There are generally three reasons for dogs to have empty litters:

1. Improper breeding time: The ovulation time of a female dog is difficult to determine. If the female dog is bred too early or too late, the sperm may not be able to combine with the egg, resulting in Empty nest. In order to increase the chance of conception, the female dog can be bred multiple times before her estrus behavior stops.

2. Problems with male dogs: The semen of male dogs has low vitality or quality problems and cannot combine with eggs. Will lead to empty nests.

3. Reproductive system diseases of female dogs: Female dogs suffering from reproductive system diseases or infection with Brucella may cause miscarriage or inability to conceive.