Correlation of endophyte toxins (ergovaline and lolitrem B) with clinical disease: Fescue foot and perennial ryegrass staggers

Fescue fool, summer syndrome, reproductive problems, and ryegrass staggers are all diseases of livestock related to endophyte toxins in pasture grasse s. Range finding experiments and case studies of fescue foot relative to er govaline toxin found in endophyte infected tall fescue and lolitrem B prese nt in endophyte infected perennial ryegrass were conducted. Within 42 dof i nitiating a feeding trial with chopped tall fescue straw containing 825 ppb ergovaline and at environmental temperatures of 15.9 C clinical signs of f escue foot were seen in cattle. Sheep on tall fescue pastures in November c onsuming feed with 540 ppb ergovaline and at environmental temperatures of 7.8 C developed fescue foot in 21 d while sheep on the adjacent field in th e previous 2 mo with environmental temperatures of 16.6 C and 12.8 C and 45 8 ppb ergovaline in the pasture grasses did not. In a field outbreak of res cue foot affecting 42/425 feeder lambs in November, the ergovaline of sampl e pasture grasses had a mean concentration of 813 ppb. Perennial ryegrass s taggers was seen in 42/237 feeder lambs when mean lolitrem B in the sampled grass was 2135 ppb. Overgrazing both tall fescue and ryegrass fields incre ased probability of clinical disease since the highest levels of toxin were found in the crowns and basal leaf sheaths of tall fescue and perennial ry egrass respectively. Based on these findings, ergovaline dietary levels of 400 to 750 ppb to cattle and 500 to 800 ppb to sheep and lolitrem B levels of 1800 to 2000 ppb in feed for both species are approximated threshold val ues for disease. Cold environmental temperatures are equally important to t oxin concentrations in precipitating fescue foot disease.