Studies on Breeding Failures in Dogs: A Review

The domestic dog is a non-seasonal breeder. The female is monestrus and has a reproductive cycle that is marked by extended periods of proestrus and estrus. The estrous period is characterized by an estrogen peak that coincides with rising circulating progesterone concentration prior to ovulation. After estrus is diestrus and then anestrus, with the ovarian cycle regulated by the hypothalamic-pituitary-gonadal axis. In the male spermatogenesis is controlled by the hypothalamic-pituitary-gonadal axis with testosterone playing a vital role. The reproductive cycle of most wild canids is similar to that of domestic dogs. Diestrus is followed by an extended period of ovarian inactivity. The causes of breeding failure in dogs are numerous and require thorough investigations for accurate diagnosis. Breeding failures can be infectious or non-infectious. Among the infectious causes in the bitch, bacterial endometritis was found to be responsible for the majority of reported cases. Non-infectious causes include primary and secondary anoestrus, cystic conditions of the uterus, and degenerative diseases of the endometrium. In the male, the causes can also be infectious and non-infectious. Non-infectious causes like bilateral cryptorchidism and acquired anatomical abnormalities can also cause male infertility. Spermatocele or sperm granulomas, obstruction of the genital ducts or inguinal or scrotal hernia, and prostatitis lead to infertility. Infections can lead to orchitis/epididymitis, with alteration of the quality of the semen. Nutrition also has important implications for reproductive performance. Undernutrition can result in loss of body condition, delay the onset of puberty, and ultimately lead to infertility.