Use of purified FSH and LH for embryo production, cryopreservation by conventional freezing or vitrification and transfer of embryos in dairy ewes
and transfer of embryos in dairy sheep. Experiment I - For embryo production, thirty-one ewes were synchronized with
FGA (vaginal sponges, 40 mg, 9 d) and PGF2α (ICI; 50 μg, 7th d), and subdivided into three groups corresponding to the
following superovulatory treatments over 3 days with purified gonadotrophic preparations: A) control, FSH/LH ratio = 1
(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 – 1.7 –
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
of 5.0 – 1.0 – 0.3. On the 7th day after oestrus and mating, ovarian response and embryo production were evaluated.
Experiment II – Three freezing methods were evaluated based upon post-thaw embryo quality: CF) conventional slow
freezing by 1.5 M ethylene glycol (EG); V-1) one-step vitrification based on exposure of the embryos to one solution (EG
7.15 M + ficoll 2.5 mM); V-3) vitrification in three steps, corresponding to three solutions at increasing concentration of
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
directly plunged in liquid nitrogen. At thawing, embryo viability was evaluated on the basis of morphological features.
Experiment III – For embryo transfer, a total of 26 recipient ewes were synchronized with donors. On the 7th d from
oestrus, 11 recipient ewes received fresh embryos (Group FE – control) and 15 recipients received vitrified-thawed
embryos (Group VTE). Each recipient received 2 embryos. Superovulatory treatment B) significantly advanced the onset
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
10.8). Transferable embryos in Group B) (7.2) resulted similar to Group A) (5.3) and significantly (P<0.05) different when
compared to Group C) (3.2). V3-method resulted in the highest (P<0.01) transferable embryos (74.5%) compared to
CF- and V1-methods. After transfer, in FE and VTE recipient ewes were comparable in fertility rates (72.7 vs 73.3%;
P>0.05) and embryo survival (63.6 vs 56.7%; P>0.05). In conclusion, the results demonstrated that treatments B) and
C) did not improve superovulatory response compared to A); for embryo cryopreservation the V3 method can successfully
be used for embryo transfer in ewes.
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the Italian Journal of Animal Science [eISSN 1828-051X] is the official journal of the Animal Science and Production Association and it is published by PAGEPress®, Pavia, Italy. Reg. Pavia, n. 2/2010-INF. All credits and honors to PKP for their OJS.