Production and lambing rate of blastocysts derived from in vitro matured oocytes after gonadotropin treatment of prepubertal ewes

The aim of this study was to evaluate
the effect of gonadotropin treatment on thein vitromaturation, blastocyst production, and developmental
potential to term of oocytes collected from Sardinian
neonatal and prepubertal ewes at 4 to 6 wk of age.
Cumulus-oocyte complexes were recovered at 24 h
after withdrawal of a 1/6th size progestagenated
pessary from the donors, of which each received 120
IU FSH/LH and 400 IU PMSG in a single dose 36 h
before sponge removal. Treated donors produced a
greater ( P < .01) number of oocytes per animal (86.2
± 7.9) compared with slaughterhouse (untreated)
prepubertal ewes (55.5 ± 6.1) of the same age or with
treated neonatal ewes (6.1 ± 0.7) 10 d old. During
oocyte maturation, there were no differences in the
percentage of germinal vesicle break-down (78.08 vs
74.24), metaphase I (89.13 vs 87.18), and metaphase
II (77.91 vs 76.38) when evaluated after 8, 14, and 24
h of maturation, respectively, between oocytes from
treated and slaughterhouse (untreated) prepubertal
ewes. The embryo cleavage (71.1 vs 73.7) and
blastocyst rates (22.2 vs 19.8) were similar in the
treated and the untreated prepubertal ewes after
transfer ofin vitromatured oocytes into ligated
oviducts of temporary recipients. Thein vitroviability
rates of vitrified blastocysts (81.2 vs 76.9) and thein
vivosurvival rates (46.1 vs 50.0) of embryos derived
fromin vitromatured andin vivofertilized oocytes
showed no difference. The data suggest that
gonadotropin treatment increases oocyte production
per animal but has no effect on oocyte quality because
embryo production and lambing rates of blastocysts
derived fromin vitro maturedoocytes were not
markedly different from those derived from untreated
prepubertal ewes of the same age.