Genetic characterisation of east African cattle breeds

• Sokoine University of Agriculture, Tanzania
• CSIRO Division of Tropical Crops and Pastures, Australia

Many indigenous livestock breed in the developing world are threatened with genetic erosion due to the importation of germplasm. East Africa has a complex history of successive introductions of Zebu and Sanga breeds over thousands of years, the legacy of which is a rich collection of indigenous cattle breeds of uncertain relationship to one another. This project aims to characterise a range of zebu, sanga and zebu/sanga cattle breeds in Australia, Kenya and Tanzania. The degree of genetic relatedness between breeds will be determined using DNA microsatellite and RAPD markers. Data on a variety of production characters with special emphasis on growth and tick resistance will be collected and/or collated in the three countries. It is anticipated that on the basis of the information obtained, it will be possible to draw conclusions on broad genetic and some specific production similarities/differences between a variety of cattle breeds relative to well characterised Brahman Breeds. The potential for identifying generic markers for production traits will also be assessed.

The delineation of the maps of genetic distance between cattle of different origins, using the newer molecular tools of DNA microsatellitesand RAPD markers, provided insights into the evolution of the different races of cattle, their likely productive and adaptive traits and the inheritance of those characteristics. In Australia samples from indigenous zebu breeds were compared to the improved Boran and N'Dama breeds in Africa and Tuli and Brahman descendants in Australia using DNA microsatellite variation . Most of these breeds show moderate to high levels of resistance to different parasites and are generally adapted to semi- and tropical environments. The analyses demonstrated that the largest genetic distance was found between the Sahiwal breed of Kenya and Hereford-Shorthorn x Tuli of Australia. The RAPD technique was applied on samples of African cattle breeds from Kenya and Tanzania only (Boran, Maasai zebu, Iringa red, Chagga zebu, Sukuma and Ankole zebu). The results of both analyses showed close similarity of the African breeds and their unrelatedness with a distant breed, the N'Dama The closest breeds being the Boran cattle from Kenya and Tanzania. A field study of the comparative susceptibilities of Boran and Maasai zebu cattle to tick infestation was conducted in Tanzania in the first year of the project. The results indicate a marked difference between the Maasai and Boran breeds in tick susceptibility, with the Boran, already imported into Australia, not as tick resistant as the Maasai zebu (which is probably more representative of indigenous East African zebu breeds).