Abstract
To find out the genetic basis of phenotypic differences of cattle populations in Bangladesh a molecular study using microsatellite, mitochondrial DNA D-loop region (863bp) and Y chromosome specific markers were carried out. In total 150 blood samples were collected from three different cattle populations namely Red Chittagong (RC, 43), Non-descript Local (NDL, 67) and North Bengal Grey (NBG, 40) covering throughout the country. Thirty three blood samples from indigenous draft population of Sri Lanka was also used as a reference sample. A total of 234 alleles were detected from 16 microsatellite loci. Microsatellite analysis revealed higher allelic (7.856±1.80) and gene diversity (0.717±0.01) indicating cattle populations in Bangladesh are fairly outbred. Mean number of alleles at each locus varied from 5 to 12 as markers were chosen from FAO recommendation. All population showed significant inbreeding effect (Fis=0.057; P<0.01) as well as significant deviation from Hardy-Weinberg Equilibrium, but no recent bottleneck was found in any of the populations. These suggest non-random mating and possibly natural or artificial selection are being practiced in the small herds of cattle. Phylogenetic analysis showed that RC and NDL population form one cluster whereas NBG population placed in another cluster indicating different genetic structure of NBG. Presence of taurine male specific alleles has made NBG population distinct from RC and NDL population which was supported by Y-chromosome specific locus study. A hierarchial analysis of molecular variance indicates that genetic variation among cattle population of Bangladesh is low (0.09 % to 1.14%). Mitochondrial DNA, 863 bp of D-loop study shows low average nucleotide diversity (0.0060±0.001) which is not an indication of an endangered species. Higher number of identified haplotypes (41 out of 93 sequences) suggests that many female founder animals have been involved in the formation of Bangladeshi cattle population. Non significant maternal genetic differentiation among three populations at nucleotide level implies that separation is rather male based. Therefore, for conservation purposes and in making breeding strategies RC, NDL and NBG population should be regarded as different types or varieties but not necessarily as separate breed, unless other arguments related to practical management favor more stringent separation.