Integrated assessment of the reproductive performance of ewes of different genetic origins considering animal welfare indicators, Інтегрована оцінка відтворювальної здатності вівцематок різного генетичного походження з урахуванням показників благополуччя

<jats:p>The article investigates the peculiarities of reproductive performance formation in ewes of different genetic origins under modern intensive sheep production systems. The relevance of the study is determined by the need to improve flock reproductive efficiency through the combination of genetic resources, the enhancement of breeding strategies, and the consideration of animal welfare indicators. It was established that genetic origin significantly affects fertility, prolificacy, and lamb output. Crossbred genotypes Dorper × Romanov and Merinoland × Romanov outperformed purebred Dorper sheep in most reproductive traits, demonstrating the manifestation of heterosis effects. The highest fertility rate (92.3 %) was recorded in the Dorper × Romanov group, whereas the greatest prolificacy (161.1 %) was observed in Merinoland × Romanov ewes. The results showed that crossbred animals were characterized by higher milk production (5.7–9.6 % increase), lower incidence of diseases and stress load, and better behavioral activity indicators, suggesting a higher level of animal welfare. At the same time, the highest lamb survival rate was observed in purebred Dorper ewes (90.9 %), whereas a slight decrease was recorded in crossbred groups due to their increased prolificacy. The Integrated Reproductive Ability Index (RAI) in the experimental groups ranged from 0.73 to 0.91 conventional units. The highest values were obtained in the Merinoland × Romanov group (+24.7 % compared with Dorper), indicating the most complete realization of genetic complementarity and an optimal balance between productivity and adaptability. The scientific novelty of the study lies in substantiating a systematic approach to evaluating reproductive performance based on the integration of genetic, productive, and animal welfare indicators. Therefore, the proposed Integrated Reproductive Ability Index (RAI) provides a comprehensive evaluation by combining fertility, prolificacy, lamb survival, milk production, and animal welfare indicators into a single integrated criterion. It can be recommended as an additional selection criterion for identifying breeding ewes with high reproductive efficiency and adaptive potential. The practical application of the Integrated Reproductive Ability Index (RAI) enhances the objectivity of breeding genotype selection, optimizes breeding programmes and flock reproduction, and contributes to the implementation of sustainable sheep production in accordance with the principles of the Animal Welfare, One Welfare, and One Health concepts.</jats:p>