The study was conducted to evaluate the factor affecting calving interval of dairy cows in central highlands of Ethiopia. The retrospective study was conducted on 682 cows (crossbred & local cows). Statistical analysis performed using the GLM procedure of SAS 2001, showed significant differences in calving interval value within different factors. The result of analysis of variance showed variations of breed, parity, management systems and AI technicians had a significant (p 0.05) effect on the length of calving interval The overall mean of calving interval obtained in this study was 568.50 days. The result also showed that calving interval of local breeds (611.92+2.0) of cows was greater than crossbreed cows (525.08+1.7). Furthermore, the result showed that the length calving interval of heifers (648.61+8.3) is higher than first (560.08+3.6), second (542.01+3.3) and third (523.31+2.6) parity of cows. In addition, cows managed under extensive management system (592.54+3.0) were higher number of service per conception than intensive management system (544.47+2.2). Generally, it can be inferred that length calving interval decreased by better feeding, heat detection or time of insemination and management of cows is essential.
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