The effect of laser-assisted incubation on bovine in vitro embryos.

INTRODUCTION: This paper aimed to enhance the hatching of bovine in vitro produced embryos by exploring their optimal LAH perforation/thinning pattern. METHODS: Ovaries were col-lected from an abattoir to obtain cumulus-oocyte complexes. After in vitro fer-tilization, 4-cell, 8-cell, morula, and blastocyst-stage embryos were allocated to experimental groups, and their hatching outcomes were compared following four Laser-Assisted Hatching (LAH) treatments, which aim to facilitate embryo hatching from the zona pellucida and subsequent implantation into the endo-metrium by creating small pores or thinning the zona pellucida. The treatments included removal of 1/4 of the zona pellucida, removal of 1/3 of the zona pellucida, thinning of 1/4 of the zona pellucida, and thinning of 1/3 of the zona pellucida. RESULTS: The results showed that: ① The hatching rate of 4-cell embryos with 1/4 zona removal was significantly higher than that of the control group (p < 0.01); ② the hatching rate of 8-cell embryos with removal of 1/3 of the zona pellucida was significantly higher than that of the control group (p < 0.01); ③ for morula-stage embryos, both 1/3zona removal and 1/3zona thinning resulted in significantly higher hatch-ing rates than the control (p < 0.01); and ④ the hatching rate of blastocysts with removal of 1/3 was significantly higher than that of the control group (p < 0.01). CONCLUSION: In conclusion, the most effective LAH treatments were 1/4zona removal for 4-cell embryos and 1/3zona removal for 8-cell, morula, and blastocyst-stage embryos, all of which yielded improved hatching rates.