Abstract
Fraction V bovine serum albumin (BSA) was dissolved in 5% formic acid and filtered through a molecular filter with a cutoff of MW 10,000. The freeze-dried filtrate stimulated increased cell division of cultured rabbit morulae to blastocysts (up to 8-fold increase in cell number) and increased blastocyst expansion (> 2-fold). Some samples of commercial BSA evidently contain an embryonic growth factor of a low MW.