Amir Fallahshahroudi research group

Genetic and Neuroendocrine Regulation of Avian Reproduction

Expressing appropriate responses to the upcoming seasonal changes in the environment is crucial for survival and fitness. Therefore, animals and plants of temperate zones use different environmental cues to anticipate and prepare themselves for the upcoming seasonal changes in resource availability, climate, and risk of infection. Temperate animals typically use day-length (photoperiod) as the most reliable anticipatory cue to predict the change of seasons. This ability to anticipate and react to photoperiod is referred to as photoperiodism. In animals, photoperiodism includes changes in reproduction, morphology, stress response, metabolism, immune system, and a diverse range of behaviors, such as migration and aggression.

Many domesticated animals, such as horses, goats, sheep, chickens, turkeys, and ducks, are photoperiodic and time their reproduction and other life histories based on the photoperiod. With more than 60 billion raised yearly, the domestic chicken is the most numerous and agriculturally important bird species on the planet. Similar to most other temperate birds and small mammals, chickens are long-day breeders, starting reproduction when the photoperiod gets longer than a certain threshold. Accordingly, the egg industry exploits this biological feature to synchronously trigger reproduction in laying hens. Therefore, commercial laying hens are raised in short days (~ 8 hours light per day) until they become 16-18 weeks old; then the photoperiod is suddenly increased to 13 – 14 hours per day to stimulate egg laying. This abrupt increase in the photoperiod to initiate egg laying is referred to as photo-stimulation. Importantly, very little is known about the underlying regulation, responses, and health and welfare implications of this commonly used management practice in laying hens.

Research on the model systems of photoperiodism, such as hamsters, quails, and songbirds, has shown that photoperiodism is much more than the activation of reproduction. Importantly, photo-stimulation triggers the transition from non-reproductive to reproductive life-history stages. Consequently, this major life-history transition shifts allocations of resources away from survival-enhancing mechanisms, such as immunity, to reproduction. In turn, this affects a wide range of physiological, behavioral, and immunological traits. However, despite probable health and welfare implications, these effects have not been comprehensively evaluated in the chicken. Additionally, the molecular and cellular regulation of photo-stimulation is not well-known in chickens.

My project aims to provide a multidimensional overview of photoperiodism in the chicken and assess its implications on the health and welfare of laying hens. To reach these goals, we plan to systematically characterize the effects of photo-stimulation on (i) physiology and behavior, (ii) immune cell profiles and immunocompetence, and (iii) cell-type specific gene expression in the hypothalamus.

Last modified: 2023-03-27