The Analysis of Paratuberculosis Prevalence and Associated Performance Parameters in Dairy Cows from Xi'an City

The aim of this study was to understand the status of Mycobacterium paratuberculosis infection in a large-scale dairy farm in Xi'an city and evaluate the impact via a "quarantine + elimination" model of bovine paratuberculosis on the production performance, reproductive performance, and economic benefits in said dairy farm. The paratuberculosis antibodies from 4488 dairy cow sera were detected by an ELISA kit, complemented by a comprehensive analysis of milk production parameters, health metrics, reproductive indices, and pharmaceutical expenditures (2021-2024). The results indicated that the paratuberculosis prevalence in the dairy farm gradually reduced from 6.76% (2021) to 3.58% (2024). It was also found that the paratuberculosis prevalence among dairy cows increased progressively with the increase in parity until the fifth calving, after which a significant decline was observed. The reduction in infection rates in the herd was correlated with measurable improvements in milk quality metrics, including elevated milk fat and protein content, extended shelf stability, and decreased somatic cell counts in milk. In addition, the reproductive performance of the dairy cows relatively improved with the decrease in paratuberculosis prevalence; there was a relative improvement in the reproductive performance of the dairy cows, which mainly occurred by the time of pregnancy at the first service of the cows, while the number of monthly occurrences of endometritis, diarrhea, calving intervals, and inseminations decreased. Further data correlation analysis showed that daily milk volume was positively correlated with lactase persistence (95% CI: 0.247-0.753, p = 0.001) and peaked at the day of milk production (95% CI: 0.135-0.698, p = 0.008) but was negatively correlated with parity (95% CI: -0.783--0.315). In addition, lactation time was positively correlated with 305-day milk volume (95% CI: 0.173-0.718, p < 0.004) and peaked at the day of milk production (95% CI: 0.265-0.761) but showed the opposite trend with the milk fat rate (95% CI: -0.633--0.018, p = 0.040) and milk protein rate (95% CI: -0.738--0.215, p = 0.002). Furthermore, milk loss was negatively correlated with peak milk production (95% CI: -0.758--0.258, p = 0.001). Intriguingly, the cost of medications for diarrhea exhibited a downward trend over the past three years. Taken together, these findings confirmed the necessity to reduce the incidence of Mycobacterium avium subsp. paratuberculosis in dairy cows and serve as a guide for the future successful and gradual eradication of paratuberculosis in Chinese dairy cow farms.