Light in early life: understanding the mechanisms of embryonic photoreception to improve poultry welfare and production

This project will use state of the art technology to investigate the mechanism by which light exposure during artificial incubation of bird eggs exerts positive effects on embryonic development, hatchability and post-hatch outcomes.

Poultry production is a major component of the agricultural sector in the UK and worldwide. Over 90 million eggs are set for incubation each month in the UK alone. Environmental conditions during incubation are vital for proper development and can have long lasting consequences post-hatch.

Hatchability and hatch synchrony are two areas of major industry concern, as low hatchability and asynchronous hatch result in chick loss. Reduction of hatch asynchrony and improvement of hatchability represents a key means to improve animal welfare and efficiency.

In commercial settings eggs are incubated in darkness but light exposure during incubation has emerged as a potential means of improving hatchability and hatch synchrony. Our understanding of how light exposure acts during incubation, and how it can be optimized remains limited. Our recent work has shown that extra-retinal photoreceptors (non-visual opsins) represent a widespread and evolutionarily ancient form of light detection and response that could readily mediate these developmental effects.

Our data has shown that extra-retinal photoreceptor expression begins at least several days before that of visual opsin expression and displays marked changes across the developmental time course. The project has 3 specific objectives:

1. Determine the anatomical localization and ontogeny of extra-retinal photoreceptors across development to establish the optimal wavelengths and timing of light delivery during incubation.

2. By using transcriptomic analysis, identify the neural and developmental pathways activated by light exposure during incubation focusing on identification of pathways related to hatch synchronicity. Specifically we will identify genes that show changes in expression in response to incubation under light versus dark conditions.

3. Elucidate if light detection by the extra retinal photoreceptors (VA opsin and melanopsin) mediate the positive effects of light exposure during incubation using gene edited opsin knockout chicken lines. Identify linkages between opsin mediated light detection and the endocrine system e.g. thyroid, melatonin and glucocorticoid systems as well as hatchability and synchrony of hatch.

These studies will provide unique insights into the mechanisms by which embryos are able to detect and respond to light cues. This understanding will inform not only commercial egg incubation, but inform a more detailed appreciation of how nocturnal light exposure may impact wild bird populations.

This timely project is relevant to the BBSRC strategic priorities: Welfare of Managed Animals, Animal Health, Sustainably Enhancing Agricultural Production, Healthy Ageing Across the Life Course and Technology Development for the Biosciences and the Roslin Institute's BBSRC funded Institute Strategic Program: Improving Animal Production and Welfare.

This project brings together a strong multidisciplinary team with exceptional skills in avian physiology as well as novel avian gene targeting and germ line transmission of mutated germ cells to generate a gene-edited line that can be used as a sterile host (due to absence of primordial germ cells) for transferred gene edited primordial germ cells. This technology will lead to highly efficient production of birds carrying the desired opsin mutation.