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The use of organophosphorus preparations in the treatment of ectoparasites and endoparasites of pigs is discussed. Treatment of 43 store pigs with preparations produced in the German Democratic Republic by washing and by the pour-on method resulted in considerable inactivation of acetylcholinesterase, which implies good systemic action. Overdosage increased this effect, but without producing signs of toxicity. The oral dosages for pigs cited in the literature were confirmed. Repeated treatment was recommended for the best results, as pigs rapidly break down the preparations. It is necessary to take into account adverse effects of oral administration on palatability of the ration and on weight gain. Addition of a preparation to a batch of food for a group of pigs is likely to be less successful than individual dosing, which is the best method for sows.

The use of organophosphorus preparations for the control of ectoparasites and endoparasites of sheep, particularly systemic application, is discussed. Experiments on 13 groups of sheep with five preparations produced in the German Democratic Republic in various formulations and concentrations showed that external application had good contact activity, but little was absorbed. Acetylcholinesterase activity was not inhibited, except by pour-on application of doses several times the normal dose. The preparations were arranged in order of cholinesterase inhibition. In contrast to cattle, diminished cholinesterase activity was unreliable as in indicator of systemic toxicity of organophosphorus preparations in sheep.