· Zearalenone, (pronounced zeer al en own), is a fungal toxin produced by the fungus Fusarium. It is also called F-2 toxin.
· Fusarium is the name given to a large group of fungi. They occur through out New Zealand.
· The fungi have been found in numerous feeds including pasture, maize, barley and other feedstuffs. The Fusarium associated with ewe infertility is a saprophytic fungus, this means it grows on dead material, that preferentially grows on dead litter at the base of the pasture.
· The maximum growth is during warm dry conditions, i.e late summer and the autumn. Spores are formed under warm dry conditions.
· High zearalenone levels occur under a wide range of weather conditions so high risk times are difficult to predict.
· Spore counting is of no value.
· The toxin produced is oestrogenic, and results in ewes that absorb the toxin having changes in their oestrus behaviour (heat) and a reduction in ovulation and fertilisation rates. The ewes have a shorter cycle length and an increased duration of heat.
· This results in a decreased lambing percentage via an increased number of barren ewes and fewer multiple births.
· Lambing percentage falls by about 5% for every mg of zearalenone ingested per day. This occurs after 10 to 15 days of grazing zearalenone toxic pasture. Exposure for a longer duration results in increased depression of lambing percentage.
· The oestrogenic effects also effect males, with reduced libido, testicular atrophy and reduced sperm production. The significance has not been proven in New Zealand.
· In cows enlarged mammary glands, and prolapse of the rectum and vagina are symptoms. This may have some relevance to prolapses in ewes.
· Suspect a problem if scanning or lambing percentages are inconsistent with mating weights after excluding other obvious problems.
· Pasture samples will indicate the presence of zearalenone. One ppm in a bulk grass sample appears to be a toxic level for ewes. Studies indicate 3mg/ewe/day is toxic.
· Urine testing for a zearalenone metabolite, zearalenol is the best indicator.
· Prediction of the severity can be made, as urine zearalenol increases with increased zearalenone intake.
· Urine from 12-15 ewes should be collected and bulked together. Importantly an equal quantity from each ewe is bulked together. 0.5 to 1 ml each is sufficient.
· Methods of collection of pasture, urine and sample handling is best discussed with the clinic.
· The effect is worst the greater the amount and length of exposure.
· No treatment or vaccination for zearalenone is available
· Resistance to facial eczema does not confer resistance to zearalenone.
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