Survival of Haemonchus contortus larvae in forage species in the Eastern Amazon

Abstract

The objective of this work was to evaluate the survival of third-stage larvae (L3) of Haemonchus contortus in forage species in the Eastern Amazon. Four paddocks composed of Megathyrsus maximus 'Massai', M. maximus 'Mombaça', Urochloa brizantha 'Marandu', and Urochloa humidicola were used and divided into 13 plots each. Sheep feces containing about 10,000 eggs of H. contortus were deposited in each plot. Grass, feces, and soil samples were collected on the seventh, fifteenth, and thirtieth day post-contamination (DPC), and, then, they were sequentially collected every 30 days until the three-hundredth and thirtieth DPC. The following data were determined for the grass species: microclimatic, such as temperature, relative humidity, soil moisture, and grass luminosity, as well as macroclimatic data for rainfall, temperature, relative humidity, and solar radiation. L3 were recovered on all grasses and soil samples, in all plots, from the seventh to the three-hundredth and thirtieth DPC. The microclimatic parameters show correlations between the L3 recovery on grass and in the soil, and the macroclimatic parameters, between the L3 recovery in feces and on grass. Urochloa humidicola and M. maximus 'Massai' favor the development and survival of L3 of H. contortus, while U. brizantha 'Marandu' and M. maximus 'Mombaça' show a lower bioavailability of these larvae.