Investigation of the relationship between method of processing and bacteria counts in ready-to-use recycled manure solids bedding on Midwest dairy farms

Abstract

There has been a rapid increase in adoption of recycled manure solids (RMS) as bedding in Midwest dairy herds over the past 10 to 15 years due to perceived advantages such as cost and availability. However, several studies have reported increased bedding bacteria counts (BBC) and increased mastitis risk in herds using RMS as compared to inorganic or organic non-manure materials. Although many RMS dairies use either green/raw (GRN) solids or solids first processed through an anaerobic methane digester (DIG), some herds have adopted mechanical composters (COM) or dryers (DRY) in an effort to lower BBC and control mastitis. Research is needed to evaluate potential benefits and costs of adopting these technologies. This research team initiated a study to evaluate udder health, air quality, antimicrobial resistance in solids, and economics, for herds using different RMS processing methods. In a companion abstract, we determined that use of COM or DRY was associated with improved udder health and milk production as compared to GRN. In this abstract, we explore if these benefits are likely to be explained by differences in bedding characteristics, such as BBC, for the 4 processing systems investigated. The objective of this portion of the study is to investigate if method of processing RMS is associated with BBC in ready-to-use (RTU) RMS on Midwest dairy farms.