Dispersal and concentration of sheep gastrointestinal nematode larvae on tropical pastures

Knowledge of free-living stages of endoparasite population ecology may guide their control in domesticated ruminants. Our objective was to evaluate sheep gastro-intestinal nematode (GIN) L3 distribution in tropical pasture profiles (grass and legume). Three different swards (treatments) were compared: 1) grass-only (G), 2) legume-only (L), and 3) one half of the paddock with grass and another half with legume (GL). We assessed pasture larval counts (PLC) in upper, medium and bottom strata, each representing one third of the sward height. Lamb health and performance characteristics were also evaluated. The PLC per kg of herbage dry matter (DM) tended to be 129% greater (P = 0.08) in the upper pasture profile compared to the lower stratum in GL pasture. However, the largest PLC dispersed per area (PLC/m²) was found (P