Mycotoxins in Dairy Feed

Mycotoxins are toxic compounds made by certain molds. They can show up in corn silage, grains, hay and by-products, and they are often hard to see.

Key points

Mycotoxins come from molds and may be present in feed that looks fine
Weather, storage and handling all affect risk
Sample from many points and use a qualified lab
Interpret results with a nutritionist or veterinarian
Good packing, covers and clean-out reduce mold growth

What mycotoxins are

Molds grow on crops in the field and in storage. Some of them produce toxins that can affect animals eating the feed. A feed can contain mycotoxins even if it looks and smells fine, and moldy feed does not always contain them.

Different toxins have different effects, and cows are often exposed to more than one at a time.

Buy feed from suppliers who can describe their handling and storage, and ask for testing information when a load looks or smells off. Keep a sample of each load for a short time in case questions come up later. Ask your nutritionist whether any of your feeds carry a higher risk this year because of weather during the season.

How feed gets contaminated

Weather in the growing season, crop stress and insect damage can all raise the risk before harvest. After harvest, poor packing, slow feed-out, rain, leaks and warm, humid storage give mold the chance to grow.

Every ingredient in the ration can contribute, including purchased feeds and by-products.

Keep records of which forage or grain was fed to which group and when. If a problem appears, those records help you and your advisers trace it back and decide what to test. Keep feed-out steady so the face does not sit exposed and warm for long. Keep a close eye on corn silage and high-moisture grain in particular, since both can spoil quickly when air gets in.

Drought or wet stress in the field
Damaged or insect-injured grain
Poorly packed or uncovered silage
Slow feed-out in warm weather
Wet or heated bulk feed

What herds may show

Signs can be vague: reduced intake, lower milk, poor fertility, more digestive upsets, higher somatic cell counts or more illness than expected. These look like many other herd problems, which is why mycotoxins are hard to confirm.

Concern grows when several signs appear together and began after a change in feed. Keep records of when problems started and what feed was in use.

Check bunk and silo walls and floors during humid spells, since mold can spread from a small leaking spot. Repair roofs and covers promptly. When a lab report comes back, ask exactly which toxins were measured and which were not, since a test only looks for what it is asked to find. Share the history of weather and storage with your advisers, since it often points to the likely culprit.

Sampling and testing

Sampling matters because mycotoxins are unevenly spread in feed. Take samples from several places and depths, mix them and send them to a qualified laboratory. Ask the lab how to collect and ship samples and what tests suit your situation.

Interpret results with a nutritionist or veterinarian. Test results show a snapshot, and the level at which a toxin matters depends on the animal and the combination of toxins. Do not set your own limits from memory. Do not mix suspect feed into the whole ration without advice, because spreading a problem across every cow is harder to undo.

Prevention and management

Prevention begins in the field with good crop practices and timely harvest. In storage, pack silage well, cover it tightly, manage the face and keep feed dry. Clean out old feed from bunks, bins and mixers regularly.

If a feed is suspect, talk to your nutritionist before feeding it. Options may include dilution, using the feed in a less sensitive group or discarding it. Ask your veterinarian about any products sold to bind toxins, since claims vary.

Safety and disposal

Moldy feed can also be a respiratory hazard for people. Use dust protection when handling it and follow safety guidance from OSHA and extension specialists.

Dispose of badly spoiled feed according to your state and local rules, and keep it away from animals.

Common mistakes

Assuming clean-looking feed is safe, testing a single grab sample and feeding suspect feed to the most vulnerable cows are common. Another is waiting a long time before getting help.

If milk goes down and the herd looks off, bring in your nutritionist and veterinarian early.

When to get help: Contact your veterinarian and nutritionist if you suspect mycotoxins, and ask about proper sampling. If cows are treated for any illness, follow label and veterinarian-set milk and meat withdrawal times exactly.

Sources and further reading

Organization homepages are linked so you can search them for current guidance on this topic.

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