Experimetally Induced Equine Bracken Poisoning by Thermostable Antithiamine Factor (SF Factor) Extracted from Dried Bracken

Abstract

In order to elucidate the significance of thermostable antithiamine factor (SF factor), as one of the inducing factors of equine bracken poisoning, 2 horses were given orally with fluid extracted from dried bracken with water and heated at 100°C for 30 minutes to inactivate aneurinase. The extracted fluid was adjusted daily with dried bracken, which was 8.1 g/kg of body weight in one horse and 1.13 g/kg in another. The former horse manifested typical symptoms of bracken poisoning, including stiffness, staggering, and inability to stand for 29 days. The latter showed only temporal stiffness during an experimental period of 83 days.
Administered with the fluid containing SF factor, both horses presented a marked decrease in blood thiamine concentration and daily excretion of thiamine in urine, and an increase in pyruvic and lactic acids in blood. It was concluded that bracken poisoning was caused by not only aneurinase but also SF factor, which had also an antithiamine action.