Tolerance of Farm Animals to Feed Containing 2,4-Dichlorophenoxyacetic Acid

Abstract

Sheep and cows graced pasturage treated with a liberal application of weed killer (2,4-dichlorophenoxyacetic acid and Carbowax mixture). There was no apparent reduction in its palatability. The 2,4-D consumed either on pasture grass eaten by sheep and cows or in the ration fed to a cow at the rate of 5.5 grams daily, produced no apparent harmful effects in the health and performance of the animals. Post-mortem examinations revealed no pathological conditions in cows grazing on pasture treated with 2,4-D nor was this material found to be present in the liver, kidney or fatty tissues of a cow fed 2,4-D. By means of a biological method of assay, the presence of 2,4-D was demonstrated in the blood serum of a cow fed 5.5-grams of this material daily for 106 days. Results of these tests indicate that the 2,4-D probably occurred as a water-soluble salt. The 2,4-D was not found to be secreted into the milk nor was it found in the blood serum of a calf fed milk from the cow that received it in her ration. It is concluded from these data that the amount of 2,4-D that might be consumed by cows or sheep from pasturage sprayed with this material to kill weeds would not be injurious. The present experiments are based on the use of purified 2,4-D together with Carbowax and, while they indicate that the acid is not toxic, the results are not applicable to proprietary formulations that might contain other ingredients.