The estimation of genetic parameters allows for the accurate prediction of estimated breeding values (EBVs), which play a crucial role in developing selection indices used to generate genetic progress for economically important traits. This study aimed to estimate genetic parameters and EBVs for the South African Merino sheep breed. A population of 864 754 South African Merino sheep were included in this study. Pedigree information included animals born between 1919 and 2022, of which 457 757 (52.94%) were females and 406 996 (47.06%) were males. Variance components were estimated for all sheep born after 2009, consisting of 62 460 sheep. A multi-trait animal model was used to estimate the variance components, using VCE6 statistical software. Heritability values and standard errors were estimated for seven traits: direct weaning weight (0.25 ± 0.01), maternal weaning weight (0.20 ± 0.00), body weight at wool test (0.26 ± 0.01), clean fleece weight (0.33 ± 0.01), staple length (0.33 ± 0.00), fibre diameter (0.63 ± 0.00), and coefficient of variation of fibre diameter (0.43 ± 0.00). Using the same genetic models as used for variance component estimation, EBVs were predicted using PEST2. Genetic trends were determined by averaging the EBVs of the measured animals per year of birth per trait, and these were compared to the national trends provided by SA Stud Book. This study updates the variance components and EBVs of the South African Merino sheep breed, enabling the accurate genetic selection of animals and facilitating faster genetic progress.

(Submitted 3 November 2025; Accepted 24 March 2026; Published 19 May 2026)