Health, Environmental Health, and Hog Manure
A - A Soil Macro-what?
You have heard by now of soil macropores
- those cracks, openings, continuous pores in the soil that help aerate and
drain the soil. They also can provide a direct link between the soil surface
and tile drains. Unfortunately liquid manure can follow this pathway, under
certain conditions, and contaminate surface water. Ten years of Ontario research
looking at this problem has told us:
1. Macropores exist - By blowing smoke into tile drains, it is very apparent
that there are connections to the surface. Smoke puffs out of the ground over
2. Liquid manure can travel through macropores and enter tile drains -We aren't
talking about a large volume compared to the total applied to the land, but
even a small amount can cause damage to some streams, depending on stream flow.
Ammonium, bacteria, and organic matter are the culprits.
3. Macropore flow occurs within 24 hours of spreading (or after a rainfall)
- The studies have shown that manure can be found running out of drains within
20 minutes of spreading. If there has been no flow by the time 24 hours has
elapsed, there likely won't be any, unless there is a heavy rainfall quite soon.
4. If the drains aren't running there is no problem - This sounds obvious, but
it may be a spreading strategy for some farmers.
5. If the soil has been worked recently, no problem - The most effective way
to prevent flow to tile drains is to till the soil before spreading manure.
It doesn't seem to take much to break up the macropores (pathways) at the soil
6. Plugging drains works for some people - This involves plugging the drain
outlets at spreading time and leaving them plugged for at least a week. We have
found that you can get a considerable reduction in the ammonium and bacteria
by holding the water in the tile system. The only trouble is, you need fairly
flat land so that you don't create too much pressure in the drain system, forcing
water up to the surface at locations other than the outlet. Also, if it rains
within the week, and there is still field work remaining, the soil may not dry
out fast enough with the system plugged. The practice of plugging drains has
rather limited usefulness.
7. Monitor tile drains during and after spreading - While this isn't a pollution
prevention strategy, it at least keeps you on top of the situation. It is possible
that you have never had this problem and never will, but keeping an eye on the
outlet is good insurance. It is quite easy to tell if you have a problem - the
odour and colour are unmistakable.
B - Cryptosporidium and Pigs
We are running a study that is looking
at a relatively recent problem, but one that is getting a lot of attention -
crytosporidium in drinking water. Since we are just now compiling laboratory
results, we do not have much hard data, but a background understanding would
is a protozoan, a single-celled parasite, that lives in the intestines of animals
and people. This microscopic pathogen causes a disease called cryptosporidiosis.
The dormant (inactive) form of Cryptosporidium, called an oocyst (O-o-sist),
is excreted in the feces (stool) of infected humans and animals. The tough-walled
oocysts survive under a wide range of environmental conditions.
You can get infected with Cryptosporidium
when you put anything in your mouth that has been in contact with feces from
an infected animal or person. Cryptosporidiosis can be easily spread among people
in close social groups such as families, day care centers, and nursing homes.
People who work with animals, especially young animals or animals with diarrhea,
have greater chance of exposure to the parasite. You can also get cryptosporidiosis
by drinking water or eating food that has been contaminated with oocysts.
Oocysts are not killed by typical household disinfectants, including bleach,
but are killed at temperatures over 160 F. Thorough drying in a clothes dryer
will kill oocysts by desiccating them.
Cryptosporidiosis has long been a problem
in young farm animals, such as calves. Cryptosporidium was first recognized
as a cause of human disease in 1976 but was rarely reported in humans until
1982. There have been major outbreaks in several US cities (eg. Milwaukee) and
in Canadian communities (eg Collingwood, spring 1996).
Is it runoff from fields receiving manure
that is the problem? Or is the source of crypto in surface water septic system
effluent reaching surface water, or sewage treatment plant discharge, or runoff
from fields receiving sewage sludge, or simply wildlife? Our study aims to find
answers for at least part of this question.
1. To investigate the prevalence of Cryptosporidium
parvum in typical livestock manure storages and in sewage sludge in Southwestern
2. To compare the prevalence of C. parvum in tile drainage discharge water from
2 different areas - those having a high concentration of livestock in the drainage
basin, and those having no livestock in the drainage basin.