Submission Number: LUI-4-10-3

Abstract Number: 295

EFFECT OF DAY OF PROSTAGLANDIN F₂ TREATMENT ON FOLLICULAR POPULATION IN BERGAMASCA EWES.

Luis Fernando Uribe-Velásquez ¹, Eunice Oba ¹, Lida Constanza Lara-Herrera ², Maria Inês Lenz Souza ¹, Hooverman Villa-Velásquez ², Lúcia Aparecida Trinca ³ and Edgardo Rubianes ⁴

Dept. Radiology Veterinary and Animal Reproduction, UNESP, Botucatu, São Paulo, Brazil ¹
Faculty of Medicine, UNESP, Botucatu, São Paulo, Brazil ²
Institute of Bioscience, UNESP, Botucatu, São Paulo, Brazil ³
Dept. of Animal Physiology, Universidad de la República, Montevideo, Uruguay ⁴

Abstract:
Day of the cycle on which PGF₂ was given influenced intervals to onset of estrus and the preovulatory surge of LH. Fourteen Bergamasca ewes were examined during the breeding season. All ewes were injected with an i.m. dose of PGF₂ analogue. Ewes were randomly allocated to two groups (n = 7) which received PGF₂ 7d (G7) or 9d (G9) after ovulation (when the dominant follicle of wave 2 was expected to be in the growing and plateau phase, respectively). Ovaries were examined daily with transrectal ultrasonography Aloka 500 with 7.5 MHz linear array transducer. Jugular vein blood samples were collected daily. The viable dominant follicle at the time of luteolysis became the ovulatory follicle. Serum P4 concentration were lower in G7 that in G9 immediately before PGF₂ treatment (4.100.17 vs. 4.910.29 ng/ml., respectively; P<0.05). Mean maximum diameter size attained by the dominant follicle of wave 2 tended to be larger in the group treated in G7 when compared with G9 (5.50.5 vs. 4.290.3 mm; P<0.05). There was effect of day with total follicles (P<0.001). Number of small follicles (2-2.5 mm) was greater (4.570.78 vs. 8.421.36) at day 6, for G7 and G9, respectively, whereas no changes were observed in medium follicles (3-3.5 mm) between groups treated. The proportion of large follicles (4 mm) increased after luteolysis. Values were lower for ewes treated on G7, whereas values were more stable over time for ewes treated on G9. In conclusion, follicular dynamics were altered by treatment with PGF₂ but no much different from the way they were altered by luteal regression at the end of an estrous cycle. In ewes with rapid and complete luteal regression, ovulation occurred from the dominant follicle of wave 2 in all ewes treated on days 7 and 9. Supported by FAPESP Sao Paulo Brazil. .

Keywords: Ewes, Synchronization, Follicles, Ultrasonography

This abstract is being presented at: 8:00 AM in session:
Follicular Development II