Genealogical structure and genetic variability: A step towards conservation of white Morada Nova sheep in semi-arid region

Abstract

Morada Nova breed has a low effective herd, and its white variety is in risk of extinction in Brazilian semi-arid region. This study aimed to evaluate white Morada Nova sheep’s genetic variability and population structure in four flocks. These are the only flocks in the world. The assessed parameters of pedigree integrity and a genealogy record of 219 animals. 44.74 % did not have pedigree information on their mother or father, and 50.47 % did not have available information on their grandparents. 52.97 % had a pedigree in their first ancestry (obtained through the average of known parents), 23.74 % in the second, 13.58 % in the third, and 5.33 % in the fourth. The effective size was 10.7, considering the complete equivalent generation. The effective number of founding animals (fe) and ancestors (fa) was 10, indicating the effective participation of all founding animals in the population over the generations, reducing losses of genetic variability. Out of all the ancestors, only 3 explained 50 % of the population’s genetic variability, reflecting the low values of fa and fe. The population’s average inbreeding and kinship coefficients were 2.61 and 4.54. The F statistics of Wright, Fis, Fst, and Fit, were −0.012, 0.016, and 0.003. The genetic conservation index (GCI) had an average of 2.01 ± 1.29, with minimum and maximum values of 1.0 and 6.38, respectively. Approximately, 71 % of the population had GCI below 2.0, while only 5.9 % of sheep had an GCI bigger than 5.0. This indicates the absence of sub-structures inf the population. There is no population subdivision, considering the genealogical structure of the evaluated flocks. The inbreeding and kinship coefficient values are controlled and serve as a starting point for establishing a future management plan for the genetic variability of the flock. It is recommended to use strategies to increase the effective population size, to meet the minimum number recommended by FAO and to promote the conservation and genetic improvement of the breed.