Reclamation of Canada’s threatened wood bison (Bison bison athabascae) herd is complicated by endemic disease. As part of an overall goal to conserve bison genetics, the specific objective of this study was to develop a protocol to control follicular wave emergence in bison for the purposes of ovarian superstimulation and collection of disease-free oocytes. In an initial study, the synchronizing effect of follicular ablation and estradiol (E2) treatment was examined. Ablation was effective, but the effects of E2 (5 mg) were confounded by treatment-induced ovulation in some animals. Two experiments were done to determine the effect of a reduced dose of E2 or the addition of progesterone (P4) in comparison with follicular ablation. Bison cows (n = 19), ≥3 years old, were scanned for 14 days to determine the mean and variance in the interval to follicular wave emergence (control phase). In Experiment 1, bison were assigned randomly to 2 groups: follicular ablation (n = 9) or 2 mg of E2i.m. (n = 10). In Experiment 2, the same bison were randomly assigned to 2 groups: follicular ablation (n = 9) or 2 mg of E2+ 100 mg of P4 i.m. (n = 10). Ablation involved transvaginal ultrasound-guided aspiration of all follicles ≥5 mm. Wave emergence was determined retrospectively by identification of the follicle destined to become dominant at an initial diameter of 4 to 5 mm, with a concurrent increase in the number of follicles ≥4 mm. The interval and variation in the interval to emergence of a new follicular wave was compared among the control phase and treatment groups by ANOVA. In Experiment 1, the interval to new wave emergence (mean ± SEM) was 4.9 ± 0.66, 1.1 ± 0.11, and 2.4 ± 0.47 days from the start of the control phase, follicular ablation, and E2 treatment, respectively (P < 0.001). The degree of synchrony (residuals) was 2.4 ± 0.36, 0.2 ± 0.09, and 1.2 ± 0.24 days for the control phase, follicular ablation, and E2 treatment, respectively (P < 0.001). Ovulation was detected in 1 bison treated with E2. In Experiment 2, the interval to new wave emergence (mean ± SEM) was 4.9 ± 0.66, 1.2 ± 0.15, and 2.9 ± 0.31 days from the start of the control phase, follicular ablation, and E2 + P4 treatment, respectively (P < 0.001). The degree of synchrony was 2.4 ± 0.36, 0.2 ± 0.08, and 0.7 ± 0.20 days for the control phase, follicular ablation, and E2 + P4 treatment, respectively (P < 0.001), and no ovulations were detected. In conclusion, follicular ablation, E2, and E2 + P4 treatments all shortened and decreased the variability in the interval to new wave emergence in bison, but follicular ablation consistently produced a quicker and more synchronous response. Supported by grants from the Advancing Canadian Agriculture and Agri-Food Fund (ACAAF), the Agri-Food Innovation Fund, Parks Canada, the World Wildlife Fund, and the Northwest Territories.

As part of a project involving reproductive biotechnology as a method of preserving Canada’s threatened wood bison population, an experiment was designed to test the effectiveness of steroid-induced ovarian synchronization and fixed-timed AI. The experiment was performed in the early ovulatory season (September) with female wood bison (4 years old, n = 13) and plains bison (2 years old, n = 4, and 8 years old, n = 3). Based on results of a preceding study, progesterone was combined with estradiol as a synchronization treatment to mitigate against untimely ovulation. The bison were blocked by subspecies and assigned randomly to a control group (no treatment; n = 10) or given estradiol 17β (2.5 mg) + progesterone (50 mg) in canola oil i.m. and a progesterone-releasing intravaginal device (Cue-mate™, Bioniche, Belleville, Ontario, Canada) on Day 0 (n = 10). On Day 8, the Cue-mate™ device was removed and PGF (500 mg Estrumate®, Mallinckrodt Vet GmbH, Friesoythe, Germany) was given to induce luteolysis. On Day 10, all bison were given 5 mg of LH (Lutropin®-V, Bioniche) and artificially inseminated 12 h later with semen collected and frozen previously from wood bison of the same herd. The ovaries were examined daily by transrectal ultrasonography beginning 5 days before treatment and thereafter until the first post-treatment ovulation. Ultrasonographic pregnancy diagnosis was done 30 days post-insemination. No differences were detected between wood and plains bison for any end point, and data were combined for further statistical analyses. Ovarian follicular wave emergence occurred on Day 4.1 ± 0.8 (mean ± SEM) and 4.1 ± 0.3 in the control and treatment groups, respectively (P = 99.3). The interval to new wave emergence was less variable in bison treated with estradiol + progesterone than in untreated controls (residuals, 0.7 ± 0.2 and 1.9 ± 0.5 days, respectively; P < 0.05). The interval from LH administration to ovulation was 2.7 ± 0.6 and 5.4 ± 1.9 days for the treatment and control groups, respectively, and was less variable in the treatment group than in controls (residuals, 1.2 ± 0.4 and 5.3 ± 0.8 days, respectively; P < 0.05). The diameter of the preovulatory follicle was not different between groups and was, on average, 15.2 ± 1.1 mm. Pregnancy was diagnosed in 3 bison in the treatment group and 2 in the control group. In conclusion, treatment with estradiol and progesterone effectively synchronized the interval to wave emergence, and subsequent LH treatment resulted in a synchronous ovulatory response necessary for fixed-time AI in bison. Although the pregnancy rate was modest, perhaps because of issues with semen quality, timing of AI, or quality of the ovulated oocyte, this represents the first report of pregnancy in bison from fixed-time insemination. Supported by grants from the Advancing Canadian Agriculture and Agri-Food Fund, the Agri-Food Innovation Fund, Parks Canada, the World Wildlife Fund, and the Northwest Territories.

The presence of an ovulation-inducing factor (OIF) in the seminal plasma of llamas and alpacas (reflex ovulators) and cattle (spontaneous ovulators) has been reported previously (Ratto MH et al. 2006 Theriogenology 66, 1102–1106). The presence of this protein in unrelated species supports the hypothesis that OIF is a conserved factor among species. The objectives of this study were to determine if OIF was present in equine and porcine seminal plasma, and whether the proportion of test animals (llamas) that ovulated in response to treatment with seminal plasma was related to dose. In Experiment 1, female llamas were assigned randomly to four groups (n = 8 or 9 per group) and treated intramuscularly with 1 mL llama seminal plasma (positive control), 3 mL equine seminal plasma, 3 mL porcine seminal plasma, or 2 mL saline (negative control). Ovulation and maximum corpus luteum diameter were compared using ultrasonography and confirmed with blood samples taken on Day 7 (Day 0 = day of treatment) to determine plasma progesterone concentration. The diameter of the preovulatory follicle at the time of treatment did not differ among groups. Equine seminal plasma induced ovulations in 3/8 (38%) llamas compared to 0/8 (0%) llamas treated with saline or porcine seminal plasma (P = 0.1). The proportion of females that ovulated was lower in the equine group (P < 0.01) compared with those animals treated with llama seminal plasma (9/9; 100%). Of the animals that ovulated, maximum CL diameter did not differ between llama and equine seminal plasma-treated groups (mean ± SEM; 11.1 ± 1.1, 11.5 ± 1.5, respectively). Similarly, progesterone concentrations were not different among llamas treated with llama seminal plasma or equine seminal plasma (mean ± SEM; 3.1 ± 0.4, 3.7 ± 1.2, respectively). The design of Experiment 2 was the same, but the dose of equine and porcine seminal plasma was increased to 8 mL and 10 mL, respectively. The proportion of females that ovulated was less (P < 0.05) in equine (2/9) and porcine (3/9) seminal plasma groups compared with the group treated with llama seminal plasma (9/9). There were no ovulations detected in llamas treated with saline (0/8). Although differences between equine, porcine, and negative control groups did not reach significance, results provide some evidence for the presence of OIF in equine and porcine seminal plasma. The effect of dose of equine and porcine seminal plasma is equivocal, suggesting that the concentration of OIF in the seminal plasma of these species may be very low and the optimal dose for inducing ovulation in test animals had not been reached. Research supported by the Natural Sciences and Engineering Council of Canada.