Use of purified FSH and LH for embryo production, cryopreservation by conventional freezing or vitrification and transfer of embryos in dairy ewes

• Main Authors: Giovanni Martemucci, Angela Gabriella D’Alessandro
• Format: Article
• Language: English
• Published: Taylor & Francis Group 2010-01-01
• Series: Italian Journal of Animal Science
• Subjects: Ewes, In vivo embryo production, Embryo freezing, Embryo transfer
• Online Access: http://www.aspajournal.it/index.php/ijas/article/view/146

Three experiments were carried out with the aim of evaluating the efficiency of techniques of in vivo production, storage<br />and transfer of embryos in dairy sheep. Experiment I - For embryo production, thirty-one ewes were synchronized with<br />FGA (vaginal sponges, 40 mg, 9 d) and PGF2&alpha; (ICI; 50 &mu;g, 7th d), and subdivided into three groups corresponding to the<br />following superovulatory treatments over 3 days with purified gonadotrophic preparations: A) control, FSH/LH ratio = 1<br />(250 IU p-FSH : 250 UI p-LH); B) FSH/LH ratio = 2 (250 IU p-FSH : 125 IU p-LH) and daily FSH/LH ratio of 3.4 &ndash; 1.7 &ndash;<br />0.8 in the 3 days of treatment, respectively; C) FSH/LH ratio = 2 (250 IU p-FSH : 125 IU p-LH) and daily FSH/LH ratio<br />of 5.0 &ndash; 1.0 &ndash; 0.3. On the 7th day after oestrus and mating, ovarian response and embryo production were evaluated.<br />Experiment II &ndash; Three freezing methods were evaluated based upon post-thaw embryo quality: CF) conventional slow<br />freezing by 1.5 M ethylene glycol (EG); V-1) one-step vitrification based on exposure of the embryos to one solution (EG<br />7.15 M + ficoll 2.5 mM); V-3) vitrification in three steps, corresponding to three solutions at increasing concentration of<br />glycerol (GLY) and EG (GLY 1.4 M; GLY 3.4 M + EG 1.4 M; GLY 4.6 M + EG 3.4 M). V-1) and V-3) frozen embryos were<br />directly plunged in liquid nitrogen. At thawing, embryo viability was evaluated on the basis of morphological features.<br />Experiment III &ndash; For embryo transfer, a total of 26 recipient ewes were synchronized with donors. On the 7th d from<br />oestrus, 11 recipient ewes received fresh embryos (Group FE &ndash; control) and 15 recipients received vitrified-thawed<br />embryos (Group VTE). Each recipient received 2 embryos. Superovulatory treatment B) significantly advanced the onset<br />of oestrus compared to the control (27.3 vs 34.7 h; P<0.05). Ovulation rate did not differ among the groups (6.5 to<br />10.8). Transferable embryos in Group B) (7.2) resulted similar to Group A) (5.3) and significantly (P<0.05) different when<br />compared to Group C) (3.2). V3-method resulted in the highest (P<0.01) transferable embryos (74.5%) compared to<br />CF- and V1-methods. After transfer, in FE and VTE recipient ewes were comparable in fertility rates (72.7 vs 73.3%;<br />P>0.05) and embryo survival (63.6 vs 56.7%; P>0.05). In conclusion, the results demonstrated that treatments B) and<br />C) did not improve superovulatory response compared to A); for embryo cryopreservation the V3 method can successfully<br />be used for embryo transfer in ewes.