The oestrus period in sow is of the duration of

The oestrus period in sow is of the duration of 40 - 45 h.
Oestrus is the period in the sexual cycle of female mammals, except the higher primates, during which they are in heat i.e., ready to accept a male and to mate.
The oestrous cycle in pigs spans 18 - 24 days. It consists of a follicular phase of 5 - 7 days and a luteal phase of 13 - 15 days. During the follicular phase, small antral follicles develop into large, pre-ovulatory follicles.