The genetic history of African cattle pastoralism is controversial and poorly understood. We reveal the genetic signatures of its origins, secondary movements, and differentiation through the study of 15 microsatellite loci in 50 indigenous cattle breeds spanning the present cattle distribution in Africa. The earliest cattle originated within the African continent, but Near East and European genetic influences are also identified. The initial expansion of African Bos taurus was likely from a single region of origin. It reached the southern part of the continent by following an eastern route rather than a western one. The B. indicus genetic influence shows a major entry point through the Horn and the East Coast of Africa and two modes of introgression into the continent.

We report for the first time, and for the whole of sub-Saharan Africa, the geographical distribution and the frequency of an indicine and a taurine Y specific allele amongst African cattle breeds. A total of 984 males from 69 indigenous African populations from 22 countries were analysed at the microsatellite locus INRA 124. The taurine allele is probably the oldest one on the continent. However, the taurine and the indicine alleles were present in 291 males (30%), and 693 males (70%), respectively. More particularly, 96% of zebu males (n = 470), 50% of taurine males (n = 263), 29% of sanga males (crossbreed Bos taurus x Bos indicus, n = 263) and 95% of zebu x sanga crossbred males (n = 56) had the indicine allele. The Borgou, a breed classified as zebu x taurine cross showed only the zebu allele (n = 12). The indicine allele dominates today in the Abyssinian region, a large part of the Lake Victoria region and the sahelian belt of West Africa. All the sanga males (n = 64) but only one from the Abyssinian region had the indicine allele. The taurine allele is the commonest only among the sanga breeds of the southern African region and the trypanotolerant taurine breeds of West Africa. In West Africa and in the southern Africa regions, zones of introgression were detected with breeds showing both Y chromosome alleles. Our data also reveal a pattern of male zebu introgression in Mozambique and Zimbabwe, probably originating from the Mozambique coast. The sanga cattle from the Lake Victoria region and the Kuri cattle of Lake Chad, cattle populations surrounded by zebu breeds were, surprisingly, completely devoid of the indicine allele. Human migration, phenotypic preferences by the pastoralists, adaptation to specific habitats and to specific diseases are the main factors explaining the present-day distribution of the alleles in sub-Saharan Africa.

No abstract

To evaluate the Weitzman approach for assessing alternative conservation strategies for breed ( population ) diversity, we used genetic distance measures between 49 African cattle breeds divided into two groups of 26 taurine ( Bos taurus ) and sanga ( Bos taurus×Bos indicus ) breeds and 23 zebu ( Bos indicus ) and zenga ( sanga ×Bos indicus ) breeds. The derived maximum‐likelihood trees clearly displayed the geographic distribution and the zebu‐taurine admixture of the breeds. We developed a novel scheme to estimate the extinction probability for each breed which considered total population size, change of population size over the last 10 years, distribution of the breed, risk of indiscriminate crossing, organization among farmers, establishment of conservation schemes, political situation of the countries, special traits, sociocultural importance, and reliability of information. This scheme yielded reasonable estimates of extinction probabilities for the analyzed breeds, which were significantly influenced by the population size and its recent change, distribution of the breed, organization among farmers, establishment of conservation schemes, and reliability of information. The average extinction probability over all breeds and for each breed group was around 48%. Diversity in the zebu‐zenga group was only half the diversity in the taurine‐sanga group, mainly because of the lower number of breeds and their genetic origin. For both groups, the expected diversity after 20–50 years was about half the current diversity, and the coefficient of variation was about 20%. Our results suggest that the optimum conservation strategy is to give priority to those breeds with the highest marginal diversity, rather than to the most endangered breeds; thus, Madagascar Zebu and Muturu should be given conservation priority in their respective groups. Our study demonstrates that efficient conservation of genetic diversity with limited funds has to take genetic and nongenetic factors into account. Nongenetic factors are accounted for within our scheme to derive extinction probabilities. Within‐breed and within‐population diversity are not accounted for. Extending Weitzman's basic approach accordingly could yield an effective methodology for determining conservation strategies under highly varying circumstances and for many species, including wild organisms.

SummaryThis paper summarises preliminary results of a survey conducted as part of a large effort to systematically collate information aimed at assessing the status of cattle genetic resources of sub-Saharan Africa. The 146 indigenous breeds/strains identified from the survey are classified into nine broad groups (Humpless Longhorns, Humpless Shorthorns, Large East African Zebu, Small East African Zebu, West African Zebu, Sanga, Zenga, Recently Derived Breeds and Commercial Composites) some of which are further subdivided into several groups (based on possible genetic relationships) and clusters (based on eco-geographical locations). Each breed is then described in terms of location, physical characteristics, adaptive attributes, if known, current main uses and status in terms of qualitative or quantitative indication of trends, where available, and presence or absence of programmes for its management or further development.