Fertility in dogs in relation to semen quality and the time and site of insemination with fresh and frozen semen.

In this study 470 bitches were inseminated; 405 with fresh semen into the cranial vagina and 65 with frozen semen transcervically into the uterus. The pregnancy rate was 65.7% with fresh semen and 41.5% with frozen. When corrected for stage of oestrus at the time of insemination and for semen quality the pregnancy rate was 83.8% with fresh semen and 69.3% with frozen semen. The pregnancy rate improved with an increase in the number of inseminations. Inseminations with fresh semen before the time of ovulation (less than 17.3 nmol progesterone/l) were often successful. With frozen semen the peripheral plasma level of progesterone at the time of insemination was greater than 30 nmol/l in all but 1 of the bitches that became pregnant. This difference is assumed to be attributable to a longer survival time of several days for fresh semen than for frozen-thawed semen. Cytological scoring was a satisfactory method for determining the stage of oestrus when using fresh semen, but more precise methods are needed when using frozen semen. Semen quality was difficult to correlate with fertility. Pregnancies were obtained with fresh semen of inferior quality, although the litter size was smaller. With frozen semen no pregnancies resulted when the semen quality was poor. Litter size was estimated to be 21.5% smaller in bitches inseminated with fresh semen compared with naturally mated bitches. Litter size in bitches inseminated with frozen semen was 23.3% smaller than in bitches inseminated with fresh semen. Puppy deaths occurred in 35.5% of the litters in this study. The overall puppy death rate during the first 3 weeks of life was 11.9%. Although not statistically significant, there was a tendency for bitches treated with antibiotics at the time of mating or during early pregnancy to have a higher pregnancy rate and a larger litter size. There was also a tendency for breed differences in pregnancy rate, although not significant.