A feed-restriction model to identify factors responsible for fescue toxicosis-induced reduction in food intake [abstract]

Abstract

Fescue toxicosis results from intake of ergopeptine alkaloids derived from a fungus (Neotyphodium coenophialum ) in tall fescue, and produces reduced productivity. Contributors to this reduction are decreased feed intake and growth. There have been few attempts to characterize these changes. A study was conducted to develop a model for this component using rats in a feed restriction experiment described previously by others. Each animal was trained over a minimum 11 d period to eat their entire daily ration from 1300-1500. This allows one to evaluate the effect of potential treatments more precisely by using a 2 hours rather than 24. Group I animals were first fed in this order an endophyte-free seed (E-) diet (ad libitum ), a restricted E- diet, a restricted endophyte-infected seed (E+) diet, and lastly an E- diet (ad libitum ). There was no decrease in feed intake (α= 0.05) from restricted E- to restricted E+ diets, but reduced growth while on E+ diet. Return to E- diet restored growth. A different routine was used with Group II. Rats were first fed ground commercial diet (ad libitum ), followed by restricted ground diet, restricted E- diet, and lastly restricted E+ diet. Initial exposure to restricted diet decreased feed intake and growth (α = 0.05), followed by partial recovery or adaptation over following 4 days. Shift to restricted E- produced no change in feed intake and a greater return of growth. Restricted E+ diet intake reduced feed intake and growth within 24 hours (α = 0.05). This reduction was stable over the entire 2 week period. These responses agree with previous studies using long-term ad libitum E+ treatment. This new model can now be used to identify mechanisms for fescue toxicosis-induced reduction in feed intake and growth, and develop potential treatments.