Trypanotolerance and the value of conserving livestock genetic resources

Abstract

Studies have been made in two main areas of genetic research on African trypanotolerant (N'Dama) cattle. The first is of the significance for performance and the heritability of trypanotolerance traits and the second is the search for markers of the breed type and the traits of interest. Results demonstrate significant effects of the ability of an animal to control parasitaemia and anaemia on its performance. Initial estimates suggested that parasitaemia measures had a very low heritability, but ability to maintain packed cell volume levels when detected as parasitaemic and to generate an immune response could form the basis of a practical selection approach. The search for markers has so far concentrated on the major histocompatibility complex and on a polymorphic system of common leukocyte antigens. Phenotypes that appeared more characteristic of the N'Dama in comparison with those of East African zebu cattle were examined for associations with trypanotolerance traits. One major histocompatibility complex encoded phenotype and two common leukocyte antigens gave indications of important associations. Planned research will further characterise the breed and define traits of importance to assist in increasing its productivity in Africa and thus in its conservation. The addition of a molecular genetics component to an integrated genetics research programme, principally through involvement in development of a linkage map of the bovine genome, will strengthen these efforts and make it possible to conserve specific N'Dama genes related to productivity.