Investigation of the relationship between manure processing method and levels of mastitis pathogens in recycled manure solids bedding on Midwest dairy farms

Abstract

While many dairies use green (GRN) recycled manure solids (RMS) bedding, some first process slurry through an anaerobic digester (DIG), while others have adopted secondary (SEC) pro­cessing methods such as mechanical composters (COM), hot air dryers (DRY) or, more recently, infrared drying (IR), in an effort to lower mastitis pathogen counts in ready to use (RTU) solids. A previous study reported that Midwest herds using DIG as the sole processing method had lower levels of coliforms and Kleb­siella spp. (Kleb), but no reduction in streptococci or strep-like organisms (SSLO) in RTU solids, and no improvement in ud­der health, as compared to herds using GRN RMS. In contrast, herds using COM or DRY RMS bedding had lower bacteria levels and improved udder health as compared to herds using GRN solids. However, the latter study included a limited number of herds using DIG RMS. The objective of this observational study was to investigate the relationship between use of DIG and other SEC processing methods and levels mastitis pathogens in RTU RMS, as well as bulk tank (BT) SCC, when compared to herds using GRN RMS bedding.