Histograms showing the number of occurrences of the 47 OTUs distinguished in DGGE profiles obtained from the complete set of PCR-positive dairy farm samples. Number of PCR-positive samples for each series: soil samples, 24; forage samples, 21; feed samples, 53 (including 22 grass silage, 14 maize silage, and 17 dry hay samples); raw milk samples, 66.