Answer: estrum

AnswerCrossword Clue
estrumthe period of heat in female mammals, also OESTRUM, ESTRUS, OESTRUS
estrumthe period of heat or rut; the period of maximum sexual receptivity of the female
estrumseries of physiological changes in sexual and other organs in female mammals, extending from one period of heat to the next, accompanied by behavioral changes indicating interest in mating