Mycotoxins (poisons created by certain molds) have always been a problem; however, with modern agriculture feeding practices and feed storage, they are more prevalent today. Larry Roth, vice president of nutrition at Agrarian Solutions, works with nutritionists, veterinarians and cattle producers to protect livestock from mycotoxins.

“Mycotoxins are produced by molds as part of their own survival mechanism — in what we call competitive exclusion,” he explains.

Molds readily start growing on plants that can’t fend them off. Anything that stresses and weakens a plant can tip the balance, making it more susceptible to things like mold, he says. Then, if the mold gets stressed by some of those same conditions, it produces mycotoxins to prevent other opportunistic organisms from establishing.

Many modern agronomic practices favor molds, Roth says. For example, crops today have a greater canopy density than is usually found in nature, which holds more moisture. This canopy density also blocks sunlight, the best disinfectant, so these molds can take off and grow.

“It’s also good farming practice to leave crop residue on the soil surface, using minimum till and no-till to increase organic matter in the soil,” he says. “When new green leaves emerge, coming up through that old residue, they become infected with molds, and if the molds get stressed, they create toxins.”

If we don’t pack silage properly or quickly cover it with oxygen-limiting plastic, the results are weathering, poor fermentation and an increase in molds and mycotoxins. Byproducts like distillers’ grains and corn gluten feeds concentrate and raise the level of mycotoxins compared to what was in the base feed, Roth notes. We also store feed, and sometimes storage conditions lead to mold formation due to poor harvest conditions or weather damage during storage.

“Today, our animals are exposed to higher levels of mycotoxins than they were in the past.” — Larry Roth

“Two hundred years ago, a brood cow was eating dry grass. She wasn’t fed corn silage or distillers’ grains. Today, our animals are exposed to higher levels of mycotoxins than they were in the past,” he explains. A pregnant cow in her last trimester might be fed silage or distillers’ grains because her nutrient requirements are greater as the fetus is growing faster.

“Thus, we are putting more mycotoxins into that cow, which lowers her immune defenses. Her immune system is her military — to defend her against invading agents. If the immune system is hammered by mycotoxins, this is a nutrient drain,” Roth says. “The cow only has a certain number of nutrient resources to allocate. Now some of the nutrients she was hoping to put into that fast-growing fetus and colostrum quantity and quality are diverted into defending herself. Her first priority is to survive.”

Now imagine that on top of that nutrient drain, she goes through a bad winter. The cold and wet conditions add more stress. If all these factors come together, the calf does not receive adequate antibodies from colostrum. Once she calves, she must produce milk and get ready to breed again. Unfortunately, some of her nutrients are being allocated to fight mycotoxins, and her performance will be impaired.

Mycotoxins can reduce the ability of beef cattle to reach their genetic potential; they steal money from the producer and nutrients from the animal.

“Mycotoxins are absorbed by the cow and can be stored in her fat. When she produces milk after calving, she starts to metabolize body fat. The mycotoxins stored there are now free to float through the body,” Roth explains. “The liver is the body’s biochemical factory and filter. Everything must go through the liver, so it is working hard to detoxify these mycotoxins. It is normally making glucose and other nutrients the cow needs, but is now impaired in that capacity because it is going through all the necessary detoxifying of mycotoxins.”

Mycotoxins reduce the nutrients available for productive purposes — whether it’s the calf inside the pregnant cow, colostrum for the calf at birth or producing milk for the calf at side. They reduce nutrients available for a young bull to successfully breed, and reduce the reproductive success of the heifer, says Roth. Thus, it is important to try to limit the level of mycotoxins encountered by our cattle.

Editor’s note: Heather Smith Thomas is a freelance writer and cattlewoman from Salmon, Idaho. [Lead photo courtesy of Getty.]