Diagnosing mycotoxicosis a challenge

Last updated 07:39 06/01/2014
Dr Lucy Waldron.
Fairfax NZ
DIFFICULT DIAGNOSIS: Dr Lucy Waldron, a leading animal nutrition consultant and researcher, says one of the biggest challenges when dealing with mycotoxicosis in farm animals is simply making a diagnosis.

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Leading animal nutrition consultant and researcher Dr Lucy Waldron says one of the biggest challenges when dealing with mycotoxicosis in farm animals is simply making a diagnosis.

Dr Waldron, who has been involved with mycotoxin research in grazing animals since 2002, said there were many challenges facing practitioners seeking to make field diagnosis, including the non-specific nature of many of the symptoms, and that mycotoxins almost never present as single toxins.

Mycotoxins are substances naturally produced by moulds and fungi that are normally present as some form of defence for the organism.

Hundreds of these mycotoxins exist, and contamination of natural materials with multiple toxins, either from one or several fungi, is common.

New Zealand has the perfect climate - warm, wet and temperate - for moulds and fungi to thrive.

In dairy cows, mycotoxicosis can present as unspecified disease, resulting in high veterinary and testing costs as a diagnosis is sought in vain.

Depending on the type of mycotoxin affecting the animal, a number of illnesses or symptoms can occur from feed refusal to impaired metabolism, poor immunity, and reduced productive performance.

"Animals with mycotoxicosis present with multiple symptoms and are hard to diagnose, having major impact on welfare, performance, food safety and profits," Dr Waldron said.

"There are always multiple contaminations with different symptoms; they are incredibly difficult to pinpoint."

The health impacts from mycotoxicosis are diverse and have varying degrees of severity.

Maize, grain and corn silage can contain fusarium toxins, which can cause liver and immunity damage and suppression (leading to poor disease recovery, robustness and mastitis), hay and silage can contain penicillium, which can affect respiration, while other mycotoxins can cause reduced nutrient absorption and impaired metabolism (affecting milk production and quality), and affect endocrine and exocrine fertility (return to service delayed), among other health issues.

Dr Waldron also discussed the impact of mycotoxins on food safety. "For every 65 units of aflatoxin ingested by cows, one-three units are transferred to milk.

"This is a food safety issue. It is important for the consumer and the farmer to have guaranteed food safety."

However, to test foodstuffs and milk for mycotoxins present would be extremely time consuming and enormously expensive.

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Dr Waldron suggested that if New Zealand was to ever test for the presence of mycotoxins, it would be wise to follow the EU's example.

"The EU [European Union] has a strict maximum permitted level of mycotoxins.

"Dockside sampling tests for a number of representative toxins and whether they are heavily contaminated or not. If they are, they are blended with materials that are within the permitted range."

- The Timaru Herald

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