A review on omics approaches, towards understanding environmental resilience of indigenous Nguni sheep: Implications for their conservation and breeding programs in South Africa

Genetic heterogeneity, as the driver of evolutionary potential and counterbalance to inbreeding depression, is an important consideration for ensuring livestock adaptability, robustness and resilience to erratic and challenging environments. Accordingly, the low genetic diversity within exotic livestock breeds may suggest survival uncertainty and extinction risk, as agroecological environments are consistently changing due to global climate change. Indigenous livestock breeds, such as the southern African Nguni sheep, have been reported to be genetically and phenotypically diverse and adapted to their local environmental adversities, including high temperatures, drought, and diseases. Characterising and understanding the molecular determinants underpinning their robustness may assist in selecting and breeding for highly productive livestock progeny that are resilient to a broader spectrum of environmental challenges. Also, understanding indigenous livestock breeds genetic uniqueness will further emphasize their significance as a valuable genetic resource and strengthen the impetus for their conservation. This review first reiterates the concept of southern African indigenous sheep ecotype (Nguni sheep) as a valuable genetic resource for future breeding programmes against local environmental adversities, and further discuss the importance of understanding the genetic mechanisms underpinning their adaptative traits to southern Africa which have not been adequately explored. Some of the previously reported genes, associated with indigenous sheep breeds adaptation to southern African environments includes: MYH9 (energy metabolism), PITIX1(high altitude adaptation), CREB3L2, CREB3, GNAQ, DCTN4 (thermoregulation), EGLN1, EPAS1 (hypoxia associated genes). Finally, we highlighted contemporary omics techniques, commonly used in livestock genomic studies, that may assist in revealing the genomic basis of Nguni sheep unique genotypes of environmental resilience.