Nerve growth factor (NGF) is a neurotrophic factor that is essential for the maintenance of peripheral and central neurons. While importance of such physiological activities as well as the potential of it as a stress marker in Equus caballus has been implicated, the sequence of equine NGF remained unknown. In this study, we identified the sequence of equine NGF from the mRNA expressed in the peripheral blood in seven Thoroughbreds and three warmblood horses. There were no polymorphisms among samples analyzed, and the homology is more than 90% in comparison to human, mouse, rat, dog, and cow. When the sequence corresponding to the biologically active beta-nerve growth factor was expressed in CHO-K1 cells, they were stained with an anti-NGF antibody that recognizes human NGF. Thus, it provides a rationale for using antibodies that react to other species' NGF to measure the equine NGF for further studies. (C) 2016 Elsevier Inc. All rights reserved.