In Partial Fulfillment of the Requirement for the Degree of Master of Veterinary Reproduction and Obstetrics.

Abstract

The low productivity of Ethiopian indigenous cattle can be improved through selection and crossbreeding with high-producing exotic breeds. This study aimed to evaluate the effects of age and breed on bull semen quality at the Regional Artificial Insemination Center (RAIC). A total of five Holstein Friesian (HF) and Begait bulls aged 3-9 years were used. Semen was collected using an artificial vagina, and evaluations were conducted using a photometer, stage heated microscope and eosin-nigrosin staining for sperm viability and abnormality assessments. Independent sample t-tests were employed to compare semen quality parameters between groups. The results indicated no significant differences (p > 0.05) between HF and Begait bulls in motility, concentration, and viability, except for semen volume, which was significantly higher in HF bulls (p = 0.001). The highest initial motility (78.75 ± 1.35%), concentration (1.75 ± 0.15), and live sperm count (81.00 ± 0.85%) were observed in bulls aged 4-6 years. Lower values were recorded in younger (< 4 years) and older (> 6 years) bulls. Progressive forward motility was negatively influenced by defective sperm cells (13.1 ± 1.4%), with tail abnormalities significantly affecting semen quality (p < 0.05). Minor sperm defects (10.6 ± 1.2%) were more prevalent than major defects (2.5 ± 0.2%), with bent-tail defects being predominant. Post-war conditions led to a significant increase in defective sperm cells, potentially due to aging and seasonal variations. The study concludes that age significantly affects semen quality, while breed does not. Introducing younger, proven bulls into breeding programs is recommended to enhance fertility rates and semen quality.