenotype are highly relevant in a production environment. The effects of various types of maternal stress on egg and offspring characteristics as well as on gene expression have been demonstrated in domesticated birds. The degree to which a hen transfers epigenetic information to her offspring may depend in her genotype. In addition to changes in the epigenome, there are other potential mechanisms for maternal effects on behaviour in birds. These findings suggest that: 1) the experience of a parent flock of layers could affect the behaviour of the laying hens that they produce, 2) that the potential to pass down these effects may vary with genotype and 3) that age of parent flock may impact some aspects of behavioural development in their chicks. Canadian producers are replacing conventional cages with furnished cages and cage-free systems for laying hens. Failure to adapt well to these systems can result in reduced flock uniformity, higher mortality and more floor eggs. Therefore finding ways to reduce fear in hens and to facilitate their learning and adaptation to different housing environments is of significant importance. Little previous research has investigated the effect of either rearing experience, housing system or flock age on offspring behaviour or stress reactivity in more practical settings. Few studies exist that have compared the susceptibility of traditional or more highly select commercial hybrid strains of birds to various developmental or epigenetic effects. Matching the behavioural phenotypes of laying hens with different housing environments that they are to be housed in is of significant importance to the Canadian layer industry. Our results can be used for identifying best practices for rearing and housing of both breeder and layer flocks.
Funding$679,120 (AAFC/CPRC $477,386*, LH Gray & Sons $69,000, Poultry Industry Council $47,800, Egg Farmers of Canada $60,000, Lohman Tierzucht Canada $24,934 (in-kind))
*This research was part of the Poultry Science Cluster 2 which was supported by AAFC as part of Growing Forward 2, a federal-provincial-territorial initiative.