Adult follicular fluid supplementation during in vitro maturation improves the developmental competence of prepubertal lamb oocytes

Oocytes from prepubertal lambs have lower developmental ability than that from adult ewes. Follicular fluid (FF) provides an important microenvironment for oocyte development and maturation in vivo. The aim of this study was to examine the effects of FF supplemented during in vitro maturation (IVM) on the developmental competence of prepubertal lamb oocytes. FF was collected from follicle-stimulating hormone (FSH) stimulated adult ewes or 4‒6-week-old lambs or abattoir-derived adult ovaries. The FF was supplemented to the control IVM medium, TCM199 containing 20% estrus sheep serum and hormones. It was found that the lamb oocytes matured in medium supplemented with 20% or 30% adult FF from FSH-stimulated ewes yielded significantly higher blastocyst rates than that from the control medium, or medium supplemented with 10% adult FF or 20% lamb FF (43.5%, 37.9% vs. 28.4%, 29.7%, 27.6%, P < 0.05). However, when adult oocytes were matured in medium supplemented with 20% adult FF, their cleavage and blastocyst development were similar to that of those matured in control medium. Addition of 20% adult FF from abattoir-derived ovaries to IVM medium also significantly increased the blastocyst formation of lamb oocytes when compared to that from the medium without FF supplementation. The blastocyst development did not differ between the groups of FF from abattoir-derived ovaries and from FSH-stimulated ewes (38.2% vs 43.1%, P > 0.05). A total of 146 blastocysts derived from different groups of lamb oocytes were transferred into 76 synchronized recipients, of which 50% were pregnant and 38.2% lambed. These results suggest that supplementing IVM medium with adult FF has beneficial roles on the developmental competence of prepubertal lamb oocytes.