How Mycotoxins in Feed Affect Dairy Cow Fertility
Mycotoxins reach cows through silage, corn, and hay and often show up first as fertility trouble. Conception rates drop, heats stay quiet, and days open stretch out before you notice other signs like lower milk or loose manure.
Which mycotoxins matter most for breeding
Zearalenone acts like extra estrogen. Cows cycle irregularly or develop cysts. Deoxynivalenol (DON) cuts feed intake and weakens the immune response needed for embryo survival. Aflatoxin mainly hits the liver but still lowers conception when levels stay high for weeks.
| Mycotoxin | Common feed source | Fertility sign you notice |
|---|---|---|
| Zearalenone | Corn silage, high-moisture corn | Silent heats, swollen vulva, cystic ovaries |
| DON | Barley, wheat, poor haylage | Low dry-matter intake, early embryo loss |
| Aflatoxin | Stored corn, cottonseed | Gradual drop in conception after 4-6 weeks |
On one 220-cow farm the conception rate fell from 42 % to 28 % over two months. Feed tests later showed 1.8 ppm zearalenone in the corn silage face. Once they pulled that silage and added a glucomannan binder, the rate climbed back within six weeks.
When to test and what to watch
Run a full mycotoxin panel any time you open a new bunker or notice three or more of these in the same string of cows:
- More than 15 % of cows past 60 days in milk with no recorded heat
- Breeding dates that keep getting pushed back by 10-14 days
- Visible vulvar swelling in open heifers or fresh cows
- Silage that smells musty or shows visible mold on the face
Send samples from the actual TMR, not just the bunker, because mixing changes the final concentration.
Steps that cut exposure right away
- Keep the silage face straight and remove at least 15 cm per day so new mold does not form overnight.
- Add a glucomannan or yeast-cell-wall binder at 0.5 % of dry-matter intake whenever test results exceed 0.5 ppm zearalenone or 1 ppm DON.
- Store ground corn at moisture below 14 % and check temperature weekly; hot spots above 30 °C almost always carry aflatoxin.
- Re-test the TMR two weeks after any change in binder or feed source so you know the levels actually dropped.
Most herds see the biggest fertility lift from the first two steps alone. Binder cost usually runs $0.08-0.12 per cow per day and pays for itself once conception improves by even two percentage points.
