Inconsistency of the superovulatory responses of donor hinds has been a general feature of all red deer MOET programs (Asher GW et al. 2000 Anim. Reprod. Sci. 59, 61-70). The development of the techniques has been by trial and error as there is usually a lack of basic information on which to base MOET protocols (Fennessy PF et al. 1994 Theriogenology 41, 133-138). The objective of this study was to understand follicle development during a superovulatory treatment in order to improve ovulation rates and quantity of transferable embryos produced. During the breeding season, 10 mature (3-5 years old) red deer hinds were synchronized receiving an intravaginal sponge containing 100 mg of medroxiprogesterone acetate for 13 days, with device replacement on Day 11. Four days prior to the beginning of the FSH treatment, 0.5 mg of estradiol benzoate (Syntex SA, Buenos Aires, Argentina) was given i.m. to synchronize the follicular wave. Superovulation was conducted with a total dose of 120 mg of NIH-FSH-P1 (Folltropin®-V, Bioniche Animal Health, Belleville, Ontario, Canada) given i.m. in 4 equal doses of 30 mg every 24 h, from Day 11 to 14. Forty-eight hours after sponge withdrawal, 0.84 mg of buserelin acetate (Receptal®, Intervet, Boxmeer, the Netherlands) was injected i.m. to stimulate and synchronize ovulations. Ovarian scanning was performed by transrectal ultrasonography using a multifrequency linear transducer (Tringa Linear, Esaote Pie Medical, Genoa, Italy) on Days -1, 0, 1, 2, 3, 4, 5, and 6, Day 0 being the day of sponge withdrawal. The diameters of all follicles ≥3 mm were measured and their 3-dimensional position recorded to determine growth and ovulation. The average ovulation rate was 10.8 ± 1.6. The distribution of ovulations was 9.3, 31.5, 24.1, 22.2, 9.2, and 3.7% at 24, 48, 72, 96, 120, and 144 h after sponge withdrawal, respectively. The proportion of follicles that did not ovulate during the period of this study was 16.9%. The proportion of ovulated follicles according to their diameter was 9.3, 68.5, and 22.2% for 3 mm, 4 to 5 mm, and ≥6 mm, respectively, and were during the 24- to 96-h period for the first 2 follicles categories and after 96 h for the last category. This study showed a great variability of ovulations in the superovulatory protocols routinely used in red deer donor hinds. Improvement of the hormone treatment to induce a greater degree of ovulation synchrony (within 72 h after progesterone device withdrawal) would increase the fertilization rates and the quantity of transferable embryos produced in red deer MOET programs.
Table 1.Mean (±SEM) ovulation rate and number of follicles recorded at each ultrasonography day before and after sponge withdrawal
Superovulation in red deer (Cervus elaphus) and Pere David's deer (Elaphurus davidianus), and fertilization rates following artificial insemination with Pere David's deer semen