It was hypothesized that a tannin-rich legume like sainfoin reduces the negative postingestive effects of ergot alkaloids in tall fescue. Thirty-two 3-mo-old lambs were individually penned and randomly assigned to a 2 × 2 factorial experimental design with 2 legume species (sainfoin [SF; tannins] or cicer milkvetch [CIC; no tannins]) and a ration (seed:beet pulp:alfalfa, 50:30:20) containing 2 types of tall fescue seed (endophyte-infected [E+;1,745 ppb ergovaline] or endophyte-free [E–]). For a 10-d baseline period, all groups were fed their respective supplemental legumes (17 to 25 g DM/kg BW) and ad libitum amounts of E–. In an ensuing 10-d testing period, the protocol was the same but half of the lambs received E+ instead of E-. Daily feed intake and rectal temperatures were measured for both periods and jugular blood was extracted at the beginning and end of the testing period. Subsequently, all lambs had choices between their respective legume (SF; CIC) and seed-containing rations (E+; E–). Response variables were analyzed using a mixed effects model, which included legume, ration and day as fixed effects and lamb as a random factor. All groups consumed similar amounts of E– during baseline (P > 0.10). However, lambs ate more E– than E+ during testing (P < 0.05) and lambs offered SF ate more E+ than lambs offered CIC (P < 0.05). Groups fed E– during baseline and testing periods had similar rectal temperatures (P > 0.10). However, lambs fed E+ had lower rectal temperatures when supplemented with SF than with CIC (P < 0.05). Lambs fed E+ had a greater concentration of hemoglobin and number of red blood cells than lambs fed E– (P < 0.05). Plasmatic concentrations of cortisol and prolactin did not differ between treatments (P > 0.10). All lambs preferred their respective rations over their respective legumes and they preferred E– over E+ (P < 0.05). In summary, SF increased intake of E+ and reduced rectal temperatures relative to CIC supplementation. However, SF did not lead to changes in preference for E+ or improvements in other physiological parameters assessed.