A mathematícal model for assesing the effect of mastitis in daíry cattle Is proposed. Dp = Po   n  ∑   Kej  x  Cjj=1    - Po  Dp = losses in milk production due to mastitisPo = observed milk productionC  = Quarter proportion for each inflammation gradeKe = Proportional production (constant) for each inflammation gradePO∑KexC = Potential milk production Se propone un modelo matemático para es­timar pérdidas atribuidas a la mastitis del bovi­no productor de leche.