Maximizing embryo production in endangered sheep breeds: in vitro procedures to complement in vivo techniques | La producción de embriones in vitro como complemento de las técnicas de producción in vivo al servicio de la conservación de razas ovinas en peligro de extinción
2011
Forcada, F. | Buffoni, A. | Abecia, J.A. | Asenjo, B. | Palacín, I. | Vázquez, M.I. | Sánchez Prieto, L. | Casao, A.
This study investigated the use of previously superovulated ovaries as a source of oocytes, assessing the competence of them for in vitro embryo production. Two superovulatory treatments were performed: eCG plus FSH in a single dose (S) or the conventional protocol of six decreasing doses of FSH (D). Thirty donor ewes of the endangered Ojalada breed were given either the simplified (group S; n=15) or the decreasing-dose (group D; n=15) treatments three times at intervals of >=50 d. Ovaries were recovered on day 7 after the estrus following the third treatment, and the oocytes were collected to assess in vitro maturation, fertilization, and development to the blastocyst stage. Oocytes from non-previously superovulated ewes recovered at a local slaughterhouse served as the Control group (C). The two superovulatory treatments and the control group did not differ in the mean number of oocytes selected for maturation (7.1+/-1.2 and 8.5+/-1.5 per ewe, and 4.5+/-0.3 per ovary in the D, S, and C groups, respectively). The oocytes recovered from ewes in Group D (87.5%) had a significantly (P<0.05) higher maturation rate than did those recovered from ewes in group S (75%) or the C group (75.4%). Although the oocytes from non-superovulated ewes had a higher (P<0.05) fertilization rate (98.6%) than did those derived from superovulated ovaries (94% and 94.6% in the D and S groups, respectively), the three groups did not differ in their blastocyst rates and the total number of cells in in vitroproduced blastocysts. In the two superovulated groups, 1.7 (D) and 1.8 (S) in vitro-produced blastocysts were generated per ewe, which indicates that it is feasible to combine in vivo and in vitro techniques to maximize embryo production in endangered sheep breeds.
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