Methods of processing recycled manure solids bedding on Midwest dairy farms II: Relationships between bedding characteristics and bedding bacterial count

The first objective of this study was to identify bedding characteristics associated with bedding bacterial count (BBC) in ready-to-use (RTU) recycled manure solids (RMS). The second objective was to explore the association between processing method and bedding characteristics in RTU solids. A third objective was to investigate factors associated with BBC in used solids (after placed in stalls). This observational study recruited 29 premises in Minnesota and Wisconsin. Farms were visited twice, once in August of 2019 and again in January of 2020. At each visit, the herd manager/owner completed a questionnaire describing facilities, bedding and manure management, and mastitis control practices. Additionally, pre-processed RTU and used bedding samples were collected for determination of BBC (coliforms, Klebsiella spp., Streptococcus or Streptococcus-like organisms and Staphylococcus spp.) and bedding characteristics (dry matter [DM]), organic matter [OM], water soluble carbohydrates, total nitrogen, soluble nitrogen and pH). Mixed linear regression showed that increased DM, decreased OM and RMS processing method were all associated with reduced BBC in RTU RMS samples. Processing method for RMS was associated with DM, total nitrogen and soluble nitrogen, but not other characteristics in RTU RMS samples. Low BBC in RTU solids, decreased OM in RTU solids, and use of deep bedding systems were associated with lower BBC in used RMS. Implications for these findings are that producers should strive to put clean and high DM fresh (RTU) bedding into stalls. Monitoring BBC and DM in RTU solids may be of value for producers using RMS bedding.