The researchers wanted to see how well injecting sperm into pig eggs worked, and if adding extra treatments could help. They found that using a combination of sperm injection and electrical activation led to better fertilization and embryo development. However, adding more treatments didn't make a big difference. They also discovered that most eggs formed a female pronucleus after injection, but some failed to form a male pronucleus, leading to fertilization failure. This failure of male pronucleus formation was the main reason why some pig embryos didn't develop properly.