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Fungus Cause Of Ewe Infertility

Ruakura researchers have discovered evidence that a fungus is a major cause of barren ewes and low lambing percentages.

The Mycotoxic Diseases Group has found that infertility is strongly linked to pasture contamination by zearalenone, a mycotoxin produced by Fusarium fungi. The several species of fungus involved are found throughout New Zealand, and a survey has shown high levels of the toxin in many areas.

The survey results show that ewes in all sheep-raising areas of the North Island are at risk from zearalenone-induced infertility. MAF scientists hope to expand their sample area to build up an accurate picture of the problem.

"Affected flocks had histories of multiple disturbances in the reproductive process, including reduced cycle length, increased duration of oestrus, fewer ewes ovulating and decreased numbers of ovulations," said one researcher.

Attempts have been made to vaccinate ewes against the toxin, but apparently served only to reduce fertility further. Pasture and grazing management was a more appropriate response, according to the scientists.

Fusarium grows predominantly on dead matter at the base of the pasture, and the highest levels of toxin are found there. The researchers have found that contaminated pastures retained high levels of zearalenone throughout the season, and that they did not respond to standard facial eczema fungicides.

"It will obviously be important to minimise pasture dead matter content by careful grazing management," notes group leader Dr Neale Towers.