1) Prooestrus 
(from the article `dog`) The heat cycle of the female lasts from 18 to 21 days. The first stage is called proestrus. It begins with mild swelling of the vulva and a bloody ... ...produces a phenomenon known as the estrous cycle. Estrus, or `heat,` typically coincides with ovulation, and during this time the female is ... [2...
Phase of the estrous cycle preceding estrus during which the graafian follicle undergoes maturation. Applies to animals. ... (12 Dec 1998) ... 
(pro-es´trәs) the period of heightened follicular activity preceding estrus.
Type: Term Pronunciation: prō-es′trŭs Definitions: 1. The period in the estrus cycle preceding estrus, characterized by the growth of the graafian follicles and physiologic changes related to estrogen production. Synonyms: proestrum
In the estrus cycle, the period just before estrus.
The period immediately before estrus in most female mammals, characterized by development of the endometrium and ovarian follicles.
Proestrus is the beginning of the bitchThe part of the bitches season or cycle during which a bloody vaginal discharge is seen.
the period immediately preceding estrus.