The bitch’s oestrous cycle: stages, variation and checks

The four stages of the cycle vary in length, and external signs do not identify the fertile period precisely. Reproductive management requires veterinary assessment.

The stages do not follow an identical timetable

Pro-oestrus, oestrus, dioestrus and anoestrus describe behavioural, anatomical and hormonal changes. The observed duration of each stage can vary between individuals.

Discharge or willingness to mate, on their own, cannot establish when ovulation occurs or diagnose pregnancy.

Management requires professional assessment

Variation in the cycle and the limitations of external signs make veterinary assessment appropriate when breeding is planned or when the observed pattern raises concerns.

Drug-induced suppression of the cycle and management of an unwanted mating are not do-it-yourself procedures.

Sources and documentary update

Documentation updated on 24 July 2026. This article summarises the official sources or professional guidance listed on the page and does not replace diagnosis, prescribing or instructions from a veterinarian. For any medicine, the summary of product characteristics or package leaflet for the specific presentation remains authoritative.

• Merck Veterinary Manual — Canine reproductive cycle (accessed 24 July 2026)

Editorial transparency: sources are listed so that the documentation can be checked. Professional review is stated only after genuine approval by a qualified, identifiable person.