one less laborious technique and more needs, the determination of the moment of the ovulao could better be studied. It can be affirmed that, generally, the ovulao occurs at the beginning of tero final of estro (or rutting). This means that, in a female whose estro lasted 3 days, the ovulao probably occurred enters the end of 2 and start of 3 day. The studies most recent demonstrate that the ovulao can after happen between 10 and 96 hours the beginning of estro, being that the great majority, occurs between 36 and 48 hours (Figure 9). Leitoas, on average, after ovulam 30 hours of the beginning of the rutting, whereas the nuts, between 40 and 50 hours. Some authors tell cases where the ovulao after occurred the end of estro. In relation to the duration of estro, diverse studies had been carried through with the objective to find factors associates to the ovulao and that they could be used to foresee the moment of the ovulao in the day the day of the farms. Of all the studied factors, the duration of estro showed to be more important. However, retrospect is about a measure, that is, the end of estro only can be determined after, when the ovulao already would have occurred.