Artificial insemination with frozen semen in dogs: A retrospective study of 10 years using a non-surgical approach

From 1994 to 2003, a total of 526 bitches of 99 different breeds were artificially inseminated in 685 estrus cycles with domestic (n=353) or imported (n=332) frozen-thawed semen from 368 males. The overall whelping rate was 73.1% and mean (±S.E.M.) litter size 5.7±0.1 pups. The whelping rate was higher after intrauterine insemination (75.0%; n=665) than after intravaginal insemination (10.0%, n=20; P<0.05). Insemination at the optimal time resulted in a higher whelping rate (78%, n=559; P<0.01) and larger litter size (5.8±0.2; P<0.05) than inseminations performed late or too late (55.7% and 4.5±0.5, n=61). Two inseminations (n=384) yielded a higher whelping rate (P<0.05) and mean litter size (P<0.01) than one insemination (n=241), 78.1% and 6.0±0.2 and 70.5% and 5.1±0.2, respectively. For inseminations performed at the optimal time, however, the whelping rate was not significantly different for bitches inseminated twice (79.3%, n=358) versus once (76.8%, n=168), but the litter size was larger (6.0±0.2 and 5.3±0.3). Semen classified as of poor quality (progressive motility <50% or percentage abnormal sperm >20%) resulted in a lower whelping rate (P<0.01) than semen classified as of good quality (progressive motility ≥50% and percentage abnormal sperm ≤20%), 61 and 77%, respectively. Small breeds (n=50) had a smaller litter size (3.9±0.3; P<0.01) than larger breeds (medium [5.7±0.3, n=94], large [5.9±0.2, n=295] or giant breeds [6.1±0.5, n=62] [P<0.01]). Bitches older than 6 years had a lower whelping rate (68.2%) than younger ones (77.0%; P<0.05). The duration of pregnancy was longer (P<0.01) for bitches with a litter size of <3 pups (61.7±0. 4 days, n=30) than for bitches with larger litters (60.5±0.1 days, n=177). These results show the potential of transcervical intrauterine insemination for routine artificial insemination in dogs. The results with frozen semen inseminations were optimised by inseminating bitches ≤6 years old 2 and 3 days after ovulation with semen of good quality from males ≤8 years old.