Virtually all animals undergo marked changes in body structure, function and behavior which enable them to adapt to, and survive, the hardships of a seasonally changing natural environment. The overall goal of the program is to understand the regulation of seasonal reproduction in an animal of world-wide importance, the domestic sheep. It has become clear through recent research that the process of seasonal reproduction in sheep is generated spontaneously by a self-sustained endogenous rhythm of neuroendocrine activity. Changes in day length provide time cues which permit appropriate phasing of this endogenous rhythm with cyclic changes in the environment. The specific goal of the research program is to define those portions of the annual cycle of day length which provide the temporal information leading to an appropriately timed breeding season, and to clarify the mechanisms by which this information is conveyed. The outcome of the research should lead to new insights into a fundamental problem of enormous biological significance and practical importance: the regulation of fertility. The results will also be more broadly applicable to a wide variety of physiological, metabolic and behavioral rhythms which form an integral part of the adaptive mechanisms in many animals. An understanding of these processes should have profound implications to the production of food and human nutrition as well as the reproductive biology of wild or endangered species that are seasonal breeders.
