Moment of addition of LH to the culture medium improves in vitro survival and development of secondary goat pre-antral follicles

The present study investigated the effects of time of addition of luteinizing hormone (LH) to culture medium on the in vitro development of caprine pre-antral follicles. Pre-antral follicles (≥ 150 μm) were isolated from fragments of the goat ovarian cortex and individually cultured for 18 days in the absence (control) or presence of 100 ng/ml LH, added on days 0, 6 or 12 of culture. Follicular development was assessed based on antral cavity formation, increased follicular diameter as well as follicular and fully grown oocyte (>110 μm) viability. The results showed that after 18 days of culture, the percentage of surviving follicles in the control treatment was significantly lower when compared to other treatments (p < 0.05). There were no significant differences in antrum formation, follicular diameter and oocyte viability. The addition of LH at D6 of culture significantly increased the rates of oocytes ≥ 110 μm and the resumption of meiosis (p < 0.05). In contrast, when LH was added at the onset of culture, only germinal vesicle oocytes were obtained. In conclusion, the moment of addition of LH to the culture medium affects the performance of in vitro culture of caprine pre-antral follicles. The addition of LH to the medium from day 6 of culture onward improved the rates of follicular survival, as well as the ability of oocytes to resume meiosis. However, prolonged exposure to LH (addition at the onset of culture onward) showed detrimental effects for the meiotic resumption.