Ammonium fumarate is a compound with formula (NH4)2(C2H2(COO)2). It is the ammonium salt of fumaric acid. As a food additive, it has the E number E368.
In theory, ammonium fumarate could be used as a food additive to corn fed to cows, but an experiment with steers found that the additive with palm oil, "did not affect animal performance, carcass characteristics, or economic return."
References