Economic impact of clinical and subclinical mastitis: a herd-level cost analysis in dairy cattle farms of Lugo (Northwest of Spain).

Mastitis remains one of the most important causes of economic loss in dairy farms. However, few studies have quantified the herd-level costs of both clinical (CM) and subclinical (SM) mastitis. The objectives of this study were to estimate the annual economic impact of CM and SM in dairy farms located in Northwest Spain, to disaggregate costs into their principal direct and indirect components, and to assess the relative contribution of both presentations of mastitis to total economic losses. A retrospective observational herd-level economic analysis was conducted using production, health, reproductive, and economic data collected during 2023 from 63 commercial dairy farms enrolled in a milk recording and quality control program. A deterministic economic model integrating farm-specific data with coefficients derived from the literature was used to estimate direct and indirect costs. Parameter uncertainty was evaluated through a Monte Carlo simulation with 10,000 iterations and a dominance analysis. Average mastitis total cost was €31,643.48 per farm per year (€261.23/cow). Subclinical mastitis accounted for €18,480.56 (58.4%) and CM for €13,162.99 (41.6%). In the deterministic analysis, milk production losses were the largest contributor to both CM (€3679.60 ± 5954.92) and SM (€15,643.70 ± 14,797.20) costs. However, under uncertainty, culling-related costs were the most frequent primary driver of total economic losses (72.2% of simulations), followed by increased days open (21.9%) and milk-related losses (5.9%). Mastitis represents a substantial economic burden in Atlantic dairy systems. Although milk losses are consistently important, culling and reproductive inefficiency may dominate total costs under plausible biological and economic conditions.