Abstract

Zearalenone is a naturally occurring mycotoxin from the Fusarium fungus which grows on pastures in New Zealand in autumn, and it has been found on farms in some years from Northland to Southland. The toxin may interfere with oestrogen-related functions in sheep during reproduction, reducing ovulation rates and fertility and thus lambing percentages, because its chemical structure is similar to that of reproductive steroids. Forty four per cent of over 6000 New Zealand pasture samples, collected in autumn and tested for zearalenone, were found to have high enough levels for ewe fertility to be either depressed (9% of samples), or `at risk` (35%). Control of zearalenone toxin production or of Fusarium growth on pasture on a large scale is currently not feasible. Attempts to mitigate its effects by immunisation have failed or even exacerbated the problem. Provision of alternative zearalenone-free feed crops is costly and generally uneconomic. Selection of sheep for genetic resistance would seem to be the most beneficial approach. Resistance to zearalenone is inherited in sheep (heritability estimate = 0.32 ± 0.10), and a test could be set up in ram-breeding flocks to select for resistance.

JF, Smith, and CA Morris

Proceedings of the New Zealand Society of Animal Production, Volume 66, Napier, 306-310, 2006