Targeted application of anthelmintics to control trichostrongylosis in dairy goats: result from a 2-year survey in farms

The targeted application of anthelmintic treatments represents one of the current available solutions to slow down the development of anthelmintic resistance within worm populations. Within an experimental flock of dairy goats, control of gastrointestinal parasitism by such selective treatments, targeting the most receptive animals within a flock, was previously found to be effective and to have no detrimental consequences on milk production. The objectives of the current study were to verify the validity of this method in farm conditions. Eleven dairy goat farms from three main areas of production in France were surveyed for 2 years. In six farms, the survey was prolonged for a third year. During year 1, systematic treatments were applied during the grazing season whereas in year 2 and or year 3, treatments were given exclusively to the goats in first lactation and to the multiparous ones with the highest potential of milk production. The level of nematode infection was measured four times per year through individual coproscopical examinations and the mean annual production of milk was recorded. No significant changes in egg excretion nor in milk production were noticed in any farm during years 2 or 3 after switching from the systematic to the selective mode of treatments. These results confirmed that targeted application of anthelmintics might represent a way to combine the control of trichostrongyles and the prevention of anthelmintic resistance. (C) 2002 Elsevier Science B.V. All rights reserved.