Authors
Abstract
ABSTRACT: The purpose of this study was to evaluate ovarian response, using transrectal ovarian ultrasonography, after two injections of Prostaglandin F2α (PGF2α) given at different intervals. Fourteen Bergamasca ewes were examined during the breeding season, and they were injected with an intramuscular dose of a PGF2α analogue. Ewes were randomly allocated to two groups (n = 7) which received PGF2α for 7 days (PG7) or 9 days (PG9) after ovulation (when the dominant follicle of wave 2 was expected to be in the growing and plateau phase, respectively). The ovaries were examined daily with transrectal ultrasonography Aloka 500® with 7.5 MHz linear array transducer, which started 1day prior to the second PG injection and ended 10 days after ovulation in both groups. Jugular vein blood samples were collected daily for progesterone assay. Plasma P4 concentration were lower in PG7 that in PG9 immediately before the PGF2α treatment (4.10±0.17 vs 4.91±0.29 ng/mL, respectively; P<0.05). Mean maximum diameter size attained by the dominant follicle of wave 2 tended to be larger in the PG7 group, compared with PG9 (5.5±0.19 vs 4.29±0.26 mm; P<0.05). The number of small follicles (2-2.5 mm) was greater (4.57±0.78 vs 8.42±1.36) at day 6, for PG7 and PG9, respectively, whereas no changes were observed in medium follicles. The proportion of large follicles (4 mm) increased after luteolysis. Values were lower for ewes treated with PG7, whereas values were more stable over time for ewes treated with PG9. In conclusion, ewes with rapid and complete luteal regression, ovulation occurred from the dominant follicle of wave 2 when the females were treated on days 7 and 9.
Keywords:
References
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