ESHS/HSS Annual Meeting

“A dose of rhythm:” light, melatonin, and the molecularization of environmental influences in out-of-season breeding of livestock (1930s-1990s)

• In Event: Invisible Actors in Biomedical and Environmental Sciences (I) & (II)

English Abstract

Controlling the timing and periodicity of reproduction was integral to transformations in livestock farming during the 20th century. Out-of-season breeding reduced unproductive periods in dairy and meat sectors and tuned animals’ sexual cycles with markets. This talk examines how attempts to induce out-of-season reproductive cycles in small ruminants acted as a crossroads for engagement with the environment in animal husbandry and the life sciences more broadly. Focusing on annual daylength cycles, it traces the evolving means by which agronomists and biologists explained and harnessed sheep and goats’ photoperiodic responses to intensify productions. I specifically analyze the molecularization of environmental influences, which introduced a discord in animals’ perception of seasons, between what eyes perceive and how the body responds.
I first outline the international research network that extended photoperiodism to small ruminants from the 1940s, progressively unravelling it at the molecular level. I then consider how sheep reproductive physiology became a nexus for animal husbandry, neuroendocrinology and chronobiology. From the 1980s, sheep sat at the intersection of experimental farm and laboratory, becoming not only an object of agricultural intensification but also a model for investigating pineal melatonin’s role in conveying photoperiodic information to the reproductive axis. Methods for controlling seasonality expanded from light treatments to melatonin implants. By mimicking the short-days signal directly inside the body, these implants bypassed the visual and aimed to trigger sexual activity independently of external photoperiods. I conclude by discussing biological and social limits to these methods for deceiving animals about their light environment.

Author

• Lucie Gerber, CNRS, SAGE, France