When lactating cows consume aflatoxin, it not only can be toxic to the cow but also appears in the milk within 24 hours. Generally, the levels of aflatoxin appearing in milk are 1 to 2 percent of the aflatoxin content of the feed. Lactating cows consuming feed containing 20 ppb or less of aflatoxin will have less than 0.1 ppb of aflatoxin in the milk. Violation of the 0.5-ppb limit will result in condemnation of the milk and additional milk cannot be sold until it has been tested and found free from aflatoxin. Research data indicate aflatoxins will clear the system of lactating dairy cows within 48 to 96 hours after the contaminated feed is removed from the ration.
Calves are much more susceptible than adult animals to the effects of aflatoxins.
Calves are more susceptible than adults are, therefore young calves should not receive aflatoxin contaminated feeds nor should their dam, since aflatoxin can be passed in the milk. It is also not advisable to give suspect feeds to pregnant animals for reasons mentioned previously. Older non-pregnant animals can tolerate contaminated feeds much better Reduced growth and efficiency has been documented in cattle weighing less than 300 pounds receiving diets containing 150 to 200 ppb of aflatoxin in the total ration dry matter. Cattle weighing over 300 pounds have exhibited reduced growth and efficiency, as well as liver damage at aflatoxin concentrations greater than 220 ppb in the total ration dry matter. In general, potentially harmful effects may be witnessed in all classes of livestock at aflatoxin levels of 20 to 130 ppb in the total ration dry matter.