2002 Annual Report
Research
Microbial Count in Dolomite Lime and Sand Dairy Bedding
Charles Clanton, Professor
Russ Bey, Professor, Veterinary Pathobiology
Ralph Farnsworth, Professor, Clinical and Population Sciences
Marcia Endres, Assistant Professor, Animal Science
Kevin Janni, Professor and Head
Funding Source
Ag Lime Sales, St. Paul, MN
Objective
The research objective is to compare dolomite lime and sand used as dairy
bedding for environmental microbial count.
Project Description
A 300-cow dairy with east and west freestall buildings was used to compare
the two bedding types. Each building contained a pair of freestalls located
on the west side and a freestall and feed alley located on the east side.
In the pair of freestalls, one side contained added lime and the other
contained added sand. Thus the cow had the choice when walking down the
alley to enter the lime or sand bedded stalls. A total of 12 stalls were
sampled—six of lime and six of sand—on each of three different
collection dates. The same stall was sampled in each of the three collections.
Samples were analyzed for coliforms, environmental strep., and staph.
sp. The three repeated measurements were analyzed for bedding type (lime,
sand), building (east vs. west), location within building (north, middle,
south) and sampling depth (top, bottom).
Results
Comparison of the microbial count of the supply (raw) product to the
counts obtained in the building indicate that the microbes are not being
brought into the system with the purchased lime/sand product. Samples
collected after being used as bedding show an overall increase of 5000-9000
fold.
Bedding type—lime vs. sand—was significantly different and showed
a significant difference in coliforms (p-value=0.0231). There were no
significant differences between bedding types for environmental strep,
staph sp., nor total count.
There was a significant difference between the surface samples and subsurface
samples for coliforms (p-value = 0.0387). There was no significant difference
in depth for environmental strep, staph sp., nor total count.
Results indicate that coliform count in the surface of the lime bedding
was approximately 15 times the coliform count in the surface of the sand
bedding. For the lime bedding, the higher coliform count was in the surface
samples, whereas for the sand bedding, the higher count was in the subsurface
samples. Possible reasons for this pattern might be:
- Liquid (water, urine, milk seepage from udder, etc.) remains on the surface of the tightly packed lime bedding, whereas, in the porous sand, the liquid moves to the subsurface taking the microbes with the liquid movement.
- The finer particles of the lime retain more moisture than the sand, creating favorable conditions for coliform, while sand dries easier.
- The finer particles of the lime have a much larger surface area than the sand, creating more sites for microbes to grow.
- The lime might contain more nutrients for coliform growth not supplied in the bedding environment.
- The increased porous nature of the sand allows more oxygen exchange into the sand, which might lower the coliform count.
- The pH increase due to the lime is not enough to inhibit microbial
growth.
The conclusion is that sand bedding contained lower coliform count than the lime bedding with no difference in environmental strep and staph sp. count between the two bedding types.