Data from 37 southern California dairy farms, with an annual average proportion of > 5% of cows affected by papillomatous digital dermatitis (PDD) (cases), were compared with those from 20 dairy farms with ≤ 5% cows affected (controls). Information on dairy environment, management and PDD occurrence was obtained from dairy managers, veterinarians and hooftrimmers, and by direct measurements at the farms. Odds of having a higher proportion (> 5%) of cows affected were about 20 times greater in dairy farms with muddier corrals than in drier dairy farms. Buying replacement heifers was associated with a 4.7-fold increase in the odds of higher PDD prevalence, compared to dairy farms that did not buy heifers. In addition, a positive association was found between risk and number of heifers purchased. Spatial analysis (used to examine distribution patterns of the study dairy farms) showed no evidence of clustering among case or control dairy farms. There was no association between case dairy farms and proximity to the major local river.
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