Abstract: [Objective] This study analyzed 416 739 breeding events from heifers across 144 dairy farms and 1 193 209 breeding events from dairy cows across 152 dairy farms recorded between 2023 and 2024. The objective was to determine conception rates associated with different intervals between Foot-and-Mouth Disease （FMD） vaccination and breeding. [Methods] Breeding events were grouped based on the interval in days after FMD vaccination. Conception rates were calculated for each group as the proportion of breeding events resulting in a confirmed pregnancy relative to the total breeding events with a known pregnancy diagnosis outcome. Conception rates were compared between interval groups. [Result]（1）For heifers vaccinated >30 days before breeding,the conception rate was 60.3%. Conception rates for heifers bred 0~5 days and 6~10 days post-vaccination were 56.0% and 58.4%,respectively,representing decreases of 4.3 and 1.9 percentage points compared to the >30-day group. The decrease was most pronounced in the first service （4.4 percentage points） and second service （4.9 percentage points）.（2）For dairy cows vaccinated >30 days before breeding,the conception rate was 41.9%. Conception rates for dairy cows bred 0~5 days and 6~10 days post-vaccination were 39.4% and 41.1%,respectively,across all parities.（3）Vaccination given 0~5 days and 6~10 days before breeding significantly reduced the conception rate in primiparous cows,resulting in decreases of 3.7 percentage points and 2.6 percentage points,respectively. （4）Vaccination 0~5 days before breeding had a significant negative impact on conception rates at the first service,causing a decrease of 3.1 percentage points. [Conclusion] To enhance precision reproductive management,dairy farms should strategically schedule FMD vaccination programs and optimize vaccination timing relative to breeding. This can minimize negative impacts on reproductive performance and maximize disease prevention benefits. Implementing refined breeding strategies considering vaccination timing can further improve conception rates and reduce labor and frozen semen costs.

Key words: dairy cattle, vaccination, breeding, conception rate