Field evaluation of targeted selective treatments to control subclinical gastrointestinal nematode infections on small ruminant farms

Abstract

Targeted selective treatments (TST) are designed to identify those animals that would actually benefit from anthelmintic treatment, thus reducing the amount of drugs used and bringing down economic cost. In this study we assayed three TST programs based on GIN egg output, clinical sign and live weight criteria in a single area where only sub-clinical infections tend to occur and no anthelmintic resistance is reported. The study was carried out from February 2011 to August 2013 on four farms applying different management systems: an Ovine Extensive System, Ovine Semi-extensive Semi-irrigated System focusing on "Rubia del Molar" and Colmenareña" breeds, Ovine Semi-extensive System and Caprine Organic Semi-extensive System. The number of sheep and goats treated in all the TST strategies was lower in comparison with systematic treatments, especially when selected based on clinical signs (100%, in both years), followed by egg output (87.57% and 90.44% in the first and second year respectively) and finally by live weight (37.95% and 96.69%, in the first and second year respectively). FEC was low throughout the study for all animals and groups. Apparently, the TST applied did not influence live body weight. Preliminary results show that all three targeted selective treatments significantly reduced the number of animals treated and the cost of anthelmintic treatment on the farms, maintaining productivity in a low challenge environment. These results also seem to indicate that systematic anthelmintic treatments are unnecessary under these circumstances and traditional anthelmintic regimes should therefore be modified.

Keywords: Extensive management systems; Small ruminants; Subclinical gastrointestinal nematodosis; Targeted selective treatments.