Superovulation and egg transfer in the ewe
Reproduction nutrition development (Print)
102 Prealpes du Sud donor ewes were superovulated by a treatment with vaginal sponges impregnated with 40 mg of FGA. When the sponges were withdrawn at 14 days, follicular maturation was stimulated in these ewes with 12 mg of porcine pituitary extract (pFSH). The recipient ewes were treated i.m. with 500 IU of PMSG. Different batches of pFSH (batch pFSH1/Group A ; batch pFSH2 : groups B and C) were used ; a total of 12 mg was given in 4 injections of 3 mg each (groups A and B) or in decreasing
... ) or in decreasing doses of 5, 3, 2, and 1 mg (group C). The embryos were recovered at D6 and transferred after 1 or 5 h of storaqe in medium 199 or medium B2 (Ménézo, 1976) + 10 % FCS at either 37 or 20 °C (B only). Surgery was used to recover the embryos and place them (one per uterine horn) in the recipients. pFSH1 induced estrus 24 h after sponge withdrawal in 100 % of group A ewes. When the LH level was lower (pFSH2 ; groups B and C), only 62.5 % of the ewes came on heat at 24 h. pFSH2 induced 8.1 corpora lutea per ewe (groups B and C) vs 4.6 in group A (pFSH1) and twofold more viable embryos were recovered in groups B and C than in group A (6.1 vs 2.7). In relation to the number of corpora lutea, 59, 69 and 80 % of viable embryos were recovered in groups A, B, and C, respectively. There was a positive correlation between the number of corpora lutea and the number of morulae recovered. The regression line of each group has been plotted. One or 5-h storage in medium B2 at 37 °C gave 25 and 17 % of ewes lambing with an embryonic survival rate of 17.6 and 10.5 %. Storage in medium 199 gave better results only for 1-h storage (60 and 47 %) ; results after 5 h were comparable to those obtained with B2 (25 and 17 %l. When the temperature was lowered to 20 °C (medium B2) after 1 and 5 h of storage, 66 % of these ewes lambed and embryonic survival rose to 47 % instead of 14 %. The origin of the pituitary extract determined whether or not good superovulation was obtained. However, the response varied greatly from one ewe to another. Embryonic storage at 37 °C was limited ; 20 °C markedly improved embryonic survival after transfer. Introduction.