Genetic and immune responses characterization associated with the phenotype of parasite resistance in a sheep flock of Morada Nova

Abstract

Brazil has great diversity of exotic sheep breeds and their crosses, as well as hair-sheep breeds adapted to tropical conditions, as Santa Ines and Morada Nova. However, the gastrointestinal nematodes (GIN) are a major constrain in these production systems, in particular Haemonchus contortus, due to parasitic resistance widespread in the Brazilian flocks. In this way, economic losses are high due to the reduction in production, intensive use of dewormers and deaths. Hair breeds, such as Morada Nova, are more resistant to worms, which is an extremely important feature due to the impact of this disease in sheep production. Even in the pre- and post-partum periods, when GIN infections tend to increase significantly, the health of Morada Nova sheep is not affected. This breed also has as characteristics: hardiness, prolificacy, excellent leather quality, sexual precocity, maternal ability, lack of reproductive seasonality and excellent adaptation to tropical climate. In this way, the present project aims to characterize the Morada Nova flock from Embrapa Pecuária Sudeste in relation to its resistance, using phenotypic and genotypic tools, as well as to evaluate the immune responses to the main helminth of occurrence in Brazil, H. contortus. It is expected to reach a better knowledge of molecular markers for resistance to parasitic diseases in the breed and of the mechanisms of immune responses induced by H. contortus. The identification of cytokines, cells or other mediators directly related to resistance can be used to improving the immuno-prophylactic management of this disease and the development of recombinant vaccines. It would it be possible, in the future, to get generations of mating, with homogeneous populations with respect to its composition, to offer resistant Morada Nova animals to producers, encouraging the sheep meat production. (AU)