ANTIBODY-BINDING OF CIRCULATING ERGOT ALKALOIDS IN CATTLE GRAZING TALL FESCUE

Direct evidence linking alkaloids found in endophyte-infected tall fes cue forage with the livestock disorder known as fescue toxicosis is la cking. Physiologic effects of fescue toxicosis include reduced serum p rolactin concentration in cattle. A monoclonal antibody specific to th e lysergic moiety of ergot alkaloids was developed in mice after creat ing an immunogen by linking lysergol to human serum albumin. The antib ody was specific to the lysergic moiety and, therefore, it cross-react ed with ergot alkaloids, lysergic acid, and lysergol. The antibody did not cross-react with allkaloid derivatives that had bromated or hydro genated lysergic ring moieties. Fescue toxicosis conditions were elici ted in yearling Angus steers by permitting them to graze endophyte-inf ected tall fescue containing > 650 mu g/kg of ergo-valine for 60 days. Passive immunization of steers by infusion of the monoclonal antibody increased serum prolactin concentration by 7 ng/ml, beginning immedia tely after infusion. Control steers did not respond to treatment with bovine serum albumin. Active immunization of yearling Angus heifers wi th immunogens containing lysergol or ergonovine linked to human serum albumin resulted in an antibody response.