Dysmorphic Goat Oocytes Showed Poor Embryo Developmental Capacity Following Intracytoplasmic Sperm Injection

ABSTRACT: Embryo developmental competence of dysmorphic goat oocytes recovered from abnormal ovaries was evaluated following intracytoplasmic sperm injection (ICSI). Cumulus-oocyte complexes (COCs) were obtained by slicing of abattoir-derived goat ovaries and categorized according to morphology of the ooplasm into four groups as normal, paler, oocyte with big fat globules (BFG) and oocyte with darker zone (DZ). The COCs were subjected to in vitro maturation (IVM) in presence of CO2 (5%) at 35-38°C for 27 hours (h). The ICSI was performed with immobilized sperm on the lid of a culture dish (35 mm) under an Olympus inverted microscope fitted with Narishige micromanipulators. Injected oocytes were cultured for <192 h in modified synthetic oviductal fluid (mSOF) medium in CO2 incubator. The maturation rates (mean±SEM) were 54.6±2.7, 56.7±4.9, 69.0±6.2 and 73.7±4.2% (P<0.05) for paler oocyte, oocyte with BFG, oocytes with DZ and normal oocytes, respectively. No significant difference was found between dysmorphic and normal oocytes in fertilization and cleavage rates. However, dysmorphic oocytes were arrested or degenerated at around 5-to 8-cell stage; whereas morula (12.6%, P<0.05) were obtained from normal oocytes. In conclusion, dysmorphic oocytes were less competent than normal oocytes in terms of embryo developmental capacity after ICSI in goat. 

Keywords: Goat, COCs, oocyte, ooplasmic dysmorphism, IVM, ICSI, embryo