Influence of digital dermatitis on milk production in dairy cows.
The influence of digital dermatitis as one of the important foot diseases on lameness was studied in its different clinical symptoms in two dairy herds of 193 and 456 cows. Foot disease, on the basis of its clinical symptoms, was classified into 3 types (mild, medium and severe). Average milk yield of the tested cows was 20-30 kg/day and above. Frequency of the disease and its correlations with lactation phase, lactation number and milk yield of cows were studied by regression analysis. The average frequency of disease was 32%, of which 50% could be included in the mild clinical category. The disease was mainly detected in cows in the first phase of their lactation. The frequency of the disease with different clinical symptoms was highest in the first lactation but remained high during the first 3 lactations. Milk yield loss per day was the highest (30-45% between the 100 and 200 days of lactation) in more than 70% of the examined cows - compared with the previous lactations. The frequency of the disease and milk loss in cows with above 8500 kg milk yield per lactation were higher than in cows with lower yield. The frequency of digital dermatitis increased by on exponential curve independent of lactational milk yield. The high frequency of digital dermatitis and production loss caused by the disease reflects the insufficient diagnosis and therapy in large scale dairy populations with high production, especially in the dry period.