Proestrus Bleeding – Species

Proestrus bleeding occurs in:

Correct Answer: Bitch

Proestrus bleeding (serosanguineous vulvar discharge) is a characteristic feature of the bitch. It occurs during proestrus (the phase before true estrus/heat) due to estrogenic stimulation of the uterine endometrium causing diapedesis of red blood cells.

Key Points

• Proestrus in the bitch lasts approximately 9 days, during which the bloody discharge is present.
• The bitch is NOT in true standing heat during proestrus — she may attract males but will NOT stand for mating.
• True standing heat (estrus) begins when the discharge becomes lighter/straw-colored and she accepts mounting.

Comparison: Types of Bleeding in Domestic Animals

• Proestrus bleeding: Bitch ✔ (before estrus)
• Metestrus bleeding (post-estrus): Cattle — occurs 1–2 days after end of estrus due to withdrawal of estrogen causing uterine capillary rupture.