Is there an absolutely safe level? The answer is probably no. For beef cows, including pregnant cows, a maximum of 100 ppb in the total diet appears to be a practical answer. Some would argue that any detectable level of aflatoxin will cause some harm.
Beef Cows
100 ppb maximum in total diet. Feed a ration balanced to meet protein, fiber, selenium, vitamin A, vitamin E, copper, zinc and other required nutrients.*
Six (6) pounds of corn containing up to 300 ppb each day for a pregnant cow eating 18 lbs of dry matter per day will provide 100 ppb or less in her total diet.
Eight (8) pounds of corn containing up to 300 ppb each day for a cow nursing a calf eating 24 lbs of dry matter per day will provide 100 ppb or less in her total diet.
Another method for lowering the level of aflatoxin is to blend the contaminated corn with clean corn or other feed ingredients to dilute the level that is in the total ration or grain mix. For example:
500 lb corn containing 300 ppb
500 lb corn containing 0 ppb
300 lb cottonseed meal
300 lb soybean hulls
100 lb molasses
This grain mix would contain only 75 ppb aflatoxins since the contaminated corn only represents 25 percent of the total ration. (From Aflatoxins in Feeds, Dr. Charles Hutchison, Dairy Specialist)
Replacement Heifers and Bulls
I would suggest that weaned and yearling age heifers and bulls be fed only 20 ppb or less aflatoxin in their diet. Certainly do not exceed the 100 ppb level suggested for cows. They are still growing and they represent the future genetics in your herd.
Stocker calves weighing 500 lbs or more
Do not exceed three hundred ppb in the total ration. Feed required amount of protein and include supplement package that will insure sufficient selenium, vitamin A, vitamin E, copper, and zinc in the diet.*
* Adequate protein, copper, zinc, vitamin A, vitamin E in the diet may offer some protection against adverse effects of aflatoxins.
Inorganic Adsorbent Materials
Research studies have demonstrated that hydrated sodium calcium aluminosilicate (HSCAS) reduce the absorption of aflatoxins from the digestive tract of chickens, lambs, swine, and dairy cattle. The product trade named Novasil is approved for use in poultry feeds as an anti-bridging agent to improve feed flow. Sodium bentonite also reduces aflatoxin absorption from the digestive system.
Use of the materials in the in the feed industry is limited to approved uses.