The chicken cells eat on a cocktail of proteins, sugars and vitamins. The process also requires a substance to stimulate cell growth, often made from the blood of fetal cows.
Achieving this "fetal bovine serum" is a major obstacle to increasing production. It is commonly used in medical research – and it is expensive and controversial. It comes from slaughtered pregnant cows – which means that now some of the cell-based meats that Just, Inc. and other companies are not actually slaughter-free. Just, Inc. is working to create a new plant-based alternative.