Analysis of genetic diversity in latvian darkheaded sheep population

The purpose of this study is to evaluate the parameters of genetic diversity, the level of inbreeding and effective population size based on pedigree data in genetic resources Latvian Darkheaded Old Type (LTV) sheep breed population. The study was based on genetic resources rams and ewes pedigree data that were alive in 2020. The pedigree data is available from 1976 with a total number of animals 2295 - 1817 (407 rams and 1410 ewes) with and 478 without progeny. Starting from the 2000 four generations completeness progressively increased and was higher than 70 %. In 2020, the pedigree completeness (PC) for the first generation was 100 % and for the fourth generation was around 90 %. The average number of generations in the LTV pedigree for inbreed animals is 10.2 +/- 0.07 generations. The number of inbreed animals in data set was 1177 with an average inbreeding coefficient 2.75 %. A positive change was found in the population of alive animals, where the level of inbreeding decreased and reached 2.36 %, however, 7.4 % of alive animals have a level of inbreeding greater than 5 %. The number of Ne in the LTV population within the last five years (2015 - 2020) is decreasing from 124 and in 2020 reached 108 animals. The changes in genetic diversity of the LTV population are explainable due to the greater restrictions in the LTV breeding programme, where from 2015 only purebred animals with 100 % LTV were accepted as genetic resources or the LT old-type sheep breed.