Donkey serum is used as a component of bioassays, immunoassays or enzyme assays. Donkey serum provides a broad spectrum of macromolecules, carrier proteins for lipoid substances and trace elements, attachment and spreading factors, low molecular weight nutrients, and hormones and growth factors that promote cell growth and health. Donkey serum is available as a sterile preparation for use as a cell culture supplement. Additionally sold as 100 mL unit.