Characterization of clinical mastitis records from one herd in a subtropical environment

Patterns of occurrence and reoccurrence of clinical mastitis, duration of episodes, and number of quarters treated in a large north Florida dairy over 6.5 yr are described. Monthly incidence of milk disposal due to clinical mastitis varied within and between years and ranged from 1.3 to 4.7% of cow-days in milk. In first parity animals, 37.6% of lactations were treated for clinical mastitis, averaging 1.4 episodes per treated lactation. Almost half of these episodes occurred by d 35 of lactation. For second, third, and fourth or greater parities, 35.5, 48.1, and 56.6% of lactations were treated. These lactations averaged 2.1, 2.3, and 2.8 episodes. In parities 2, 3, and greater than or equal to 4, episodes initiated by d 35 of lactation were 28.2, 23.9, and 20.6% of parity episodes. Seventy-two percent of episodes were treated for less than or equal to 7 d. Sixty-seven percent of episodes were treated in one quarter and treatment in two, three, or four quarters accounted for 21.6, 5.5, and 5.9% of all episodes. When two quarters were treated simultaneously, udder halves (front, rear, right, left) were treated more frequently than were diagonals.