The effects of endophyte content on the nutritive value of drunken horse grass (Achnatherum inebrians) fed to sheep in Xinjiang province, China
2009
Norton, B.W. | Li, X.S. | Fletcher, I.
Drunken horse grass (DHG) (Achnatherum inebrians) is a weed of the grazing lands of China, and contains an endophytic fungi (Neotyphodium spp.) producing the neurotoxin ergonovine. The following experiments investigate the effects of endophyte and ergonovine content on the nutritive value and on the symptoms of toxicity of DHG hay fed to sheep in Xinjiang province, PRC. Endophyte infection in DHG was controlled by spraying with Banner Turf during early growth (Low Endophyte), and infected DHG hays (High Endophyte) were prepared from nearby untreated swards. These hays were offered ad libitum to 3 groups of 4 sheep held in metabolism cages indoors over a 4-week period. In the first year (1996), a legume per grass (LG) hay was used as control and 200 g maize given to each sheep daily. In the second year (1996), a local grass (Elymus siricibus) was the control, and no maize was fed. Sheep given the LG hay consumed more DM (861 g per d) than did those given the treated (305 g per d) and untreated (264 g per d) DHG hays. Treated hay contained only 75 g per kg DM ergonovine compared with 200 g per kg DM ergonovine in untreated hay, and had higher in vivo digestibilities (61.3 per cent) than untreated hays (54.8 per cent). All sheep consuming DHG lost weight, and in the second experiment, without maize supplements, sheep were taken off treatments after 3 weeks as a consequence of excessive weight loss. There was a significant positive correlation between endophyte infection and ergonovine content of DHG hay, and significant negative correlation between DHG hay intake and its ergonovine concentration. An oral dose of 60 g ergonovine (2.3 g per kg live-weight) was sufficient to induce severe symptoms of toxicity which abated 11 hours after dosing. It was concluded that even low concentrations of ergonovine in DHG hay depress hay intake and the potential productivity of sheep consuming DHG hay
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