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Climate changes and the global mycotoxin threat

Guilherme Bromfman for Progressive Dairyman Published on 11 March 2016
Johanna Fink-Gremmels

Dairies around the world should be concerned about mycotoxins emerging on the farm as fungal threats continue to affect animal, plant and ecosystem health.

Global disease alerts persist, and several species face possible extinction or extirpation each year.

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Mycotoxins are fungal metabolites produced by molds under conditions of stress. One of the most neglected considerations, mycotoxins should be a major animal health and welfare concern in modern animal husbandry, according to one leading researcher and veterinarian.

“Under the conditions of modern agricultural practice, mycotoxin contamination of feed materials cannot entirely be avoided and is detected in almost all feed materials worldwide,” said Johanna Fink-Gremmels, Utrecht University in the Netherlands.

Fink-Gremmels says, “It is predicted that the prevalence of mycotoxins will increase due to changes in the climate.”

Fink-Gremmels spoke at several symposiums across the country this past fall, where she presented a snapshot of the global mycotoxin problem as well as the role mycotoxins play in the health and performance of dairy cows during her presentation, “Impacts of Mycotoxins on Dairy Cows.”

According to Fink-Gremmels, mycotoxins are currently the most prominent feed contaminants worldwide, attributing to a 25 percent decrease in genetic potential in dairy cows and an economic loss to the U.S. alone estimated at more than $1 billion annually.

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Natural toxins produced by diverse fungal species, mycotoxins are increasing in diversity through both pre- and post-harvest contamination.

Unfortunately, mycotoxins cannot be removed from feed materials. Pre-harvest contamination is highly variable. These toxins are weather- and climate-dependent on agriculture practices, crop protection and pest control. Plant-fungal interactions can also cause modified mycotoxins, exposing livestock to multiple mycotoxins.

“In a plant, mycotoxins are excreted by fungi into the plant tissue. Since mycotoxins are toxic for plant cells, plants will often conjugate mycotoxins as a protective mechanism, particularly Fusarium toxins as they are conjugated to sugar molecules (glucosinolation),” Fink-Gremmels said.

“Modified mycotoxins are not detected by common analytical procedures and can be liberated in the rumen, contributing to the total animal burden.”

On dairy farms around the world, Fink-Gremmels has seen one of the oldest mycotoxicosis issues re-emerging – ergot alkaloids. The toxin family of ergot alkaloids affects small cereals and grasses, and researchers are now seeing this group increasing in variability and scope, thus the reason many dairies may be observing the persistent problem of fescue foot in their herds.

Aflatoxins are another increasing global concern. These toxins often occur when there is reduced insect control and an increase of corn in rumen diets. Fink-Gremmels said climate change is considered one of the drivers of the increasing fungal prevalence, and consumer protection is the major concern. Aflatoxin B1 (AFB1) is most toxic and is classified as a human carcinogen.

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Detailed legislation prescribe maximum permissible levels of AFB1 in human foods and animal feeds, as AFB1 is converted in the liver of a cow to AFM1 and excreted with milk. Contaminated milk above the FDA regulatory levels must be discarded, causing an economic loss to producers.

Fusarium mycotoxins are the largest mycotoxin family with an increasing prevalence globally, primarily found in corn. Despite frequent exposure, no clear tolerance levels have been established; co-exposure to multiple toxins remains the major challenge for animal health. DON and ZEA are the most prevalent toxins in small grains, causing significant losses in pigs.

However, DON is largely converted in the rumen to DOM (de-epoxide, less toxic). Detoxification capacity depends on an intact rumen flora. ZEA may impair fertility (estrogenic effect) following long-term exposure. T-2 and HT-2 are also of increasing concern, as these toxins may exert direct effects on the rumen mucosa.

Fumonisins have proven stability in the rumen, and oral bioavailability is often very low.

Producers should be aware that Fusarium toxins in pasture grass can cause distinct antimicrobial activity and impairment of rumen microbiota. There is also considerable level of uncertainty concerning the tolerable intake following long-term exposure.

TMRs can often contain more than one fungal species, contributing to a complex mixture of mycotoxins and unresolved health issues in the herd. According to Fink-Gremmels, the greatest problem for dairy cows is multiple mycotoxin contamination in silage.

Dairy producers need to observe cow signals such as reduced feed intake, reproductive disorders, laminitis, mastitis, impaired liver function, poor response to vaccination programs and increased susceptibility to bacterial and viral diseases, which can all be attributed to ingesting mycotoxin-contaminated feed.

“The first target for mycotoxins is the rumen microflora. Most fungal metabolites have antimicrobial activity. Rumen acidosis, variable rumen overgrowth of E. coli and inflammation are also possible challenges associated with mycotoxin exposure,” Fink-Gremmels said.

“Secondary effects are laminitis, mastitis, production loss and bacterial interactions in the feed and in the animal. Calves are often the neglected species, which can mean a difficult life start and immunity challenges.”

Mycotoxins in ruminant diets have been an overlooked area for a long time. Ruminants are generally exposed to diverse mycotoxins because their diet contains concentrates as well as forages. Intervention strategies should improve the rumen flora, which is the cow’s natural defense, and reduce the bioavailability of mycotoxins.

“The rumen determines the health and productivity of the cow. When rumen bacteria are suffering, the liver does not function properly, initiating a cascade of events, instigating a generalized inflammatory response, increase in somatic cell count, reduction in digestibility and ultimately resulting in the loss of production,” Fink-Gremmels said. “Intervention strategies can improve the rumen flora and reduce the bioavailability of mycotoxins.”

Some common practices for dealing with a mycotoxin issue in feed include:

1. Eliminate the suspected source of the mycotoxin by monitoring crops during harvest.

2. Add mold-inhibition products (i.e., use of fungicides or mold inhibitors on the TMR or corn silage).

3. Use mycotoxin-sequestering agents in the feed. In many cases, the use of sequestering-agent products results in the clinical or subclinical symptoms disappearing and begins the progression of the affected animals or herd returning to normal.

When producers suspect mycotoxins are present, testing of feed samples prior to feedout through a laboratory is the best way to determine risk and needed course of action.  PD

PHOTO: Johanna Fink-Gremmels from Utrecht University in the Netherlands presents her findings on the role of climate changes and the challenges of rising global mycotoxin at an Alltech Mycotoxin Roadshow. Photo provided by Guilherme Bromfman.

Guilherme Bromfman is on the North America Mycotoxin Management Team with Alltech

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