The concentration of iodine in horse serum and its relationship with thyroxin concentration by geological difference

Abstract

In this study, iodine and thyroxin (T4) concentrations in the serum of 69 horses were investigated. Higher iodine concentrations were obtained from the horses housed in Chiba Prefecture. In contrast, T4 concentrations of horses at Shizuoka Prefecture were higher than those of horses at Chiba Prefecture. There was a significant correlation (r = 0.643, P < 0.001) between the iodine and T4 concentrations of horses at Saitama and Shizuoka prefectures. Although a significant correlation (r = 0.794, P < 0.001) was also observed in the investigation of all horses at Chiba Prefecture, the distribution area of the data was separated from the data of horses housed in Saitama and Shizuoka prefectures. A higher iodine concentration in the environment is expected in the sampling area at Chiba Prefecture. Thus, it was suggested that the concentrations of iodine in the serum of horses are influenced by geological differences. It was thought that equine serum is a useful sample for monitoring.

Serum bromine concentrations in horses in Japan

“…In our previous report [ 9 ], a higher mean serum iodine concentration was obtained in horses housed in the equestrian club in Chiba 1 (mean; 29.33 µ g/ l ). The mean serum iodine concentrations were found to be in the order of Chiba 1 >Chiba 2 =Chiba 3 =Yamanashi (newly added data in the present study, 23.80 ± 1.01 µ g/ l ) >Saitama =Shizuoka (including Shizuoka-a and Shizuoka-b in the present study) [ 9 ]. In contrast, this study showed an opposite trend for Br compared with that for iodine.…”

“…Shizuoka-a, horses pastured on green grass; Shizuoka-b, horses pastured in a sand paddock. The iodine concentrations in horses from Shizuoka, Chiba and Saitama were reported in another investigation [ 9 ]. ).…”

“…The mean Br concentration of Shizuoka-b and its relationship with serum iodine in the three nonpastured horses in the Shizuoka Prefecture validated our hypothesis. Alternatively, as discussed in our previously published paper [ 9 ], horses housed in Chiba 1 were provided feed supplemented with seaweed. Depending on its type, seaweed is known to contain Br of various concentrations [ 15 ].…”

“…, serum samples were collected from six equestrian clubs in four prefectures located on the main island of Japan. Sixty-nine of the 86 horses in this study are horses from the same five equestrian clubs that we used in our previous study to examine T4 and iodine concentrations [ 9 ]. Thus, this study includes further analysis of the horses from the three equestrian clubs in Chiba (Chiba 1, 2 and 3; n=15, 12 and 5, respectively) and from one equestrian club each in Saitama (n=12) and Shizuoka (n=25) described in our previous report [ 9 ].…”

“…We previously reported that the mean serum iodine concentration in horses living in areas with higher environmental iodine contents [ 5 ] was completely higher compared with that in horses living in other areas [ 9 ]. Therefore, we suggested that estimating the serum iodine concentration in horses is helpful in environmental monitoring.…”