Hippuric acid

Hippuric acid is an energy-rich substance subject to urinary excretion that (as the name, from Greek hippos for “horse”, already indicates) occurs only in horses. Aromatic compounds, primarily phenolic acids, are released in the gut from roughage cell walls. They are converted in the metabolism into hippuric acid and excreted as such in the urine. Depending on the crude protein content and the content of phenolic acids in the feed, more or less hippuric acid is formed.

As hippuric acid is very energy-rich, part of the total energy of a feed is therefore lost to the horse via hippuric acid in the urine (so-called renal energy losses). These losses, along with losses via intestinal gases, are taken into account when calculating the ME content (metabolisable energy) of a feed. The energy unit ME is therefore considerably more accurate than the unit DE according to GfE 2014.