Our team is also interested in the naturally occurring peptides released in bovine milk. We examined milk samples from six Holstein cows during their peak lactation period and identified hundreds of endogenous peptides in Holstein cow milk. Both the number and amounts of milk peptides present among the six cows were remarkably consistent, indicating a highly controlled enzymatic degradation system. Our team determined that the majority of the identified protein cleavages came from the action of a naturally occurring enzyme called plasmin, which is selectively pulled from the mother’s blood into her milk. Many of the identified peptides have beneficial functions. These peptides are inactive within milk proteins, but take on their respective functions when these proteins are cleaved by milk enzymes. Thus, in addition to providing building blocks for protein synthesis, the naturally occurring milk peptides likely provide consumers with many additional health benefits. We are continuing to map the bovine milk peptidome.