Measuring Manure Depth in the PED Era19 November 2014
The Porcine Epidemic Diarrhoea (PED) virus stays viable in stored manure for extended periods of time. In barns that have experienced a PED outbreak, producers should avoid bringing stored manure back up to the surface where it could infect PED-susceptible pigs, according to Jerry May (Extension Educator at Michigan State University, MSU) and Madonna Benjamin (MSU Extension Swine Veterinarian) in 'MSU Pork Quarterly'.
The PED virus continues to impact the US pork industry. Farms that have avoided the virus continue to implement intensive precautions to keep PED out of their herd. Farms that have already experienced the ravages of the virus are taking steps to prevent reinfection.
PED is spread through oral-faecal contact and requires exposure to only a small amount of fecal material to cause infection. Adding to the complications of preventing PED reinfections is the virus’s ability to stay viable in stored manure.
Research conducted by Goyal at the University of Minnesota and reported by the National Pork Board has confirmed that the PED virus may stay viable in manure stored at 40°F (4°C) for more than 28 days. Therefore, stored manure with viable virus, if brought to the floor surface, could reinfect susceptible pigs with PED.
In Michigan, large livestock farms (CAFOs), who are covered under the MI Department of Environmental Quality (M-DEQ) National Pollution Discharge Elimination System (NPDES) permit, are required to monitor and weekly record manure depth in each of the farm’s manure storage structures. In addition all livestock farms, regardless of size, should record the amount of manure removed when spreading manure.
Prior to PED, using a stick to measure manure depth in deep pitted barns, was of small risk to infect pigs with a virus or bacteria. Currently, in this era of PED, there is a risk the small amount of manure brought up on the measuring stick may re-infect the pigs. One option to avoid re-contamination in a barn previously infected with PED, is to “stick and measure” manure depth outside of the barn using the manure pump out ports.
However, there remains the risk of contaminating the periphery of the site and vectors such as personnel or rodents tracking manure virus particles back into the barn and exposing the pigs. As any eight-year-old boy will attest, a better alternative to the stick is a “laser” (Figure 1).
By aiming the laser’s beam down through the slat opening, a laser measure will determine the freeboard between the manure surface and the top of the slats. Dependable laser measures can be purchased for $80.00 to $125.00 either online or at local hardware stores.
A quick field trial using the laser method demonstrated it was easier than the stick and accurate despite the presence of dust and cobwebs.
A laser measure is an excellent device for all sizes of swine farms to use when calculating the manure application rate needed as part of the record keeping requirements when hauling manure. Simply measure the depth of the manure before starting to haul then measure again when done. Once the depth of manure removed is known, it is easy to determine the number of gallons removed and the manure application rate per acre.
To calculate gallons per acre convert all dimension to feet (pit length, pit width and depth of manure removed) then:
- house length × width × depth which equals cubic feet of manure removed
- cubic feet of manure removed × gallons per cubic foot (7.48) = total gallons removed
- total gallons removed ÷ number of acres spread = gallons per acre
Many farms that have experienced PED outbreaks are continuously implementing intensified biosecurity measures to help protect their herd from infection.
Until more is understood concerning the virus’s extended viability, these sites may find it advisable to use precaution and assume viable virus remains in the manure. On these sites it is best to avoid exposing pigs to stored manure as a step to prevent reinfection. In the PED era the “stick and measure” method may be obsolete.
Goyal S. 2014. Environmental stability of PEDv. Pork Checkoff report.