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 with the University of Guelph, Ontario, Canada. But reduced- and no-till cropping systems leave more crop residue at the surface of soils, allowing mold to grow between cropping seasons. Global climate change, with higher and more intense rains, then causes more mold growth. Weather stress also makes crops more vulnerable to fungal attack, which then increases the chances of mold growth on feed crops.
Not all molds produce toxins and the complex nature of molds and the toxins they produce all make detecting “safe” or “unsafe” levels difficult to decipher. 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. Instead, lower levels can have subtle effects on immunity which is sometimes blamed on vaccine failure during disease challenge. More mastitis and higher cell counts can occur as well. Plus, recent studies suggest molds can inhibit nitrogen utilization. In addition, if cattle are over-crowded or heat stressed, they are more susceptible to a Fusarium challenge.
“The only complete solution to the problems arising from mycotoxins is to avoid feeding mycotoxin-contaminated feedstuffs,” says Smith. 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 absorbents attract and bind the mycotoxin molecules as they pass through the intestinal tract, which prevents the toxins from being absorbed into the blood stream. “If you have highly fermentable feeds and it tests positive for mycotoxin, an absorbent is probably recommended,” says Smith.
Smith spoke at World Dairy Expo’s Educational Seminar Saturday. His presentation was sponsored by Alltech.