Mycotoxins are an increasing threat to herd health
Global climate change and reduced-tillage systems may be leading to increased levels of mold and mycotoxins in dairy cattle rations.
Molds have always been present in soils, says Trevor Smith, an animal scientist at the University of Guelph, Ontario. But reduced- and no-till cropping systems leave more crop residue at the surface of soils, allowing mold to overwinter. Global climate change, with higher and more intense rains, causes more mold growth. Weather stress also makes crops more vulnerable to fungal
attack, which increases the chances of mold growth on feed crops.
Not all molds produce toxins. In addition, the complex nature of molds and the toxins they produce makes detecting “safe” and “unsafe” levels difficult. At the very least, mold infestation often reduces the feed value of infected crops, usually lowering energy content.
If toxin levels are high—Fusarium at 200 ppm, for example—they can affect milk production and even cause liver damage. Levels seldom reach these heights. But lower levels can have subtle effects on immunity that are sometimes blamed on vaccine failure.
More mastitis and higher cell counts can occur as well. Recent studies suggest that molds can inhibit nitrogen utilization. And if cattle are overcrowded or heat-stressed, they are more susceptible to Fusarium.
“The only complete solution to the problems arising from mycotoxins is to avoid feeding mycotoxin-contaminated feedstuffs,” Smith says. But it is difficult to know when and if mycotoxins are present and at what levels.
If you suspect they are present, a more practical strategy is to feed mycotoxin absorbents. These attract and bind the mycotoxin molecules as they pass through the intestinal tract, which prevents the toxins from being absorbed into the bloodstream.
“If you have highly fermentable feeds and they test positive for mycotoxin, an absorbent is probably recommended,” Smith says.