Bacteriological evaluation of composted manure solids prepared from anaerobic digested slurry for hygienic recycled bedding materials for dairy cows.

Abstract

Changes in mastitis-causing pathogens, pH and water content in composted manure solids (CMS) prepared from digested slurry were evaluated during turning at 2-day intervals for 8&#xa0;days (C1-C4). The numbers of streptococci, coagulase-negative staphylococci and coliforms were 2.6&#xa0;&#xd7;&#xa0;10, 1.7&#xa0;&#xd7;&#xa0;10and 1.0&#xa0;&#xd7;&#xa0;10&#xa0;colony-forming units (cfu)/g in CMS (C4) (summer), and these counts were markedly lower (P&#xa0;<&#xa0;0.05) than those in CMS (C0 and C1). The bacterial counts ranged from 10to 1.7&#xa0;&#xd7;&#xa0;10&#xa0;cfu/g in CMS (C4) (summer) and were within approved levels, <1&#xa0;&#xd7;&#xa0;10&#xa0;cfu/g, indicating a minimal mastitis risk. The temperatures in CMS (C1-C4) increased to 63&#xb0;C-74&#xb0;C in summer and 67&#xb0;C-70&#xb0;C in winter. The mean pH values in CMS (C0-C4) were 9.2 in summer and 8.7 in winter, and water contents ranged from 61.7% to 69.6% in summer and 73.2% to 66.2% in winter. The significant decrease of pathogenic bacteria in CMS appears to be closely related to temperature >63&#xb0;C for 8&#xa0;days, pH 8.7-9.2, and water content 62% to 73%. This study demonstrates that prepared CMS has value as a recycled material with the potential to alleviate udder health issues in dairy cows.