Folic acid or folate is a B-complex vitamin that works as a donor and acceptor of one‐carbon units. Thus, it is involved in the synthesis of nucleic acids (DNA) and amino acids (methionine). The name folic acid is deduced from folium (leaf in Latin), because this vitamin was originally isolated from spinach leaves.
Ruminal microorganisms from healthy cows produce enough amounts of folic acid to avoid deficiency. However, previous studies in dairy cows demonstrated that dietary supplementation of folic acid increases milk and milk protein yields. Since microbial degradation of supplemental folic acid is very extensive (more than 95%), rumen‐protected folic acid is usually used for feeding lactating cows.