Manure isn’t always just manure. It’s often loaded with pathogens that can cause serious illness in livestock and people.
Al Dam, a poultry specialist, said there’s a real risk of spreading disease through manure. Livestock often harbor mycobacteria, Listeria, E. coli, Salmonella and Campylobacter, and these pathogens have the potential to spread to other animals and people via manure.
Swine manure can harbor and may infect other swine with porcine epidemic diarrhea virus (PEDv), African swine fever (ASF) and porcine reproductive and respiratory syndrome (PRRS).
Poultry can carry, become ill and are highly contagious when infected with avian reovirus (ARV), infectious laryngotracheitis (ILT), bronchitis and highly pathogenic avian influenza (HPAI).
When HPAI is known to be present in domestic poultry, birds are depopulated and great care is taken to manage the litter from these birds. However, HPAI is most often transmitted to domestic poultry via droppings from migratory birds including ducks, geese, swans, gulls and cormorants. This seemingly casual transmission results in serious economic loss.
“We’ve also seen HPAI in scavengers or raptors such as hawks, eagles, owls and turkey vultures,” said Dam. “Turkey vultures have died from this. Nothing kills a turkey vulture other than getting hit by a car, but they will die from HPAI.”
Corvids such as crows and ravens have also succumbed to HPAI.
Scavenger mammals including skunks, foxes, coyotes, raccoons, mink and otters have become sick with HPAI from infected dead stock. In Great Britain, a sheep living close to captive poultry was recently diagnosed with HPAI.
Other serious diseases potentially spread by manure include BVD in cattle and Q fever in sheep and goats. All cloven-hooved animals are vulnerable to foot-and-mouth disease (FMD), a potentially serious disease that the U.S. and other FMD-free countries are working to keep out.
Parasites such as Giardia and Cryptosporidium can also be spread in manure. “If you’re accepting manure from a custom applicator, is it from the same species you raise?” said Dam. “That could be a disease risk.”
Dam discussed the potential spread of disease from manure that spills onto roadways. “One gram of infected manure can easily equate to one million dead birds,” he said, referencing the current strains of HPAI. “Is someone running through infected manure on the road? If you’re dropping manure on the road and a feed truck is running by and picks it up then delivers feed to a poultry farm, there’s potential for spread.”
Illness from direct transmission is possible when disease cycles within a poultry flock, but disease can also come from the environment via wild birds, wild animals, insects or humans.
“We can spread disease from wildlife to poultry farms,” said Dam. “We’ve seen that with highly pathogenic avian influenza in operations near waterways – it went from the waterway to the barn then back out to the environment, and many birds were lost.”
For those hauling manure from a farm that has had a disease challenge, composting is one option to minimize the potential of spread. Solid manure can be composted through an aerobic process that creates heat. Properly composting manure at 130º F for over a week will destroy weed seeds and pathogens.
Although tires on manure-handling equipment become heated during travel and are hot enough to kill pathogens, there may be manure on the wheel wells that falls off at the next farm. Dam said this is the reason for cleaning and disinfecting vehicle tires, wheels and undercarriages between farms.
Liquid manure is usually in an anaerobic environment, and Dam said agitation can introduce oxygen to help break down harmful components. However, temperature is critical. A manure tank isn’t heated, so if possible, it’s best to wait for warmer weather to agitate and oxygenate.
In some cases, injection in the field helps reduce pathogen spread. But relying on injection depends on the disease. ASF is a tough virus and will be difficult to manage. Compared to FMD, HPAI is relatively easy to deal with after it’s out of the host because it doesn’t survive in dry or hot conditions.
Properly managed dead stock compost has a lower pathogen risk compared to raw manure. However, depending on location, land application options might be limited.
“Compost must be turned multiple times to reintroduce oxygen to the aerobic process,” said Dam. “There are limits as to how tall the pile or windrow can be, but there are ways to do it to get heat.”
It is possible for a pile can spontaneously combust, so compost temperatures should be monitored.
Many operations have on-farm composting for dead stock, but it’s important that the resulting product is truly compost. Dam said “truly composted” mean the pile has been turned over several times and there are no discernible animal parts visible in any part of the pile.
Curing dead stock compost can be accomplished by allowing the pile to age for several months. If it’s too green when spread, nitrogen is pulled from the soil as the pile continues to compost fully through the anaerobic process. The carbon in shavings or straw pulls nitrogen from the soil as it breaks down.
One popular composting option is windrows, which works well for large birds. “Windrows should be no higher than six feet tall or they won’t chimney properly to get oxygen into the bottom to vent out the top,” said Dam. “It has to be turned.”
He suggested continual flipping of the entire pile in one direction to continue the compost process.
Watch for liquid leachate from composting windrows, which may attract scavengers that remove dead animals from windrows and potentially move them off the farm. This is why rodent management is a critical measure in preventing disease spread.
“If you aren’t managing dead stock properly, you’re inviting these scavengers onto your farm,” said Dam. “You could be bringing disease to the farm.”
