The liquid in which the material is stored also is important. For example, freezing removes some chemicals from the membrane that surrounds the sperm cells from poultry. Those compounds had been important. They helped the sperm cell recognize an egg. Adding certain sugars and lipids to the solution in which bird sperm are stored may replace the lost chemicals, Long says. Altering the protective fluid and freezing solution also may improve a sperm cell’s survival — and fertility. Long’s team reported promising research with turkey sperm in December 2013 and again in June 2014 in the journal Cryobiology.