Fanweed toxicosis in cattle: case history, analytical method, suggested treatment, and fanweed detoxification.

Two hundred and twenty head of pregnant cows were fed virtually 100% fanweed (Thlaspi arvense) in November 1984. One hundred became distressed and colicy within 4 hr of feeding. Eight died over the next 5 days despite removal of the feed and symptomatic treatment. Necropsy revealed massive submucosal edema of the wall of the forestomachs, particularly the rumen. Four abortions occurred. The feed was analyzed and was found to liberate 250 mg/100g of AITC. Possible methods of treatment were devised in case the problem should recur. Fanweed contains sinigrin and the enzyme myrosin. When the plant is crushed and moistened, allylisothiocyanate (AITC) is formed along with glucose and potassium acid sulfate. Application of Le Chatelier's principle led to an investigation of the effect of pH on in vitro generation of AITC. Methods of destroying AITC were also examined, and detoxification studies were undertaken on fanweed.