Th is study was aimed at the meta-analysis of the conception rates to the first insemination of dairy cattle treated with the Ovsynch protocol, and the determination of the sources of heterogeneity between the studies included in the analysis. Th e study material comprised of 46 primary studies conducted between 1999-2019 on the use of the Ovsynch protocol in Türkiye. Th e heterogeneity between these studies was assessed by meta analysis using the random-eff ects model and the Der Simonian-Laird method. Accordingly, the common conception rate to the first insemination calculated for the primary studies, in which dairy cattle were treated with the Ovsynch protocol, was 0.412 (95% CI: 0.384-0.442) (P<0.001). Th e source of heterogeneity between the primary studies was determined by subgroup analyses. Conception rates were calculated for subgroups, which were established for geographical region, cattle breed, year of publication and parity. While the conception rates significantly diff ered for geographical region, the diff erences observed for cattle breed, year of publication and parity were statistically insignificant. When assessed for geographical region, the lowest common conception rate was determined in the Eastern Anatolia region (26%), whilst the highest common conception rate was determined in the Black Sea region (51.6%). Th e common conception rates calculated for cattle breed were 41.3% for Holstein cattle and 43.6% for Brown Swiss cattle. It was observed that the conception rates had decreased by 10% in the last 20 years to a level of 40.2% in the period between 2015 and 2019. Th e common conception rates calculated for parity were 39.4% for heifers and 41.9% for multiparous cows. It is considered that the results obtained in this study will contribute to the development of new strategies for a rational production in the dairy sector.