Fescue Toxicosis Update/Bovine Hysteria from Ammoniated Forages Update

Abstract

Fescue toxicity in cattle includes three distinct entities: fescue foot, fat necrosis and summer syndrome. Summer syndrome has a considerably greater economic impact than either of the other disorders. Summer syndrome denotes poor performance by cattle grazing tall fescue, especially notable during hot, humid weather. Signs include reduced feed consumption, decreased rate of gain and / or milk production, rough hair coat, increased respiratory rate, increased body temperature and general unthriftiness. Only summer syndrome has been positively associated with infection of tall fescue by the fungal endophyte, Acremonium coenophialum.
Rare episodes of "crazy cattle" or "bovine bonkers" were reported from all over. Sometimes the syndrome appeared in cattle eating ammoniated feeds and in other instances it appeared in the calves nursing cows which were being fed ammoniated feeds. After several cases were investigated and compared, it was determined that the syndrome was related to what had occurred thirty years before when ammoniated molasses was fed to cattle. Ammoniated feedstuffs reported to have caused cattle bonkers include: forage sorghums, sudan hay, wheat hay, wheat straw, barley hay, oat hay, fescue hay , bromegrass hay , bermudagrass hay, orchardgrass hay, alfalfa hay and rice straw.