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 > or = 50% and percentage abnormal sperm < or = 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 < or = 6 years old 2 and 3 days after ovulation with semen of good quality from males < or = 8 years old.

Artificial insemination with frozen semen in dogs: a retrospective study.

In a retrospective study, from 1994 to 1998, of inseminations with frozen semen in dogs, a total of 312 bitches of 70 different breeds were inseminated with imported (n = 183) or domestic (n = 129) semen. The overall whelping rate was 70% and mean (+/- SEM) litter size was 5.3 +/- 0.2 pups. The whelping rate was higher after intrauterine insemination (71%; n = 305) than after intravaginal insemination (29%; n = 7; P < 0.05). Timing of insemination was crucial; timing classified as optimal resulted in a higher whelping rate and larger litter size (P < 0.05) than did timing classified as early, late or too late. In the too late category, none of the bitches (n = 5) whelped. For optimal timing, whelping rate and mean (+/- SEM) litter size were 76% (n = 252) and 5.6 +/- 0.2, for early 33% (n = 6) and 1.5 +/- 0.5, and for late 47% (n = 19) and 2.8 +/- 0.7. Two inseminations yielded a higher whelping rate (P < 0.05) and greater mean litter size (P < 0.05) than that of one insemination, 77% and 5.6 +/- 0.3, and 60% and 4.6 +/- 0.3, respectively. However, the results obtained after one insemination were poorer partly because of an over-representation of late insemination in this group. Semen classified as of poor quality (progressive motility < 50% or percentage of abnormal spermatozoa > 20%) gave a lower whelping rate (53%) than did semen of medium (progressive motility = 50%) or good quality (progressive motility > 50% and percentage of abnormal spermatozoa < 20%), which gave whelping rates of 76 and 74%, respectively (P < 0.05). The mean litter sizes were not significantly different. Eighty-two per cent of bitches (120 of 147) inseminated twice into the uterus at a time classified as optimal with frozen semen of good or medium quality whelped. The mean (+/- SEM) litter size was 5.6 +/- 0.3 pups in this group. These results show the potential of transcervical intrauterine insemination for routine artificial insemination in dogs.

The optimum time for single artificial insemination of blue fox vixens (Alopex lagopus) with frozen-thawed semen from silver foxes (Vulpes vulpes).

During the breeding season of 1991 a total of 608 blue fox vixens aged 1 to 6 years (2.3 +/- 0.1 years, mean +/- SEM) from 2 farms were artificially inseminated intrauterine once with frozen-thawed silver fox semen (1 ml dose containing a total of 150 million spermatozoa). The vixens were allocated to 3 different groups according to the time of insemination. Vixens in Group 1 (n = 203), Group 2 (n = 198), and Group 3 (n = 207) were inseminated on the first, second or third day after the peak value of vaginal electrical resistance, respectively. An overall conception rate of 75% (456 of 608) and 6.0 +/- 0.1 (mean +/- SEM) cubs per litter was obtained. Conception rates and mean litter sizes were significantly different between groups of vixens with respect to day of insemination (P = 0.02, Chisquare, Kruskall-Wallis Test). Vixens inseminated on the second day (Group 2) had the highest conception rate (81%) and the largest mean litter size (7.0 +/- 0.2 cubs) of the three groups, while those inseminated on the third day (Group 3) had the lowest conception rate and mean litter size (70%, 5.4 +/- 0.3 cubs).

The effect of sperm number on fertility in blue fox vixens (Alopex lagopus ) artificially inseminated with frozen silver fox (Vulpes vulpes ) semen.

During the breeding seasons of 1989 and 1990, a total of 617 blue fox vixens aged 1 to 6 years (mean +/- SEM, 2.6 +/- 0.1) were inseminated with frozen silver fox semen with either 150 million (n = 213, 1989 + 1990), 100 million (n=172, 1990), 75 million (n = 119, 1989) or 37.5 million (n = 113, 1989) spermatozoa per insemination. Two intrauterine inseminations, each with an insemination volume of 1.0 ml, were performed at 24-hour intervals on the first and second days after maximum vaginal electrical resistance was measured. Conception rates were 87% (186 of 213) with 150 million spermatozoa per insemination, 85% (146 of 172) with 100 million, 77% (91 of 119) with 75 million and 68% (77 of 113) with 37.5 million. The mean numbers of cubs per litter +/- SEM for the four groups were 7.6 +/- 0.2 (168 registered litters), 7.5 +/- 0.3 (115 litters), 6.4 +/- 0.4 (86 litters) and 6.4 +/- 0.4 (75 litters). A negative effect on both the conception rate and mean litter size at whelping was observed with decreasing sperm numbers (conception rate percentage: p = 0.0001, Chi-square, litter size: p = 0.02, Kruskal-Wallis Test). Only the two larger numbers of spermatozoa gave litter sizes comparable to those obtained by artificial insemination (AI) with fresh semen.

Effect of melatonin implants on reproduction in the male silver fox (Vulpes vulpes).

In June 1987, when the testes were fully regressed, 5 males were given s.c. implants of 40 mg melatonin. The same treatment was repeated in August and October 1987. Five males served as controls. Plasma concentrations of melatonin increased significantly in treated males and were still elevated at the end of the study in April 1988. The changes in testicular volume and blood plasma concentrations of testosterone in response to GnRH indicated that melatonin administration promoted testicular development. However, testicular regression was observed earlier in treated than control animals, perhaps because of refractoriness to melatonin or to a down-regulation of melatonin receptors. Semen was collected and frozen in November 1987, 2 months ahead of the natural breeding season, from the melatonin-treated males, and 10 blue fox vixens were inseminated the following breeding season: 9 vixens conceived, and the average litter size was 7.6 +/- 0.5. The results demonstrate that melatonin treatment initiated during exposure to naturally long days (a) promotes testicular development in a way similar to an artificial short photoperiod and (b) may induce a refractory condition after an extended period of treatment.

Photoperiodic regulation of reproduction in the male silver fox (Vulpes vulpes).

Six silver fox males were exposed to short days (6L:18D) from February, when the testes were fully developed, until June 1986 (Group 6L). Eight males maintained in natural daylight served as controls (Group N). Histological sections from the testes of 2 males in Group 6L killed in June indicated full spermatogenic activity. Three blue fox vixens inseminated the following year with semen collected and frozen in June from 3 males in Group 6L failed to produce litters. One possible explanation for the reproductive failures could have been that the high environmental temperatures in June influenced semen quality. There was no significant difference (P greater than 0.05) in LH release in response to GnRH stimulation in June, but testosterone response to LH release was significantly higher (P less than 0.01) in animals subjected to a restricted photoperiod, demonstrating that testicular testosterone production was maintained longer than in control animals. Two males in Group 6L were retained in 6L:18D from June until December 1986 and then exposed to natural daylight until the end of the study in May 1987 (Group 6L:6L:N). These males started to shed their winter coat and showed clinical signs of testicular regression in December, i.e. after approximately 11 months exposure to 6L:18D. The 2 remaining males in Group 6L were moved to cages with natural daylight in June 1986, where they were kept until the end of the experiment (Group 6L: N:N). These males displayed testicular regression soon after the change in photoperiod but maintained their capacity for testicular redevelopment during the following breeding season.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrical resistance of vaginal secretion in the bitch.

Five multiparous and four nulliparous bitches had the electrical resistance of vaginal secretions measured by an ohmmeter. The bitches were examined daily, starting on the first day of vulval bleeding and continuing until the first day when exfoliated vaginal epithelial cells became predominantly noncornified. In contrast to cattle, sheep, and swine, the electrical resistance of the vaginal secretions in the bitch increases during pro-oestrus and continues to be high while the bitch is showing oestrous behaviour and a high percentage of eosinophilic superficial cells in the vaginal smear. Ovulation, as determined by a rise of serum progesterone above 5 ng/ml, occurs within the period of elevated resistance. Optimal conditions for conceptions coincide with the last 3 d of elevated resistance.