The four Cytologic stages of the Canine Oestrous cycle using vaginal cytology

Proestrus

This is usually seen as the first sign of the breeding cycle and it is known as the Dam “coming into season”. It usually lasts for around nine days on average but there is large variations between dogs. Usually you Dam will start to “flag” another dog and also male dogs start to show interest in your Dam but she is usually non receptive to their advances.

At this stage we see mixed cell types with red blood cells with Nucleus still predominant in the cells.

Estrus

This is the time when a female responds to the dogs advances and can last around 9 to 11 days and can also be detected by behavioural signs. ovulation occurs during this period and this indicates the optimum time for breeding. The Dam’s bleeding decreases and the vulva becomes soft and the Dam responds to stimulation by rubbing the back at the top of the tail.

At this stage it shows predominantly cornified epithelial cells with little or no Nucleus present in the cells.

Diestrus

The female becomes less interested in other dogs and behaviour starts to return to normal

At this stage we see the cells revert back to basal cells, with fewer red blood cells and Nucleus start to return in the cells.

Anestrus

At this stage of the cycle there should be no bleeding and your Dam’s vulva should have returned back to normal

At this stage we now just have basal cells.