Neotyphodium species are fungal endophytes best known for their protection of grass hosts and production of bioactive metabolites including ergot alkaloids. Perennial ryegrass-Neotyphodium sp. Lp1 symbiota that have altered ergot alkaloid profiles (resulting from knockouts in two different endophyte genes) were fed, along with controls, to rabbits to test the effects of ergot alkaloids on food preference and satiety. Interestingly, rabbits dramatically preferred plants that were endophyte-infected but free of ergot alkaloids over endophyte-free plants (P = 0.01). Accumulation of ergot alkaloids of the clavine class counteracted the added appeal of endophyte-infected plants. In satiety tests, consumption of ergovaline (the ultimate ergot pathway product in wild-type endophyte), but not of several other ergot alkaloids, during an initial meal had a negative effect on subsequent rabbit chow consumption (P < 0.05). The data indicate that clavines were sufficient to reduce the appeal of endophyte-infected grasses, whereas only ergovaline reduced appetite.