Effects of different doses of estradiol benzoate used in a cervical relaxation protocol on the success of non-surgical embryo recovery and luteal function in superovulated ewes.

This study investigated the effectiveness of different doses of estradiol benzoate (EB) to promote cervical relaxation and their effects on luteal function and outcomes of non-surgical embryo recovery (NSER) in sheep. Multiparous (MULT) and nulliparous (NULL) crossbred Lacaune X Santa Inês ewes were superovulated and naturally bred. Seven days after progesterone withdrawal, females were randomly assigned to one of three distinct cervical relaxation protocols, consisting of i.m. treatment with 37.5 µg d-cloprostenol and different doses of EB: 0.0 mg (0.0EB group; n = 3 NULL and 14 MULT); 0.5 mg (0.5EB group; n = 4 NULL and 12 MULT) or 1.0 mg (1.0EB group, n = 6 NULL and 11 MULT) 16 h before NSER. All ewes received 50 IU of oxytocin 20 min before NSER (D17). Blood samples were collected and ultrasound exams (B-mode and color Doppler) were performed at two timepoints: immediately before d-cloprostenol and EB treatments and prior to NSER. Estrous behavior, corpora lutea count and NSER success outcomes were not affected by EB treatments nor parity (P > 0.05). Embryo recovery rate was greater for ewes in the 0.5EB group and in the NULL ewes (P < 0.05). Ovarian biometrics differed between the two evaluation timepoints in all groups (P < 0.05). Plasma estradiol increased over time, reaching a significant greater level in 1.0EB ewes compared to controls on D17 (P < 0.05), whereas progesterone concentrations decreased over time in all groups (P > 0.05). In conclusion, treatments did not affect NSER success but they did affect luteal function by altering P4 and E2 concentrations. Therefore, the NSER technique can be successfully performed in ewes with or without prior treatment with EB.

Single dose of 300 IU hCG in the early luteal phase in superovulated ewes: Effects on corpora lutea, progesterone profile, and embryo recovery.

This study aimed to evaluate the effects of hCG treatment during the early luteal phase on ovarian function, progesterone profile, and embryo yield in superovulated ewes. Superovulated sheep were randomly assigned to receive 300 IU hCG i.m. (GhCG, n = 24) or not (GControl, n = 25) at 96 h after the removal of the progesterone (P4) device (D13). Non-surgical embryo recovery (NSER) was performed eight days after P4 withdrawal. Ultrasound evaluations were performed on D13, D14, D16, and D17. Blood samples were collected on D14, D16, and D17. Superovulation scores were recorded based on the number of corpora lutea (CL) as follows: 1 (≤ 2), 2 (3-5), 3 (6-8), and 4 (≥ 9). NSER efficiency, superovulation response, and luteal tissue area were similar in both groups (P > 0.05). Structural luteolysis tended to be higher in GControl (P = 0.07; 47.0 %) while functional luteolysis was similar in both groups (P > 0.05; 0.0 % and 5.9 %). The recovery rate was greater (P < 0.05) in GhCG (89.8 %) compared with GControl (71.0 %), with similar overall ova/embryo numbers observed for both groups (P > 0.05). GhCG showed a higher concentration of animals with a superovulatory response score of 4 (54.5 %; P < 0.05) compared with the lowest scores. Plasma progesterone on D16 was higher (P < 0.05) in GhCG ewes (11.1 ± 1.5 vs 6.9 ± 1.5 ng/mL). In conclusion, the hCG treatment improved circulating P4 and embryo recovery rate, tended to maintain luteal functionality, and thus constitutes an additional tool for improving embryo yield in superovulated ewes.

Effects of d-cloprostenol administrations with 7.5 and 11.5-day intervals between administrations on pregnancy rates after artificial insemination in estrous cyclic dairy goats.

This study was conducted to evaluate effects of two administrations of d-cloprostenol at different intervals to synchronize the time of estrus and ovulation among estrous cyclic goats. In Experiment 1, 32 does were treated with 30 µg d-cloprostenol at 7.5 (T7.5, n = 16) or 11.5-day (T11.5, n = 16) intervals. In Experiment 2, the same treatments were administered and there was AI of the does (T7.5, n = 40 and T11.5, n = 38). In Experiment 1, ultrasonic assessments of ovaries were conducted at the time of the second administration of d-cloprostenol, every 12 h until detection of ovulation, and 7 days after estrous onset to detect the corpora lutea, as well as for pregnancy diagnosis 40 days after AI. In Experiment 1, the estrous response (90.6%, 29/32) was similar (P > 0.05) in both groups. Diameter of the largest follicle at the time of administration of the second dose was larger (P = 0.01) in the T7.5 than T11.5 group (7.0 compared with 5.7 mm), while the values for ovarian variables were similar (P > 0.05). In Experiment 2, the greatest (P < 0.001) synchrony in timing of initiation of estrus in does (T7.5 = 83.3% and T11.5 = 50.0%) occurred after the second day (36-48 h). The pregnancy rate tended (P = 0.0836) to be greater for does in the T7.5 (71.4%, 40/56) than T11.5 (55.6%, 30/54) group. With use of both protocols, there were acceptable estrous synchronization and pregnancy rates in estrous cyclic dairy goats.