RESPONSES FROM COWS FED SILAGES CONTAINING DURSBAN RESIDUES

When corn was sprayed in the field with Dursban [O,O,-diethyl O (3,5,6-tricholoro-2-pyridyl) phosphorothioate] at rates of 0.28, 0.56, and 1.12 kg/hectare and ensiled one day later, losses of Dursban residue from time of application through harvesting of the treatments amounted to 56, 40, and 71%, respectively. The resulting silages fed during a seven-week period following 92 days from ensiling of the 0.28, 0.56, and 1.12 kg/hectare treatments averaged 2.71, 5.87, and 11.59 ppm Dursban (dry basis), respectively, which was near 70% of the Dursban ensiled. These residues did not cause a depression in silage intake or milk production. Milk and urine from the 12 cows ingesting residues at averages of 0.04 to 0.17 mg/kg body weight for 49 days were free of Dursban (<0.002 ppm) and its oxygen analog (<0.005 ppm). It was estimated that about 4 to 5% of the ingested Dursban was excreted in feces. Except for a small depression of blood cholinesterase activity (9% for cows fed silage averaging 11.59 ppm Dursban, dry basis), these cows did not show any ill effects that could be attributed to ingestion of Dursban residues. © 1969, American Dairy Science Association. All rights reserved.