This is the time at which female dogs will have their first estrous cycle.

The estrous cycle in the female is 28 days with a three-day period of estrus.

However, hormones of the estrous cycle seem to be involved.

In an estrous cycle, the lining degenerates back to normal size.

Domestication can affect estrous cycles due to changes in the environment.

The female estrous cycle is shorter, but happens in this time.

P4 is highest in the diestrus phase of the estrous cycle.

The estrous cycle lasts about 46 days and the female usually is in heat for 6-7 days.

The estrous cycle lasts about 19-22 days, with the average being 21 days.