Ultrasound and endocrine evaluation of the ovarian response to a single dose of 500 IU of eCG following a 12-day treatment with progestogen-releasing intravaginal sponges in the breeding and nonbreeding seasons in ewes

• Published in: Theriogenology 2004-01, Vol.61 (2), p.311-327
• Main Authors: Barrett, D.M.W, Bartlewski, P.M, Batista-Arteaga, M, Symington, A, Rawlings, N.C
• Format: Article
• Language: English
• Subjects: Anestrus - drug effects; Animals; Antral follicles; Breeding; Corpus Luteum - physiology; eCG; equine chorionic gonadotropin; Estradiol - blood; Estrus Synchronization; Ewes; Female; Follicle Stimulating Hormone - blood; follicular development; Gonadotropins, Equine - administration & dosage; Ovarian Follicle - drug effects; Ovarian Follicle - physiology; Ovary - diagnostic imaging; Ovary - drug effects; Ovary - physiology; Ovulation; Progesterone - blood; Progestins - administration & dosage; Progestogen sponge; Seasons; Sheep; Ultrasonography; Ultrasound
• ISSN: 0093-691X; 1879-3231
• DOI: 10.1016/S0093-691X(03)00215-2

A standard dose of 500 IU of eCG is commonly given to progestogen pre-treated anestrous ewes for induction of estrus. Twelve seasonally anestrous and 12 cyclic Western White Face ewes were treated for 12 days with intravaginal sponges impregnated with medroxyprogesterone acetate (MAP). In trials in both the breeding and nonbreeding seasons, six randomly selected ewes were given 500 IU of eCG at sponge removal to determine the effects of low dose of eCG on ovarian antral follicular dynamics and ovulation. Ultrasound scanning and blood sampling were done daily. Treatment with eCG did not have marked effects on antral follicular growth. All ewes ovulated, except for five of six control anestrous ewes. Luteal structures and progesterone secretion were confirmed in all but the control anestrous ewes. In the breeding season, peak progesterone concentrations were greater ( P