Papillomatous digital dermatitis on a commercial dairy farm in Mexicali, Mexico: incidence and effect on reproduction and milk production.

This retrospective study of papillomatous digital dermatitis (PDD) was performed using data for cows that calved between July 1993 and June 1994 on a Mexicali, Mexico, dairy farm in order to calculate incidence rates, and to compare milk yield and reproduction data between affected and nonaffected dairy cows. A total of 190 out of 577 (33%) cows were affected during lactation and six (1%) during the dry period. Fifty-two of 77 (68%) cows that had lesions in the previous lactation and were also present on the farm in the current lactation had lesions in the current lactation. The highest risk for PDD occurred during the first month of lactation (9%). The yearly estimated cumulative incidence risk was 35% and the incidence density rate was 44.6 cases per 1000 cow-months. More animals were affected in summer and fall than in winter and spring. Purchased animals were 3.4 times more likely to be affected than animals born on the farm. Survival analyses indicated healthy cows conceived 93 days after calving (median), but affected cows conceived 113 days after calving (median) (P < 0.01). PDD-affected animals produced less milk than healthy cows, but the difference was not statistically significant in the multiple regression.