New Options for Reducing Pathogens in Recycled Manure

As dairies got larger and technology became available, dairy producers began developing methods to turn manure into bedding. It seemed like a great opportunity—the product is certainly readily available, and cows need good, quality bedding for their own comfort. Screw presses and other types of separators were purchased to remove water from the manure, and piles of dried manure solids were now prevalent on dairy sites.

Perhaps producers didn’t realize it at the time, but not only were they using a cost-effective source of bedding, by recycling manure into bedding they were also improving their own sustainability footprint.

All of this was good news until they were faced with the reality that bedding with manure solids often puts cows at greater risk for mastitis and high somatic cell counts (SCC).

Ideal environment for pathogens

Although recycled manure solids represent a cost-effective and sustainable bedding source for producers, they also provide an ideal environment for mastitis-causing organisms. When cows lay down, as they do for 10 to 12 hours each day, these bacteria come into contact with the ends of the teats where they can then colonize the teat canal and cause a mastitis infection.

In an effort to characterize the mastitis-causing pathogens in dairy bedding, and ultimately develop an effective strategy to control the outgrowth of these organisms, the ARM & HAMMER Animal & Food Production team collected more than 1,100 bedding samples from dairies across the U.S. Samples were collected from unused piles as well as from the stall, collected at the location of the udder. All types of bedding were sampled, including:

· Green recycled manure solids

· Solids from anaerobic digesters

· Composted manure solids

· Sand

· Other sources, including straw, sawdust, wood shavings and corn stalks

This initial survey sought to quantify and characterize target pathogens, including E.coli and total coliforms, organisms in the Klebsiella group, as well as those in the Group D streptococci group.

As expected, the data clearly showed that pathogen levels increased significantly from the unused bedding pile to the bedding collected from the stall. The next step was to develop an effective solution for controlling this outgrowth. Our goal was to create a safe and effective biological application for reducing the outgrowth of mastitis-causing pathogens in recycled manure solids, and thereby lower the risk of mastitis and high SCC on dairies using manure solids as a source of bedding.

Turned to Bacillus

To find a solution we turned to our existing research on Bacillus organisms and their effectiveness controlling pathogens inside the cow, in silage piles, and more.

Bacillus are beneficial, spore-forming bacteria that can produce a variety of anti-microbial compounds that have an effect on specific pathogens. We evaluated the ability of our proprietary Bacillus strains to inhibit the growth of representative mastitis-causing pathogens isolated from our nationwide survey. Those Bacillus strains with the best inhibition activity were included in a bedding application and tested in on-farm trials.

The farms selected for the initial trials were bedding with green or composted recycled manure solids as bedding and were primarily located in the upper Midwest. Moisture was being removed using a screw press, and our product was applied, as a low volume spray, directly after the screw press. The treated bedding was then applied multiple times per week into deep beds.

Bedding samples were collected from stalls at the location of the udder prior to and after 100 days of product application. Bulk tank SCC and monthly mastitis events from the treatment period were compared to those from the same timeframe in the previous year, allowing us to account for the known seasonality associated with SCC and mastitis.

Lower SCC, fewer mastitis cases

Our initial results demonstrated a substantial reduction in E. coli, coliforms, Klebsiella, and group D streptococci between the pretreatment and treatment periods. Additionally, our bedding application reduced bulk tank SCC counts on all five trial sites by an average of 56,800. Furthermore, four of the five sites observed an average of 9 fewer monthly mastitis events on average.

We later conducted a side-by-side trial on a California dairy where we applied the product directly to bedding in the stalls twice per week. On this farm, we observed a significant drop in SCC among cows in the treated stalls compared to cows in non-treated stalls, along with a 25 percent reduction in mastitis cases and an 8 percent reduction in new infections.

The economic impact of mastitis on a herd can be significant and is well documented. Research shows (Rollin et. al., 2015) that the average cost of a single clinical mastitis case in early lactation is $444. By using a research-proven biological bedding application to reduce pathogen loads in bedding, producers can dramatically improve the health and profitability of their herd by reducing the incidence of mastitis cases and lowering SCC.

Using recycled manure solids as dairy bedding is an economical and environmentally-friendly practice. It becomes an even more viable option for producers when mastitis-causing pathogens in bedding can be safely and effectively controlled, thus reducing their negative impact on the health and well-being of the cow.