Genetic diversity and zebu genes introgression in cattle population along the coastal region of the Bight of Benin

Abstract

Genetic diversity and Zebu genetic introgression have been assessed in five subpopulations of cattle along the coastal region of Togo, Benin and Nigeria using 15 autosomal and one Y- specific microsatellite markers. Mean observed heterozygosity (Ho) ranges from 0.55 to 0.61 and the mean number of alleles (MNA) from 5.47 to 6.47. Genetic differentiation indexes (Fst), were significant between the five subpopulations (P< 0.01). Some possible population diagnostic alleles are identified with allele 254 at locus ILSTS033 and allele 182 at locus ILSTS005 found only in the population from Togo with frequencies of 5.41% and 12.82% respectively. Allele 226 of locus ILSTS103 is fixed in the Togolese population (100%) and almost fixed (98.75%) in the Benin-Valley population. Y chromosome analysis reveals male Zebu introgression in all five populations with a frequency of indicine Y chromosome ranging from 37.5% in Benin-Valley and Benin Plateau East to 100% for Benin Plateau West. Admixture analysis using the programme STRUCTURE (k = 2) confirms phenotypic observations suggesting different level of taurine background and therefore Zebu introgression amongst the populations. Within populations, variations in levels of Zebu admixture between herds were also detected. Whereas the valley population from Benin shows low level of Zebu introgression, it is the population from Benin Plateau East which is the purest.