The Effects of Coumaphos on Poultry and Its Residues in Tissue and Eggs12

In 1961, coumaphos (Co-Ral®) 50% oral drench powder in capsules at dosages of from 0.5 to 25 mg/kg was fed to laying white leghorn hens for 7 or 10 days. Dosages over 5 mg/kg caused considerable loss of weight and reduction in egg laying. At the 25 mg/kg level, all birds died. Analyses of tissues from treated birds showed no residues in excess of 1 ppm (the established tolerance). However, residues up to 0.09 ppm were recovered from egg yolks. In 1962, colony houses, 10×12 ft, containing laying white leghorn hens were treated as follows: 2 houses received a 5% dust at the rate of 2 oz/30 ft2 of floor space; 2 houses were fogged, using a Halaby fogger, with a suspension of coumaphos 25% wettable powder at essentially the same dosage used in dusted houses. Less than 0.15 ppm coumaphos were found in liver and fat of the exposed birds. The dust application resulted in no detectable residues of coumaphos in egg yolks. In one instance, a marginal residue of 0.03 was found in eggs from birds exposed to fogging.