What it is
The first milk after a calf is born, sold as a powdered supplement on the strength of its immune proteins.
Why your biology objects
A genuine animal-derived whole substance — ~70–80% of its protein is immunoglobulins (IgG), plus lactoferrin and growth factors. The honest caveat: whether oral IgG and growth factors survive digestion to act *systemically* is unsettled, so the supplement claims outrun the evidence. Real first-milk is food; the marketed powder earns the asterisk.