Development of a feed-intake model for evaluation of toxins associated with endophyte-infected fescue

Abstract

Feed intake of rats may serve as a sensitive respondent to toxins found in endophyte-infected fescue. Unfortunately, there have been few controlled studies of feed intake to create a reliable model. In the present study, rats were fed diets containing different amounts of endophyte-infected fescue (E+) and ergovaline (EV; a primary toxin associated with fescue toxicosis) to develop a dose-response curve for feed intake. Dose-dependent reduction in feed intake was observed, with a decrease even at the lowest concentration of EV. Involvement of ergotamine (i.e. another toxin in E+) in fescue toxicosis-induced reduction in intake was evaluated by adding it to diets. In contrast to EV treatment, there was only a small reduction in feed intake with ergotamine, followed by rapid recovery to pretreatment levels. A more effective paradigm for evaluating the effect of different toxins on feed intake and potential treatments may be a restricted feed regimen. Rats placed on a 2-h restricted-feed program of ground commercial chow followed by E+ diet show a decrease in both feed intake and growth. Future studies will refine this routine to identify specific effects of toxins found in endophyte-infected fescue on feed intake. Keywords: rat, fescue toxicosis, feed intake