Zearalenone - Toxin reduces lambing percentages
If, in talking to most sheep farmers, you happen to mention the words “Fusarium” or “Zearalenone” you will probably be met with a blank look. Yet the toxin Zearalenone produced by the fungi Fusarium, probably has had a greater effect on lambing percentages than any parasite or disease factors, including facial eczema.
This fungi lurks in the litter of traditional rye grass dormant pasture in company with many other fungi, including those that cause facial eczema and grass staggers. It was first discovered in the Gisborne region about four decades ago by scientists investigating the causes of poor lambing percentages.
In the 1990’s Dr Neil Towers (Ruakura) spent many years investigating the effects of this toxin on reproductive performance. He found that normal cycling patterns were disrupted which resulted in fewer eggs being shed which in turn led to lower lambing percentages – up to 20%. He also found that the levels of the toxin varied greatly between paddocks.
In the veterinarian publication “The Sheep – Health, Disease and Production”, it states “ewes absorbing zearalenone have changes in oestrus behavior, and a reduction in ovulation and fertilization rates”.
Several months ago, I received a telephone call from a good friend, John Lane, who with his wife Chris, farms a beautiful 280 hectare property on the Tapora Peninsula in the Kaipara Harbour. He was mystified as to the causes of his poor lambing percentage, and in particular, the reasons why 90 two tooth ewes out of 400 did not lamb. John is a top farmer and stockman and more observant than most. His rams and ewes were in good condition, there was no FE effect and the ewes were vaccinated against the two causes of abortion. It should all have added up to a very good lambing. In addition, John found more late lambers than usual and fewer multiples across the whole flock.
Around the same time, I received a telephone call from Lance Paganini, PGG Wrightson wool consultant operating out of Whangarei. He advised that he had a number of clients who reported poor lambing percentages over the past two years. There was a similar pattern of fewer twins and more than expected dry and late lambing ewes, especially in the younger sheep. I suggested to both John and Lance that the cause of the problem was almost certainly the toxin Zearalenone.
I too have been seriously affected over the past two lambings. Three years ago, I had a great lambing with plenty of multiples, few dries and late lambers. In contrast, in spite of normal environmental conditions at the time of mating, the past two lambings have been very disappointing with many dry ewes and late lambers among the younger ewes and fewer multiples across the whole flock. In the older ewes – third lambers and above – the dry rate was only 1.6%. However, these ewes obviously shed fewer eggs, as multiples were far less than expected. The ewes were single mated in different paddocks. At lambing time it was noted that the twinning rate between sire mobs varied greatly. There was a four-fold difference between the best and worst mobs. This ties in with Ruakura’s finding that toxin levels varied between paddocks. It is my belief that when toxin levels are very high ewes cease cycling altogether.
So what can be done to mitigate the effects of this toxin? First, ram harnesses should be used to see if ewes – particularly young ewes – are cycling (in my experience, it appeared that the late lambing and dry ewes were not marked in the first two cycle periods). Secondly, if a farmer suspects that there is a problem, he could try grazing his ewes – particularly his two tooths – on alternate plant species prior to and during early mating. Plants like chicory, plantain, fescue and clover, along with crops could reduce zearalenone intake.
All fungi seem to thrive in the litter created by the traditional rye grass dormant pastures (John Lane this year is grazing his young ewes on kikuyu dormant pasture).
In my opinion, ewes do develop a degree of immunity after a couple of years of exposure, sufficient to allow them to conceive, but at a lower ovulation rate.
From a national perspective, I believe there needs to be a programme to assess the extent of the problem and what it is costing farmers and the nation. Such a programme should be extended over several years as there are indications that toxin levels vary considerably according to environmental conditions.
Other Facts about Zearalenone
Another fungi, acremonium, common in New Zealand is also thought to produce the toxin zearalenone.
Zearalenone also affects other animals such as pigs and cows. In cows it affects the mammary glands and can cause prolapse in the rectum and vagina.
This toxin is also found in maize and barley.
It would appear that the conditions that favour the production of toxins that cause FE and grass staggers are different from those conditions that encourage the fusarium fungi. Over the past two years, when flocks have had zearalenone challenges, there has been no FE or grass staggers.
In the past it was considered that zearalenone was just a North Island problem. However we have noted that Clutha Vets in the past have investigated this fungi and its toxin. But, no-one really knows the extent of the problem in New Zealand as, to my knowledge, there has been no research in recent years.
From a ram breeder’s perspective, the presence of the zearalenone toxin before and during mating can adversely affect the accuracy of SIL (Sheep Improvement Limited) indices, particularly in the number of lambs born (NLB) index.
Any recording system assumes that all animals have equal opportunity.
Where ewes are single mated in different paddocks, those ewes in areas of high toxin levels could well have singles rather than multiples, or worse, be dry altogether. This will result in lower SIL figures that do not reflect the true genetic value of a ewe or her progeny. Such unfortunate ewes could be unjustifiably culled. Constant exposure to the toxin could result in the national flock gaining some resistance to the toxin, but this would take decades.