Effects of organic phosphate systemic insecticides on bovine embryonic survival and development

Experiments were conducted to determine effects of 2 organic phosphate systemic insecticides on embryonic survival and possible teratogenesis in cattle. A total of 726 heifers at 3 locations were treated with either crufomate (4-tert-butyl-2-chlorophenyl methyl methylphos-phoramidate) or coumaphos (O,O-diethyl O-(3-chloro-4-methyl-2-oxo-2H-1-benzopyran-7-yl) phosphorothioate). The compounds were administered to pregnant bovine females at various stages of gestation by pouring along the dorsal midline. None of the treatments, including those at recommended one-time doses, one-time doses at double or triple the recommended dose levels, or doses at recommended one-time dose levels repeated each day for 10 days, gave evidence of increasing embryonic death rates or of teratogenic effects. In one experiment, the crufomate compound had apparent erratic effects on serum ace5ylcholinesterase activities, but no effects on electrocardiographic patterns, heart rate, or respiration rate. Rectal palpation for pregnancy determination during the 35- to 44-day stages of pregnancy is discussed as a possible, but unsubstantiated, cause of congenital malformation of the caudal portion of the intestinal tract in 1 calf born during these studies and in other calves previously observed.