Evaluation of mare oocyte collection methods and stallion sperm penetration of zona-free hamster ova.

The research study explores the effectiveness of two methods of extracting eggs (oocytes) from horse ovaries, and how successful stallion sperm is at penetrating eggs without a surrounding layer (zona-free) from hamsters. The observations showed that extracting eggs by rupturing follicles delivered higher quality oocytes. Additionally, they discovered that in vitro capacitated stallion sperm successfully fertilized three-quarters of the zona-free hamster eggs.

Comparison of Oocyte Collection Methods

• The researchers compared two methods of obtaining horse egg cells (oocytes) from the ovarian follicles of slaughtered mares – by aspiration of follicular fluid and by isolation and rupture of follicles.
• A total of 500 oocytes were taken from 162 mares via aspiration, whereas 120 oocytes were obtained by rupturing the follicles of 14 mares.
• Significantly more high-quality oocytes were obtained through follicle rupture – 89.2% of them were morphologically unchanged. In contrast, only 29.3% were unmodified when aspiration was utilized.

Stallion Sperm Penetration of Zona-Free Hamster Ova

• The researchers then tested the ability of stallion sperm to penetrate the zona-free hamster oocytes. This process is called in vitro capacitation.
• They prepared the spermatozoa by washing in a special solution (TCM-199) and preincubated it for 4 to 5 hours at a specific concentration.
• Out of a total of 305 hamster eggs fertilized by sperm from 8 different stallions, 77.8% penetration was confirmed. This was based on the presence of characteristic features of fertilization like the enlargement of sperm heads and the presence of male chromosomes (pronuclei) alongside associated tails.
• In a repeated test with sperm from one of the stallions eight months later, the penetration average was lower – 52.8%.
• In a set of control eggs that were incubated without the presence of sperm, spontaneous activation was observed, with female chromosomes (pronuclei) found in 12 out of 57.

This study provides a valuable understanding of the efficacy of different methods for oocyte collection in mares and how stallion spermatozoa function in the fertilization process with zona-free eggs. Such findings can be beneficial for improving assisted reproduction techniques in larger mammals.