SURVIVAL OF FECAL BACTERIA IN DAIRY COW MANURE
Transactions of the ASAE , 47 , 2004
Wang, L., Mankin, K.R., Marchin, G.L.
Bacterial pollution of water is impacted to a great extent by the ability of bacteria to survive in manure following excretion. We investigated the effects of environmental temperature (4°C, 27°C, and 41°C) and manure moisture content (30%, 55%, and 83%) on the survival and release of indicator bacteria in dairy cow manure. Fresh manure samples of about 60 g were packed to 12 mm depth in polystyrene dishes and held at controlled temperatures and moisture contents for up to 103 days. Supernatant from a distilled−water extraction was enumerated for fecal bacteria (fecal coliforms, Escherichia coli, and fecal streptococci) by the membrane filtration method. Bacterial populations increased as much as 2.5 log10 (over 300×) in the three days following excretion. Temperature had a significant overall effect on survival of all three fecal bacteria, whereas moisture content produced a consistent effect on fecal streptococci survival only. Fecal streptococci showed no significant die−off at any temperature or moisture content studied. In contrast, no measurable E. coli or fecal coliforms were found in supernatant water samples from the 41°C treatment after day 35. E. coli and fecal coliform populations for the 4°C treatment at lower moisture content (30% and 55%) conditions were close to the detection limits after five weeks, but significant numbers of E. coli (2.34 × 104 cfu g−1 wet manure) and fecal coliforms (3.84 × 104 cfu g−1 wet manure) remained for the 4°C treatment at 83% moisture content after 103 days. First−order die−off rate coefficients for E. coli were found to be appropriate after day 3 for about a 3−week period and averaged 0.11 d−1 at 4°C, 0.20 d−1 at 27°C, and 0.32 d−1 at 41°C. Results from this study suggest that barnyard, feedlot, and manure management practices that detain manure at higher temperatures (e.g., 41°C) will decrease the E. coli and fecal coliform populations but not those of fecal streptococci. Coliform bacterial populations tested remained viable for long periods (>3 months) particularly at moderate temperature (27°C) for any moisture level, and streptococci survived under all conditions studied.