Variations in the Physical Properties and Microbial Community of Dairy Cow Manure—Implications for Testing and Efficacy of Footbathing Products

SIMPLE SUMMARY: Digital dermatitis is a major welfare problem for dairy cows, causing lameness and pain. It is infectious and caused by bacteria; therefore, walking cows through footbaths filled with disinfectant is a common part of control programmes. As the cows walk through the footbaths they can defecate, contaminating the disinfectant with organic matter and bacteria, which can reduce the disinfectant performance. The properties of manure (including pH, dry matter and bacterial community composition) might impact how manure contamination affects disinfectant performance. These properties might vary depending on the production system (including diet) of the animal. This study investigated the physical properties and bacterial composition of dairy cow manure from two production systems and examined whether the source of contaminating manure impacted the efficacy of footbathing disinfectants. Differences in dry matter content and bacterial community composition were found between manure samples from different production systems. When manure was added to three disinfectant products, the source of the manure affected the performance of two of the products. The source of manure used in testing products could therefore affect how well products perform. Some products might perform better on one farm than another, depending on the properties of the manure that contaminates footbaths. ABSTRACT: Footbaths containing disinfectants are used on dairy farms to reduce the spread of digital dermatitis; however, they commonly become contaminated with manure. This trial investigated the physical properties and microbial composition of dairy cow manure from two production systems and examined whether the source of manure impacted the efficacy of footbathing disinfectants. Manure was collected from eighteen dairy cows, nine housed and fed grass silage (HOUSED) and nine at pasture (PASTURE). The pH and dry matter content was determined, total DNA was extracted and the region v3-v4 of the 16s rRNA gene sequenced. The efficacy of formalin and two trial products (TP1: peracetic acid and hydrogen peroxide; TP2: chlorocresol and triamine) was evaluated when mixed with manure from the two production systems. Production system differences were found in manure dry matter content, bacterial microbiome and the efficacy of both trial footbathing products but not formalin. The properties of manure affected the results of laboratory testing and therefore have the potential to influence footbathing disinfectant efficacy when footbaths are contaminated with manure. Further research into the impact of organic contaminants on the efficacy of disinfectants could facilitate the development of improved testing programmes and disinfectant products.