Population structure and genetic variability of the Segureña sheep breed through pedigree analysis and inbreeding effects on growth traits

- The Segureña sheep breed has sufficient genetic variability with appropriate levels of inbreeding as deduced by the lack of adverse effects on animal performance.
- The environmental effects represent an important source of variation on weight and average weight gain in the Segurenã sheep breed.
- The effective number was higher than the minimum suggested by FAO for the maintenance of genetic variability over the generations.

Pedigree information on 37,459 sheep of the Segureña breed was used to evaluate population structure, genetic variability and the inbreeding effect on growth traits. The relation between the effective number of founders/ancestors (1.12) indicates that the founding animals contributed throughout the entire breed-forming process. The low values obtained for inbreeding (0.60%) and average relatedness coefficients (0.06%) indicate genetic variability; however, these results might be related to the low pedigree depth observed through the number of equivalent generations (1.23). Fixation indices (F-statistic) and the absence of nucleus herds indicate that, despite the intense use of some rams, population subdivision was not observed in the breed (FST = 0.0183). Inbreeding depression was not observed on evaluated growth traits, with environmental factors, year-season-herd, type of birth and sex as primarily responsible for the observed variation.