Are your beef replacements developing their mammary glands too early? Are your cattle gestation lengths shorter than average? Have you seen any cases of intestinal hemorrhagic syndrome on your dairy farm? According to Gustavo Schuenemann, mycotoxins may be contributing to these health issues in your livestock. Schuenemann is a dairy cattle Extension specialist and veterinarian at Ohio State.
“Mycotoxins are toxic chemical compounds synthesized by microscopic fungus, mainly molds,” Schuenemann explained. “Some of these fungi produce a lot of chemical compounds. Some are beneficial to livestock, but a number of them have a toxic effect for livestock, whether it is beef, dairy or small ruminant.”
Currently, there are about 400 identified mycotoxins. The most common are aflatoxin, trichothecenes (for example, DON), fumonisins, zearalenone, ochratoxins and ergot alkaloids.
Schuenemann stressed that most mycotoxins are produced in the field rather than during storage. Research tends to focus on mycotoxin production in forage and grain crops, but grain byproducts – which come recycled from the food industry into cattle production – are an often overlooked source of mycotoxins on the farm.
Schuenemann reflected on the challenges of a 2022 growing season with limited rainfall, stressed plants and significant pest pressure in corn fields. These stress challenges, he said, triggered the production of mycotoxins in the field. Changes in temperature, humidity and substrate, in addition to pH and oxygen exposure, are all major factors that will cause molds to produce mycotoxins.
Recent studies have shown that 57% – 87% of total mixed rations (TMR) had two or more mycotoxins present. On average, TMR was contaminated with five mycotoxins. “Very likely cows are dealing with two, three, four or five mycotoxins, and these are the ones that we already know and we measure,” he said.
The negative health implications of mycotoxins are wide-ranging – reduction of rumen function, reduction of dry matter intake consumption and increased inflammation and lowered immunity. Milk production and reproduction can also be negatively impacted.
Specific health indicators of mycotoxins may include unusual drops in milk yield, unusual spikes in somatic cell count, an increase in aborted calves and displaced abomasa, diarrhea, intestinal hemorrhagic syndrome and mammary development in heifers.
Some of Schuenemann’s recent studies focus on gestation length and its connection to mycotoxin contamination in TMR. “I am using gestation length as a biological marker on farms to assess inflammation because I know when inflammation is triggered that also increases cortisol in blood, and cortisol is the driver to trigger labor,” he said. “So the cow goes into earlier labor because of the chronic exposure to some of these stressors.”
Producers should also assess their feed and facilities to help determine whether mycotoxins are responsible for the livestock health problems. Questions producers should consider include “Does the corn silage or other stored feeds have visible dark greenish spots or molds? Do the corn plants have signs of preharvest stress? Was the corn silage harvested too early?”
In addition to checking feed and infrastructure for visible molds, producers should do an honest assessment of cow comfort such as feed bunk space per cow, bedding space and access to water.
If the herd health and feed and facilities assessments point to mycotoxin contamination, the next step is to test the feed for mycotoxins. “Start with the TMR, and then go to specific ingredients if the farm has the ability to change some of the inclusion rates of these ingredients,” Schuenemann said.
He said to be aware of sampling variation in TMR and recommended pulling a sample right after unloading the mixing wagon. He also stressed using protective equipment in case mycotoxins are present. Liquid chromatography-mass spectrometry (LC-MS) is the gold standard for mycotoxin testing, according to Schuenemann. In his opinion, LC-MS testing is better than rapid testing, which provides limited information.
Medium to high levels of mycotoxins (as proven by testing) should trigger a change in management. Researchers still don’t understand the interactions between mycotoxins but conjecture that the presence of more than one may have an additive or even a multiplier effect. Because of this possibility, the control of mycotoxins is critical.
Binders (also known as adsorbents), fed as feed additives, are the most common tool to help livestock cope with mycotoxin-related health issues. These substances bind to mycotoxins and prevent them from being absorbed through the digestive system and into the blood circulation. Binders work best in a low pH environment.
The optimum binder is a combination of inorganics, organics and deactivators. Inorganics include mineral clay, aluminosilicates, bentonites and zeolites. Organics include yeasts, yeast cell walls, glucomans and algae. Deactivators include enzymes and microorganisms. This three-prong approach is necessary because each type of binder has different absorption capacities.
“It takes a broad spectrum because we are dealing with more than one mycotoxin,” Schuenemann said.
If not corrected properly with ration formulation, binders can reduce amino acids and mineral levels, specifically manganese, copper and selenium.
While binders may provide short-term control of mycotoxins, in the long-term producers should consider their selection index for health traits. “This is a more holistic approach. It appears that cows can tolerate more if in our selection index, we do provide more emphasis on health without neglecting milk yield and components,” Schuenemann said. “It appears that cows with strong immune systems are able to deal a little bit better with some of these pro-inflammatory chemicals.”
Another consideration is chopping height. Since mycotoxins are primarily soil borne, the closer equipment is to the soil, the more likely mycotoxins will be present in the forage or grain crop. Producers should also check for mycotoxins when buying any forage and feed ingredients and should discuss this with their veterinarian and nutritionist.
Finally, Schuenemann said that poor herd performance is not always associated with mycotoxins. Mycotoxin mitigation strategies, such as binders, will not solve issues related to poor cow comfort and/or inconsistent management. But an ounce of prevention is worth a pound of cure.
by Sonja Heyck-Merlin