Increased mycotoxin risk from drought-stressed maize

By Peter Reis, Ruminant Feed Specialist

This summer’s extremely dry weather, followed by rain will increase the risk of mycotoxin presence in already stressed harvested crops this year with particular risk to cereals and maize.

During my time at Harper Adams University, I was involved in research involving mycotoxins which sparked my interest in this subject.

Last year our mycotoxin testing in maize showed 86% of samples reported a moderate to a high level of challenge, despite being grown in relatively good conditions compared to this year when the plants were under much greater heat stress.

The Hy-Sil project – involving Mole Valley Farmers, Bristol Vet School, University of Nottingham and Duchy College – found 89% of maize samples and 71% of Total Mixed Ration (TMR) samples tested positive for mycotoxins.

Nearly half the maize samples, 42%, were high risk. Although a crop may look healthy there
could still be mycotoxins present. They are highly toxic substances which occur naturally from
a variety of moulds growing on forages and feeds.

Mycotoxins are mainly produced as a result of disease in the standing crop. As the mould grows on the crop mycotoxins are released as part of the normal metabolism of the fungi. The production of mycotoxins tends to increase in the time up to harvest, as the crop ripens.

The susceptibility to disease is increased when the plant is stressed by extreme heat followed by heavy or continual rain, with dead or dying leaves being hot spots.

As these toxins are not bacterial, they cannot be killed by any additives or acids. The only way to effectively deal with a mycotoxin challenge is by using a good-quality broad-spectrum mycotoxin deactivator.

Rumi-TOX™ contains the first additive to be authorised in the EU to specifically counteract mycotoxins, with a minimum toxin binding capability of 90%.

It works in the rumen to effectively bind, detoxify and protect against mycotoxins producing non-toxic metabolites.

These effects are the result of several factors including decreased feed intake or refusal, with many mycotoxins having an antimicrobial effect, microbial populations can be negatively altered to decrease feed digestibility ultimately leading to reduced fatty acid and microbial protein production which finally limits nutrient availability for milk synthesis.

It was previously believed ruminants were resistant to the mycotoxicosis challenge due to the ability of the rumen to degrade some types of mycotoxins.

However, the latest research has provided a greater understanding of the rumen’s ability. Some factors affecting the level of degradation include:
• Modern dairy cows have a high outflow rate from the rumen meaning microbes do not have adequate time to break down the toxins.
• Complex diets can provide a cocktail of mycotoxins which can act together to exert negative effects on the animal.
• Subacute ruminal acidosis in dairy cows causes reduced protozoal populations in the rumen, (these are one of the most important degrading agents in the rumen), meaning more mycotoxins
are able to pass into the intestine, be absorbed and have a negative impact on cow health and productivity.
• Some types of mycotoxins are not able to be detoxified by the rumen and always require external intervention.

Feed-like dried distillers grains (DDGS) provide valuable energy but pose a significant mycotoxin risk. The main mycotoxin in DDGS is deoxynivalenol, a trichothecene which needs greater intervention than binding, like the advanced detoxification strategy employed by Rumi-TOX.

Feeding Rumi-TOX this year will help you to maximise the potential of your ration and make the most of your silage.