Zinc Chloride Supplemented during Ovarian Tissue Vitrification Improves In Vitro Follicle Development and Fertilization in Pigs

Ovarian tissue vitrification is a promising method to preserve follicles and gametes, but can be improved with mineral supplementation to the vitrification medium. The objective of this study was to determine the effects of supplementing 0.5 mg/mL zinc chloride to the media during cryopreservation of pig ovarian tissue. After thawing, the following criteria were evaluated: (1) follicular development and damage, (2) in vitro fertilization (IVF) characteristics, and (3) embryonic development. The number of damaged antral follicles (72.0 ± 3.8%) was less (p < 0.05) in ovarian tissue vitrified in media supplemented with zinc chloride compared to those not supplemented with zinc chloride (86.7 ± 4.1%). Oocytes obtained from the antral follicles on ovarian tissue vitrified in media supplemented with zinc chloride had less (p < 0.05) polyspermic penetration and higher (p < 0.05) male pronuclear formation during IVF than oocytes obtained from ovarian tissue not supplemented with zinc chloride. There were no statistical differences in embryonic development rates. Based on these results, supplementing zinc chloride during the vitrification protocol improves follicular development and subsequent IVF in pigs.