The article presents the results of a study on the phenotypic variability and approximate heritability of major economically useful traits in Kyrgyz Mountain Merino sheep bred in the foothill zones of the Western Tien Shan. The material comprised data from long term sheep recording (bonitation), production indicators, and the results of the authors' own surveys of livestock at state breeding farms of the Kyrgyz Research Institute of Animal Husbandry and Pastures for the period 2015–2025. Traits of wool productivity (fleece weight, fiber fineness, and fiber length) and meat productivity (live weight) were analyzed, along with selected exterior characteristics. Phenotypic variability was assessed using the coefficient of variation, which made it possible to identify the degree of trait stability and the presence of a selection reserve across within breed types. Approximate heritability was estimated from variance components based on one way analysis of variance and was used for a comparative characterization of the genetic determination of traits within the breed. It was established that wool traits are characterized by varying degrees of variability and heritability. Fiber fineness exhibits the highest breeding value, while fiber length and fleece weight show moderate heritability. Meat and exterior traits display moderate variability and a moderate level of heritability, which justifies their use primarily in line breeding systems. The results obtained confirm the expediency of taking variability and heritability estimates into account when adjusting breeding programs for the improvement of the Kyrgyz Mountain Merino breed
Keywords
Kyrgyz Mountain Merino, variability, heritability, coefficient of variation, wool productivity, breeding