The artificial insemination has become a well- established method in the breeding of bitches, and evaluation of the factors that may potentially affect pregnancy success is essential. For this reason, it is essential to evaluate the factors that may affect fertility of the bitch when artificial insemination is performed. Serum progesterone concentrations and vaginal cytology have been used to determine the time of ovulation and stage of the estrus cycle. This study aimed to evaluate the artificial insemination method, the serum progesterone concentration, the breed size, age, the whelping number, vaginal cytology parameters, and their interactions on pregnancy success in bitches. A total of 607 bitches that had undergone reproductive consultation with the Mexican Canine Federation from January to December 2016 were enrolled in the present study and assigned to one of 2 artificial insemination methods (intravaginal and transcervical) using fresh semen. Determination of the estrus cycle phase and the time of Artificial insemination was based on vaginal cytology and serum progesterone concentrations. Bitches inseminated by the transcervical technique had a higher pregnancy rate with respect to females inseminated by the intravaginal technique (P < 0.05).

 

Moreover, females with a serum progesterone concentration of 5-10 ng/mL had a greater probability (> 4 times) of getting pregnant than animals with lower or higher progesterone concentrations (P < 0.05). Bitches inseminated by the intravaginal technique and with serum progesterone concentrations >10 ng/mL had a considerable reduction in pregnancy (P < 0.05) compared with females with < 10 ng/mL serum progesterone or with bitches inseminated by the transcervical technique. In conclusion, serum progesterone concentration, the artificial insemination method, and superficial cells without a nucleus, modified the pregnancy rate in bitches.