Study summary · research use only
Effects of FSH commercial preparation and follicular status on follicular growth and superovulatory response in Spanish Merino ewes
Plain-language summary
Paraphrased from the published abstract below — not a verdict on whether anything works.
In this study of 24 Spanish Merino ewes, researchers compared how two commercial FSH products affected follicular growth and superovulatory response after estrus synchronization with 40 mg fluorogestone acetate sponges. Ewes received either 6 decreasing doses (4, 4, 3, 3, 2, 2 mg) of FSH-P or 6 doses of 1.25 mL of OVAGEN. FSH-P was associated with more new follicles (6.3 vs 4.8) and medium follicles (8.9 vs 6.6) than OVAGEN, but also more regressed follicles (5.9 vs 3.3) and more preovulatory follicles that did not ovulate (60 vs 42.4%). Ovulation rate on Day 7 did not differ between groups (6.3 vs 7.0 corpora lutea), and was related to small (2 to 3 mm) follicle counts at treatment start and follicles reaching 4 mm or more by estrus.
Abstract
Ovarian follicular development was characterized in 24 Spanish Merino ewes to study effects of the follicular status and the FSH commercial product used on follicular growth and subsequent superovulatory response. Estrus was synchronized using 40 mg fluorogestone acetate sponges. The superovulatory treatment consisted in 2 daily i.m. injections of FSH from 48 h before to 12 h after sponge removal. Sheep were assigned randomly to 2 groups treated with 6 decreasing doses (4, 4, 3, 3, 2, 2 mg) of FSH-P or with 6 doses of 1.25 mL of OVAGEN. Growth and regression of all follicles > or = 2 mm were observed by transrectal ultrasonography, and recorded daily from Day 6 before sponge insertion to the first FSH injection, and then twice daily until estrus was detected with vasectomized rams. Differences were detected in follicular development from the first FSH injection to detection of estrus (-48 to 36 h from sponge removal) between groups. Administration of FSH-P increased the appearance of new follicles with respect to OVAGEN (6.3 +/- 0.7 vs 4.8 +/- 0.4; P < 0.05), and the mean number of medium (4 to 5 mm) follicles (8.9 +/- 1.2 vs 6.6 +/- 0.9; P < 0.05). However, the mean number of follicles that regressed in size after sponge removal (5.9 +/- 0.4 vs 3.3 +/- 0.4) and the number of preovulatory sized follicles that did not ovulate (60 vs 42.4%) were also higher in FSH-P treated ewes (P < 0.05). So, finally, there were no differences in ovulation rate, as determined by laparoscopy on Day 7 after sponge removal, between ewes treated with FSH-P or OVAGEN (6.3 +/- 1.9 vs 7.0 +/- 1.7 CL). In all the ewes, the ovulatory response was related (P < 0.05) both to the number of small follicles (2 to 3 mm in diameter) present in the ovaries at the start of treatment with exogenous FSH and to the number of follicles that reached > or = 4 mm in size at estrus, despite differences in the pattern of follicular development when using different commercial products.
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