The Interaction Between Photoperiod and Nutrition and Its Effects on Seasonal Rhythms of Reproduction in the Ewe1

Abstract

In sheep, the seasonal patterns of reproductive activity are driven primarily by the annual photoperiodic cycle, but can also respond to other environmental factors, such as nutrition, yet little is known about the mechanisms underlying this interaction. This study was designed to define the interaction between photoperiodic and nutritional cues on seasonal patterns of ovarian activity, and to determine if there is a central interaction between these cues. Groups of Ile-de-France ewes were maintained in two nutritional states (restricted and well fed) under a simulated annual photoperiod of 8-16 h of light per day over two breeding seasons. At the end of the first breeding season, half of the animals of each group were ovariectomized (OVX) and fitted subcutaneously with estradiol implants. Low nutritional status shortened the season of ovarian activity, determined from the pattern of progesterone concentrations, by modifying the timing of seasonal transitions between periods of ovarian activity and anestrus. The same results were observed for the seasonal rhythm of neuroendocrine activity, assessed in the OVX ewes, from the pattern of luteinizing hormone concentrations. These results were then confirmed for neuroendocrine activity induced by a photoperiodic treatment. We conclude that nutrition centrally modulates the interpretation of photoperiod to affect seasonal reproductive transitions. The mechanisms of this interaction are discussed in the paper.

Thyroid Hormone and Seasonal Rhythmicity

“…Such a process bears critical adaptive value, best exemplified in species that hibernate (e.g., groundhog) or undergo daily torpor (e.g., Siberian hamster), which have evolved a strategy to build up abdominal fat depots during spring/summer to survive the harsh winter season (1, 61). Photoperiodic cues and the metabolic status interact in many seasonal breeders, including sheep (66, 67), goats (68, 69), and horses (70). In all these species, feeding modulates the duration of the breeding season and/or depth of the anestrus.…”

Annual rhythms that underlie phenology: biological time-keeping meets environmental change

“…These include food [53,54], social interactions [55], weather conditions [8] and especially ambient temperature [56]. In hibernating mammals, changes in temperature can advance phases within circannual rhythms.…”

The comparison of reproductive hormone receptor expressions of the sheep ovary and hormone concentrations in two Chinese breeds

“…Additional environmental factors such as photoperiod, nutrition and temperature also participate in the regulation of seasonal reproductive activity (Estrada-Cortés et al, 2009;Forcada & Abecia, 2006;Rosa & Bryant, 2003). Among these, photoperiod is regarded as the most important factor in the seasonal regulation of reproduction (Menassol, Collet, Chesneau, Malpaux, & Scaramuzzi, 2012;Nishiwaki-Ohkawa & Yoshimura, 2016). Numerous studies have confirmed that seasonal photoperiodic information is conveyed to the pineal gland through the retina.…”