Farm-Gate Prices as an Economic Signal of Foot-and-Mouth Disease Vaccination Performance in Hanwoo Cattle: A Nationwide Time-Lag Analysis

Background/Objectives: In mandatory livestock vaccination programs, post-vaccination immunity depends on both vaccine characteristics and consistent on-farm implementation. We evaluated whether Hanwoo farm-gate prices were temporally associated with subsequent foot-and-mouth disease (FMD) structural protein (SP) antibody seropositivity, used as a population-level proxy for vaccination performance. Methods: We analyzed 75,408 individual SP antibody records from Hanwoo cattle on commercial farms (≥50 head) sampled on-farm from April 2019 to December 2022 and linked monthly seropositivity to four price metrics. A separate 2022 cohort (n = 131,805) was analyzed by multivariable logistic regression. Cross-correlations assessed price-leading lags of 0–12 months; linear and exploratory hinge models evaluated association magnitude and a candidate breakpoint. Results: Overall SP seropositivity was 96.3%. Cattle from commercial farms had higher odds of antibody negativity than those from smaller farms (adjusted odds ratio [OR] 1.15, 95% confidence interval [CI] 1.05–1.26), whereas each additional recorded vaccination was associated with lower odds (OR 0.89, 95% CI 0.88–0.90). Monthly price and the 3-month moving-average price showed their strongest associations with subsequent seropositivity at 7 and 6 months, respectively (r = 0.519 and 0.506; both p < 0.001). Month-to-month price changes were not associated with seropositivity. An exploratory hinge model identified a candidate breakpoint near KRW 6.26 million per 600 kg live animal. Conclusions: Sustained farm-gate price conditions, rather than short-term volatility, were associated with subsequent FMD post-vaccination seropositivity. Livestock price data may provide a contextual signal for targeting communication and vaccination support activities; however, this ecological association does not demonstrate price-driven behavioral change at individual farms, and the candidate breakpoint requires prospective validation.