Wheat straw can be a welcome addition to your ration to meet effective fiber needs, but experts at Pioneer Hi-Bred International caution that you may see cow-health problems if you feed a lot of the moldy kind.

Visible molds that caused rust or other plant diseases this summer aren’t considered dangerous to cows, but secondary plant invaders like Fusarium or other mold species may potentially produce harmful toxins. If cows are at the peak of health, they probably won’t be bothered if rations include straw afflicted by these diseases. However, most herds walk the fine line of subclinical acidosis. Combined with other stressors, cows in these herds may show signs like rumen atony or diarrhea when fed moldy straw.

If moldy straw is your only option, get a mold count and identification so you know which microbes you’re dealing with. If the sample reveals toxin-causing mold species, and levels are above 100,000 colony-forming units per gram of forage, use the straw for bedding. If species are not deemed dangerous, experts recommend you consider using mold inhibitors and mycotoxin adsorbents in your TMR.