Effects of Dairy Manure Management Practices on E. coli Concentration and Diversity

Abstract

Dairy cattle manure has been implicated as a major source of fecal contamination in non-point source agricultural runoff in watersheds. Four different dairy farms in central Texas, each utilizing a different dairy manure management practice, in the Leon River watershed were sampled for E. coli using EPA Method 1603, with a percentage of isolates genotyped and phylotyped using the Clermont quadruplex PCR method. E. coli concentration was reduced as manure moved through the management process with tiered management systems lowering concentration the most. E. coli genotypes showed no correlation with sampling season or management practice. The highest percentage of unique genotypes was observed in dairy 2, which consisted of a settling basin then lagoon. One genotype was seen across all dairies and composed 15% of all genotypes characterized. E. coli phylotypes showed no seasonal or management practice trend. B1 was the most common phylotype isolated from all dairies and time periods, which was expected. Potentially pathogenic phylotypes were rarely observed, which could indicate isolation from pathogenic E. coli introduction. Dairy manure management practices that separate solid from liquid waste reduced E. coli concentrations the most based on these results.