Microbiological Quality and Pathogen Persistence in Probiotic Amended Recycled Sand Bedding in Dairy Barns

Introduction: Sand bedding in dairy operations offers the advantages of increased milk yield, improved animal welfare and higher hygienic standards compared to other bedding types (e.g., straw). However, waste management represents a key challenge with sand bedding; it cannot be spread onto land or composted. Sand bedding disposal can cost a small dairy farmer over $10, 000 in waste management, hence there is interest in recycling to reduce the financial burden. Although recycling can reduce the amount of sand required to be disposed of there is the risk of pathogen accumulation that can negatively affect herd health. 

Purpose: The focus of the current work is to determine the sanitary quality of recycled sand within commercial dairy farms and how pathogen persistence can be reduced in the presence of a Bacillus probiotic preparation. 

Methods: Sampling and testing of virgin and recycled sand occurred every 6 weeks from May to December. A 35 day microcosm setting was used to determine the impact a Bacillus probiotic had on bacteria of interest.

Results: Results to date have established that the microbiological quality of sand deteriorates over time with the accumulation of enteric bacteria. Over a summer season the average values of E. coli levels recovered on recycled sand samples taken from the barns was 4.3 log CFU/g that was significantly higher compared to virgin sand (<2 log CFU/g). Recycled sand harbored coliforms (6.3 log CFU/g), Bacillus spp (5.3 log CFU/g) and a total aerobic count of 7.8 log CFU/g both of which were significantly higher than fresh sand. Laboratory-based trials have illustrated that inclusion of Bacillus probiotic within sand bedding can significantly decrease the persistence of E. coli. 

Significance: The research is of direct significance to dairy farmers considering implementing recycled sand bedding and in broader terms, by reducing pathogen prevalence as part of a One Health approach.