1. chimera: After dog mating, a series of physiological changes will occur in vagina, including chimera. Chimera refers to vaginal bleeding that may occur within 8 ~ 15 days after mating. This is a normal physiological reaction, so don't worry too much.
2. Vaginal infection: Sometimes, dogs may be infected by bacteria during reproduction, leading to vaginal inflammation. This may lead to bleeding. It is recommended to take the dog to the vet for examination and treatment.
3. Uterine prolapse: Uterine prolapse is a serious complication, which may occur within a few days or weeks after mating. In this case, the dog may have a lot of vaginal bleeding. This is an emergency, you should see a doctor at once.
4. Ectopic pregnancy: In some rare cases, dogs may have ectopic pregnancy, that is, the position of embryo implantation is incorrect. This may lead to uterine blood vessel rupture and vaginal bleeding. This also requires urgent treatment by veterinarians.