Study of the impact of gastrointestinal nematodes infection on the performance of Morada Nova Lambs for development of a targeted selective treatment

Abstract

Brazil has great diversity in livestock, and the sheep flocks are endowed with different regionalized breeds and crosses with exotic breeds, appropriately adapted, such as Texel, Ile de France, Suffolk and Dorper. Besides these, there are still the hair sheep breeds, like Santa Inês and Morada Nova, from the arid region of the northeast of Brazil. However, gastrointestinal nematodes (GIN) are a major threat to these production systems, especially Haemonchus contortus, the prevalent specie in Brazilian herds. Economic losses are high due to decreased productivity, expenses with anthelmintics, and mortality. Among brazilian breeds, the Morada Nova proves to be quite resistant to verminosis, even in the pre and postpartum periods. This breed also presents: rusticity, prolificacy, quality skin, sexual precocity, excellent maternal ability, lack of reproductive seasonality, and adaptation to the tropical climate. In view of these factors, the present project aims to adapt a method for sheep deworming through a targeted selective treatment (TST) approach, taking production parameters into account, such as the means of daily weight gain of the lambs (Happy FactorTM). This strategy seems to be more adequate than the FAMACHA© method, since Morada Nova lambs usually maintain high packed cell volumes even when highly infected. We intend to verify the possibility of detecting the most infected animals, optimizing their weight gain and reducing GIN contamination on the pasture, maintaining representative refugia (parasite population with no exposure to anthelmintics), minimizing the selection of resistance alleles. Thus, it is expected to make this information available to sheep producers in order to encourage the creation of the Morada Nova breed. (AU)