Abstract
Ethiopia is home to a diverse gene pool of indigenous sheep populations. Therefore, a better understanding of genetic variation holds the key to future utilization through conservation. Three of these breeds, Afar, Blackhead Somali, and Hararghe Highland, are found in eastern Ethiopia where they contribute significantly to the livelihood of most pastoralist, agro-pastoralist, and smallholder farmers. These indigenous sheep are recognized on the basis of morphotype and their genetic distinction remains unknown. Here, to assess genetic variation, and matrilineal genetic origin and relationship of fat-rumed sheep found in eastern Ethiopia, 300 individuals from the three breeds were genotyped for 22 microsatellite markers and sequenced for the mitochondrial DNA displacement loop (mtDNA d-loop) region. The overall HO and HE were 0.57 and 0.75, respectively. Differentiation statistics revealed that a high proportion (97%) of the total genetic variation was explained by differences between individuals within populations. Genotype assignment independent of the population of origin showed K = 2 to be the optimum number of genetic backgrounds present in the dataset. This result was further confirmed by mtDNA D-loop sequences comparison in which the matrilineal genetic origin of eastern Ethiopia sheep is from two haplotype groups (types A and B) among the five haplotypes globally observed. Taken together, our findings suggest that the sheep populations from three breeds originated from two ancestral genetic backgrounds that may have diverged prior to their introduction to Ethiopia. However, to obtain a complete picture of the evolutionary dynamics of Ethiopian indigenous sheep, more samples and populations from within and outside of the country will need to be analyzed.
Highlights
Animal genetic resources are critical for global food security and livelihoods
Results from the STRUCTURE analysis revealed that varying the number of presumed ancestral populations (K) produces clusters that are consistent with matrilineal genetic origin of eastern Ethiopia sheep
AFR sheep found in Amibara and Black Head Somali (BHS) found in Shinile are the only sheep populations that showed a relatively low level of admixture which is supported by relatively high FST value between them
Summary
Animal genetic resources are critical for global food security and livelihoods. Livestock products have high densities of energy, protein, and other critical nutrients, which are necessary for infants and expectant mothers (Boettcher et al 2014). In Ethiopia, changes in the demand for livestock products have been driven by human population growth, income increment, and expansion of urbanization. A large export and domestic market for mutton and live animal has created opportunity for sheep production in Ethiopia. The strategic location of Ethiopia to the Middle East is an opportunity to export meat (largely from sheep and goats) and live animals to these countries. The major sources of sheep exports (live animal and mutton) are from eastern lowlands of Ethiopia. In eastern Ethiopia, the Afar (AFR) and Black Head Somali (BHS) sheep are the predominant fat-rumped sheep populations that are distributed in arid and semi-arid areas (Gizaw et al 2007), while Hararghe highland (HHL) sheep is found in the highland where a croplivestock mixed farming system is practiced (Shibabaw et al 2014). The same sheep populations have been known for their adaptive traits such as resistance to disease, utilization of lowquality feed, and survival in harsh environments (tolerance to drought) (Nigussie et al 2015)
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