polyestrous

Polyestrous refers to a reproductive pattern in which females undergo multiple estrous cycles throughout the year. In polyestrous species, there is no single breeding season limiting fertility; rather, cycles can occur repeatedly during favorable conditions, though the frequency and duration of cycles can vary by species and environment. This pattern contrasts with monoestrous species, which have only one cycle per breeding period, and with seasonal breeders, whose cycles are restricted to particular times of the year.

The estrous cycle in polyestrous animals is driven by the hypothalamic-pituitary-gonadal axis. Hormones such as GnRH, FSH, LH, estrogen, and progesterone regulate the phases of the cycle—proestrus, estrus, metestrus, and diestrus—and ovulation may occur spontaneously in many species. If conception does not occur, the corpus luteum regresses and a new cycle begins after a luteal phase. Cycle length and the interval between cycles vary widely among species; for example, small rodents may cycle every few days, while cattle and pigs typically have cycles on the order of about three weeks.

Common examples of polyestrous species include many livestock and laboratory animals, such as cattle, pigs, and mice, as well as other mammals that exhibit frequent, year-round cycles. This reproductive strategy can enhance opportunities for pregnancy when resources and conditions are favorable, making it a key consideration in veterinary management, animal husbandry, and reproductive biology.