Abstract
<title>Abstract</title> <p>This study assessed bull semen quality and the efficiency of field artificial insemination (AI) services in Aira and Gulliso districts, West Wollega Zone, Oromia, Ethiopia. A retrospective survey involving 138 respondents was conducted using a structured questionnaire to evaluate AI service delivery and identify factors affecting reproductive performance. Laboratory analyses of frozen semen samples were performed at the National Animal Genetic Improvement Institute (NAGII), Kaliti, to assess semen quality and determine potential causes of reduced AI efficiency. The retrospective analysis showed that AI efficiency was not significantly influenced by year, although conception rate differed significantly among breeds, insemination seasons, and years (P < 0.05). The number of AI users and successful pregnancies increased over the study period. The major constraints affecting AI services included inadequate technician performance, conception failure, and delayed semen availability. Laboratory evaluation demonstrated that frozen semen stored at NAGII had significantly higher post-thaw motility, sperm viability, and lower morphological defects than semen obtained from district AI centers (P < 0.005). Semen collected from mature bulls (4–6 years) exhibited superior volume, concentration, and mass motility compared with that from younger bulls. The findings indicate that improper semen handling, transportation, and storage at district level compromise semen quality and AI efficiency. Strengthening cold-chain management and improving technician competency are essential to enhance reproductive performance and the effectiveness of AI programs.</p>