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Various factors are believed to influence quality of semen in breeding bulls. The main objective of this study was to evaluate how breed, age and time of semen production are relevant in the production of good quality semen used for Artificial Insemination. A total of 16,827 ejaculates from 187 bulls (Holstein Frisian = 114, Jersey = 35, Borena = 12, 50%HF × 50%Borena = 5, 75%HF × 25%Borena = 15 and Fogera = 6) were collected and examined at the National Animal Genetic Improvement Institute (NAGII). All these factors (breed, age and period of production) had significant (p ≤ 0.05) effect on semen volume, colour, concentration, mass activity, individual motility and production doses/ejaculate. All these semen quality measures were significantly (p ≤ 0.05) minimal in 50%HF × 50%Borena crosses and all of them except concentration were observed superior in HF. Excluding ejaculate volume and production doses, all the semen quality measures were recorded better in the first two age classes (less than 2 and 2 to 4 years of age classes). Significance differences in ejaculate volume, concentration, mass activity, and individual motility were observed among production periods; these disparities could be due to the variation in managemental practice and efficiency of implementing the protocol in selecting candidate bulls for the time period. In conclusion, breed, age and period of semen production have significant effect on bovine semen characteristics. Key words: Borena, cross breeds, Fogera, Holstein Frisian, Jersey, semen characteristics.

At present, frozen-thawed semen is used extensively for artificial insemination (AI) in Ethiopia. However, subjective semen quality assessment is still practiced by the semen processing organizations of the country. In this study, motility and motion characteristics of spermatozoa were assessed by using integrated semen analysis system (ISAS) to diagnose breed differences in quality of semen. Semen was collected from 14 breeding bulls (Boran = 4, Crosses of 75 % Holstein Frisian EŸ 25% Boran = 4 and Holstein Frisian = 6). After initial subjective assessment, the semen was evaluated at fresh, chilled and frozen stages for various sperm motion characteristics using integrated semen analysis system (ISAS® v1, Proiser, Spain). PH, volume and morphological defects were differed significantly (P < 0.05) among breeds. Significantly higher (P < 0.05) motility percentage (82.5%) was identified in Boran fresh semen. In contrast spermatozoa motion characteristics: Medium, medium progressive and slow types were significantly higher (P < 0.05) in crosses. Individual motility percentage and spermatozoa motion types (medium and slow) were significantly low (P < 0.05) in Boran chilled semen. In line with chilled semen significantly high motility percentage (42.9%) for frozen semen was observed in HF. The sperm kinematic parameters: Average path velocity (VAP, µm/s), straight line velocity (VSL, µm/s), curvilinear velocity (VCL, µm/s), amplitude of lateral head displacement (ALH, µm), beat cross frequency (BCF, Hz) and straightness (STR) percentage were differed significantly (P < 0.05) among the three breeds at all stages of semen production. The smallest kinematic values of all parameters except for LIN, STR and WOB of fresh semen were recorded in cross breed bulls at all stages of production. On the other hand significantly higher (P < 0.05) values for all the parameters (VCL, VAP, VSL, ALH, BCF, LIN, STR and WOB) of frozen semen were recorded in Boran breed. Thus it is possible to conclude that breed has influence on motility and motion characteristics of bull spermatozoa at different stages of semen production. Key words: Boran, Integrated Semen Analysis System (ISAS), kinematic parameters.