Cattle-Hypoderma Lineatum Animal Systemic Insecticide Test, 1983

Government-owned Herefore, Angus, and Hereford-Angus-cross calves and yearlings on pasture at Camp Stanley and Camp Bullis, Vexar Co., Tex., naturally infested with the common cattle grub, Hypoderma lineatum (Villers), are treated with new insecticides that were determined to be systemically active in the mouse-Cuterebra animal systemic insecticide test (Drummond, R. 0., 1983, Insectic. Acaric. Tests 8: 256). Animals are weighed and given insecticides in initial tests either orally by capsule (usually technical grade insecticide) or dermally by whole-body spray of 4 liters/animal at > 150 lb/in2 usually formulated as an EC in xylene (65 parts), Triton X-100 (10 parts), and AI (25 parts) . In other tests, insecticides are administered dermally to cattle by pouron of a specific volume of insecticide (usually water-diluted EC as above or solution in oil) per body weight or intramuscularly or subcutaneously by injection of a specific weight of insecticide per body weight. Normally cattle are treated with new insecticides initially at the highest nonlethal dosages as determined by cooperating veterinary toxicologists; maximum dosages of initial tests are 100 mg/kg orally and 1% spray. If initial dosages are effective, cattle are given lower dosages in order to determine the minimum effective dosage. Other cattle are treated with titrated dosages of labeled systemics in order to determine systemic activity of dosages less than label-listed dosages. After treatment in May or June, the backs of treated cattle (usually 3 to 6 animals per treatment) and untreated cattle of the same age and breed from the same herd are examined monthly from August to February to the next year for encapsulated cattle grubs. As cattle grubs appear, they are located on an outline map of the back of each animal; the cumulative number of grubs in each animal is obtained. Effectiveness of treatment is determined by comparing the average number of grubs in treated cattle with the average number in untreated cattle.