Investigations into perennial ryegrass staggers, a neurotoxic disease affecting sheep, cattle, horses and deer in New Zealand, recently incriminated a fungus growing as a endophyte in perennial ryegrass in the occurrence of this disease. This Lolium endophyte (an Acremonium sp.) is most prevalent in the lower parts of infected ryegrass plants (leaf sheath) but invades the inflorescence and seed. Newly-emerging ryegrass seedlings are so infected. The close association of the endophyte with the present of lolitrems, potent neurotoxic tremorgens previously isolated from staggers-producing pasture samples, further incriminated the endophyte in the occurrence of ryegrass staggers. Subsequent lamb grazing trials on plots sown with lines of either high- or low-endophyte ryegrass seed confirmed that adequate intakes of short- grazed ryegrass material readily produced ryegrass staggers in all lambs grazing the endophyte-infected plots but there was little or no disease on low-endophyte plots identically grazed. The trials also revealed that the spring-sown high-endophyte ryegrass plots had considerable drought resistance and persistence when compared with low-endophyte plots. The infected swards were found to be highly resistant to Argentine stem weevil attack and a significant insect- feeding deterrent factor has since been detected in endophyte-infected ryegrass. A subsequent sheep grazing trial was indicated that plots sown in autumn with fungicide-treated seed to control endophyte and then conservatively grazed in the first year subsequently gave good production and also provided excellent protection from ryegrass staggers.
Proceedings of the New Zealand Society of Animal Production, Volume 44, , 173-176, 1984
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