Comparison of fertility data from vaginal vs intrauterine insemination of frozen-thawed dog semen: A retrospective study

Fertility data from 327 artificial inseminations (AIs) using frozen-thawed dog semen are presented here. The AIs were performed in 274 bitches using s emen from 185 males of 76 breeds. The data cover all AIs conducted during 1 983 through 1995 at Cryogenetic Laboratories (CLONE) in the United States w ith AKC-registered and research bitches, and all AIs carried out at the Dep artment-of Obstetrics and Gynecology at the Swedish University of Agricultu ral Sciences in Uppsala, Sweden, using semen frozen by CLONE, in 0.5-mL str aws. Semen was frozen using a standardized, three-step liquid nitrogen vapo r freezing method. Whelping rates >70% were obtained when post-thaw motilit y was 40% or higher. The inseminations were made either directly into the u terus using:transcervical catheterization with the Norwegian catheter (NIU; 167 Als) or a fiberoptic endoscope (EIU; 19 AIs), or in the cranial vagina (VAG; 141 AIs). Resulting whelping rates were 84.4% (NIU), 58.9% (VAG; P<0 .001), and 57.9% (EIU). Increasing the number of VAG AIs per cycle from 1 t o 2 enhanced the whelping rate (P<0.05). The mean interval from the first A I to whelping was 61.8 +/- 2.4 d, and was longer for VAG AIs (62.7 +/- 2.7 d) than for NIU AIs (61.2 +/- 2.1 d; P<0.001). The mean interval from the l ast AI was 60.1 +/- 1.9 d, and aid not differ between VAG AIs (60.2 +/- 2.2 d) and WW AIs (60.0 +/- 1.6 d). Gestation length was not influenced by bre ed or litter size. a total of 1158 pups resulted from the 327 AIs. Litter s ize was 5.4 +/- 3.0 (NIU), 3.0 +/- 2.7 (VAG; P<0.001), and 6.0 +/- 2.1 (EIU ). Litter size was also influenced by breed (P=0.006) and, for VAG Als, by the number of inseminations performed per cycle (P=0.009). This study is th e largest that has been carried out on frozen-thawed dog semen AI. It shows that using a good method for cryopreservation, together with nonsurgical i ntrauterine AI employing the Norwegian catheter, can yield whelping rates a nd litter sizes similar to those reported from well-controlled natural mati ngs. Furthermore, this is the first study to show that intrauterine deposit ion of frozen-thawed dog semen results in a significantly higher whelping r ate and larger litter size than vaginal deposition. (C) 1999 by Elsevier Sc ience Inc.