The researchers studied how different levels of serum in the culture medium affected the growth of buffalo embryo cells. They removed the outer layer of the embryos and placed them on feeder cells with varying amounts of serum. They found that using 20% serum led to better cell growth compared to 10% or 15% serum. Some cells formed structures similar to early embryos, but without all the necessary cell types. When these structures were further cultured, they did not develop into colonies.