Abstract
This study investigates bromine (Br) concentration and its relationship with iodine concentration in serum samples of 86 horses. The mean serum Br concentration in horses pastured on green grass near the seashore was significantly higher (P<0.001) than that in horses pastured in a sand paddock. A significantly negative correlation (r=-0.479, P<0.01) between the serum Br and iodine concentrations was evident in the horses that pastured on green grass. The concentrations of several elements such as sodium and potassium were virtually constant in the serum. In addition, there were elements present below the detection limit of the analytical instruments used. In contrast, it was suggested that geological differences have a marked influence on serum Br concentrations in animals. Thus, we hypothesized that serum Br concentration in horses is a possible indicator reflecting geological differences.