Resources / Beef Cattle / Cow Calf / Herd Health Preventing Mycotoxins in Cattle: Minimize Mold Growth in Feed and Grain Each fall during harvest, reports of mold and mycotoxins may surface, and understanding the potential feeding issues is key to keeping animals healthy and performing. Prevention is the best method to control mold growth and possible toxin formation. The following pre-harvest and post-harvest practices along with suggested testing methods can help minimize mold growth and subsequent toxin production in storage and feed usage. Pre-harvest recommendations for limiting mycotoxins in feed and grain Clean inside and outside of grain bins and dryers. Prior to storage, check the condition of the bin for possible water leaks, and clean it properly by removing dust, dirt, leftover grain and other foreign material. Crop rotation in many regions or tillage can reduce the risk of Gibberella ear rot in corn and Fusarium head blight of wheat. These practices have little effect on other corn ear rots. Some corn hybrids are more resistant to ear rots than others, but overall, resistance to ear rots is not widely available. Control of second-generation European corn borers and other insect pests of corn ears can greatly reduce infection by Fusarium and Aspergillus. Few wheat varieties have high levels of resistance to Fusarium head blight (scab). Plant moderately resistant varieties when available. Planting several varieties that differ in maturity will reduce the risk of disease to the whole crop. As with any crop pest, early detection through scouting and early harvest can reduce serious losses and avoid crises. Decisions on handling moldy grain should be made before it is harvested. After harvest, spoilage can occur quickly if delays result from indecision. If extensive ear rot development is observed (10% or more of the ears with more than 10-20% mold), the field should be harvested as soon as moisture content reaches a level that can be harvested. Even if some drying costs are incurred, this will be less expensive than loss of crop value due to mycotoxins and resulting feeding problems. Post-harvest recommendations for limiting mycotoxins in feed and grain The crops should be allowed to mature in the field to the following moisture contents: shelled corn, 23-25%; ear corn, 20-25%; small grain, 12-17%; and soybeans, 11-15%. Harvesting equipment should be adjusted to minimize damage to seeds or kernels and allow for maximum cleaning. Cracked or broken seeds or kernels are more susceptible to mold invasion. Upon storage, dry the grain to 13-14%, if possible, within 48 hours. Long-term storage can be achieved at a uniform moisture of 18% for ear corn; 13% for sorghum, wheat and shelled corn; and 11% for soybeans. After drying, store under cool temperatures (below 40° F). If outdoor temperatures are still high at harvest, cool the grain in cycles with every 10-15-degree fall in average outdoor temperatures and run the fans during cool, dry nights. Pay attention to the air dew point temperature when cooling, as low dew points indicate good conditions for cooling. The time it takes to cool an entire bin depends on the airflow rate per bushel. A large drying fan (1 cfm/bu) will take 15 hours or so, while a smaller aeration fan (0.1 cfm/bu) will take at least 150 hours (close to a week). Every few weeks check the condition of the grain for temperature, wet spots and insects. How to test for harmful mycotoxins in cattle The presence of a fungus known to produce toxins is not proof that the grain contains injurious levels of toxin. Collecting a representative sample of grain for chemical analysis at a laboratory may be a good investment to determine mycotoxin presence. When sampling grain, particular attention should be given to the sampling procedure because sampling error will be the greatest source of variation in the analytical procedure. This variation is primarily due to the uneven distribution of the mycotoxin contaminated kernels within a lot of grain or feed. The ideal sampling procedure should assure the highest probability of detecting mycotoxins even when contamination is low. There are a few ways to sample grain, such as collecting an aggregate sample as the grain is moving in a stream in or out of bins, or by using a probe sampler. Because mold growth usually occurs in spots in the grain lot, the best sampling is done on recently blended lots of grain. With both sampling methods, the collected grain is pooled into a large aggregate sample that represents the lot · For shelled corn, it is recommended that the aggregate sample be about 10 pounds. The aggregate sample is coarsely ground at the lab. Most analytical procedures need only about 25 grams (0.9 ounces) of ground corn, so it is important that the aggregate sample be thoroughly mixed after grinding. A one- or two-pound sub-sample is then taken, and it is more finely ground. From this sub-sample, a final sample is taken for analysis. Contact your local KENT representative for support in analyzing and managing your mycotoxin risk. If the mycotoxin is present in the feed, it may be blended on farm to reduce the toxin to acceptable levels in small lots, and it may be a good idea to channel the feed to animals that are more tolerant. Important: Blending is not an approved practice by the FDA for interstate commerce. Learn the effects of harmful mycotoxins in cattle and other livestock Mycotoxins Reported in Detrimental Feed Concentrations (ppm = parts per million) This table summarizes the main mycotoxins that affect livestock production with species, upper limit safety and their effects noted. Zearalenone Species Concentration Duration Effect Swine Prepubertal gilts 1–5 ppm 3–7 days Hyperestrogenism, prolapse Open gilts, sexually mature Anestrus, pseudopregnancy Bred sows 15–30 ppm 1st trimester Early embryonic death, small litters Juvenile boars 10-50ppm Indefinite Reduced libido, small testicles Mature boars 200 ppm Indefinite No effect Cattle Virgin heifers 12 ppm Open Heifers Reduced conception Dairy cows 50 ppm Open Cows Reduced conception Poultry Broilers & Turkey poults 200 ppm Indefinite No effect Deoxynivalenol (vomitoxin, DON) Species Concentration Duration Effect Swine Feeder pigs 1–3 ppm 1–5 days Reduced feed intake Feeder pigs 5–10 ppm 1–5 days 50% reduction in feed intake, vomiting Feeder pigs 10–40 ppm 1–5 days Complete feed refusal, vomiting Sows 3–5 ppm Gestation or lactation Lower fetal weights or no effect Cattle Feeder cattle 10 ppm Indefinitely No effect Dairy cows 6 ppm 6 weeks No effect or slightly reduced feed intake Dairy cows 12 ppm 10 weeks No effect on milk production Poultry Broilers & Turkey poults 50 ppm Indefinitely No effect Fumonisins (FB1 and/or FB2) Species Concentration Duration Effect Horses All classes and ages >10 ppm 30 days Liver damage, leukoencephalomalacia, death Swine All classes and ages >25 ppm 30 days Reduced gain and feed efficiency, mild liver damage All classes and ages >50 ppm 10 days Reduced gain and feed efficiency, moderate liver damage All classes and ages >100 ppm 5 days Severe pulmonary edema, death Cattle & Sheep All classes >100 ppm 30 days Slightly reduced gain, mild liver damage All classes >200 ppm 14 days Reduced feed intake and gain, moderate liver damage Turkeys All classes >100 ppm 21 days Reduced feed intake and gain, mild liver damage FDA’s guidance level for total fumonisins in corn and corn by-products (not to exceed 20% of the diet) used for equine and rabbit feed products is 5 ppm (1 ppm in finished feed). Aflatoxins (ppb = parts per billion) Species Concentration Effect Swine All classes and ages 200 ppb Slow growth, reduced feed efficiency All classes and ages 400 ppb Liver damage and immune suppression Feeder Cattle All classes and ages 400 ppb Tissue residues All classes and ages 700 ppb Mild liver damage, reduced growth and feed efficiency All classes and ages 1,000 ppb Moderate liver damage and weight loss All classes and ages 2,000 ppb Severe liver damage, jaundice, death Dairy Cows Lactating cows 20 ppb Detectable aflatoxin in milk Lactating cows 1,500 ppb Decreased milk production Poultry Broiler chicks 210 ppb No effect Turkeys 250 ppb Reduced growth Broiler chicks 420 ppb Lose weight, moderate liver damage after 3 weeks Horses All classes and ages 400 ppb Liver damage and immune suppression Munkvold, G., Osweiler, G., Hartwig, N. 1997 Iowa State University Ext. PM-1698 FDA has set a maximum limit of 20 ppb for aflatoxins in commercial grains used in feed for immature animals, dairy animals, poultry, horses, turkeys, and for unknown use. *Information was derived from The Ohio State University (OSU) website that is a cooperative effort among numerous land-grant universities. Also, included in this OSU document are preventative practices pre-harvest and post-harvest, as well as steps and methods for testing. All trademarks are property of KENT Nutrition Group and its affiliates. ©2025 Kent Nutrition Group, Inc. All rights reserved.
