Chronic Toxicity of Dimethoate to Hens1

Abstract

The effects of administering technical and emulsifiable dimethoate at a concentration of 30 p.p.m. in the drinking water of laying hens were studied over a 59-week period. The estimated mean daily intake of the technical and emulsifiable dimethoate was 0.010 g. and 0.0092 g., respectively. These treatments resulted in excellent larval control of Musca domestica L, Fannia pusio (Wiedemann), Chrysomya megacephala (F.), and Parasarcophaja argyrostoma (Robineau-Desvoidy) in the droppings from these hens. Some hen mortality occurred owing to an accidental over dosage in the emulsifiable dimethoate treatment at the start of the experiment, but excluding these accidental deaths, no mortality occurred which could be attributed to the dimethoate. Plasma cholinesterase activity was rapidly inhibited by the treatments but recovery was also rapid after removal from treatment. Overall feed consumption and gains in weight were reduced, especially by the emulsifiable dimethoate treatment. Egg production, on the other hand, despite an initial depression was normal in the technical dimethoate-treated animals and higher in the emulsion-treated hens than in the untreated hens. The treatments had no detrimental effects upon shell thickness or egg weight and had a significantly beneficial effect upon interior egg quality. Eggs from treated hens had no detectable off-flavors,-odors,-texture, or-color.