Evaluate Your 'Hygiene' Risk for Environmental Mastitis
Environmental bacteria, including the Environmental Streptococci and
Coliforms, cause most new mastitis cases on dairies. New infections are
mainly related to the number of bacteria located at the entrance to the
teat end at any point in time. In fact, many studies have shown that
clean cows and housing are keys for low herd bulk tank somatic cell
counts. Herds with lowest new infection rates often have the cleanest
cows and clean comfortable beds for the cows.
Several
tools are available to communicate level of mastitis risk from the
cow’s environment. These tools if used routinely can alert you to the
need for rapid changes and can provide a way to monitor and record
impact of improvements made. All tools are quick to use and can help to
pinpoint the major environmental factors leading to higher than desired
herd somatic cell count and clinical mastitis rates. Tools described
below can identify risk for environmental bacteria and include hygiene
scoring chart, the teat end cleanliness scorecard, and bedding
cultures. Presence of manure and contamination of bedding are important
risk factors for environmental mastitis. The more manure, especially on
the rear legs and udder, the greater the risk of a new mastitis
infections. Hygiene scorecards have been developed to provide a
subjective but consistent method to evaluate cow cleanliness on-farm.
The hygiene scorecard developed at University of Wisconsin (Figure 1),
scores cows based on the major methods by which manure is transferred
to the udder. The scorecard allows you to monitor degree of cow
cleanliness and to identify the major sources of manure. Manure
transfer methods used in the scorecard are:
1. Direct Transfer -> Cows lie down in a manure contaminated stall or bedded area and bacteria are transferred directly to the udder
2. Leg Transfer
-> Cows walk through manure, coating their feet and legs. Bacteria
are transferred to the teat ends when the cow lies down and when the
udder rests on the hind feet
3. Splash Transfer -> Cows walking through walkway or alley liquid/manure splash manure toward the udder
4. Tail Transfer -> The tail becomes contaminated with manure and transfers bacteria to the rear udder and flank
The importance of each transfer method varies with housing type. For
example, cows housed in a freestall with flush alley cleaning will
likely be exposed to bacteria from all four manure transfer methods.
Cows housed in a tie-stall with limited outdoor exposure time will
likely be at greatest risk from direct transfer of bacteria to the teat
ends. Degree of exposure within any housing system will vary with herd
management. All cows in herds with less than 100 cows should be scored,
whereas at least 25 percent of cows in each group should be scored in
herds with more than 100 cows. Legs, udders, and flank and upper legs
are the most important sites from which bacteria are transferred to the
teat ends. Each site on a cow is scored from 1 to 4, with a 1 meaning
the site has little to no contamination and a 4 meaning the site has
the worst risk for manure contamination and chance for new mastitis.
Greater detail on use of the scorecard can be found at the web sites
listed below or by calling your county Penn State Cooperative Extension
dairy educator.
The teat cleanliness scorecard can be used
to evaluate risk of new mastitis right before the milking unit is
attached. An example developed by WestfaliaSurge can be found at
http://www.westfalia.com/Images2005 percent20Engel percent20NMC
percent20Mtg percent20Poster_tcm83-19406.pdf This tool is simple to use
and is a very visual way to record and communicate the risk of new
mastitis cases to milkers. Time spent cleaning teat ends during the
prep procedure will reduce the chance that bacteria will enter the
udder during milking and cause environmental mastitis. A high
percentage of 3 and 4 scores indicates that further time and attention
should be spent cleaning teat ends before attaching the milking unit.
Bedding
cultures to identify bacterial contamination in fresh and used bedding
are another tool to communicate the impact of time spent maintaining
stalls on mastitis risk. Bedding samples should be collected using
clean nitrile gloves from 6 to 8 spots in the fresh bedding and should
be placed into a gallon ziplock bag. The sample should be mixed and a
smaller subsample put into a quart ziplock bag to be analyzed. The
fresh or unused bedding sample provides a baseline level of bacteria
that can be compared with ‘used’ bedding samples. In some cases,
results may show that the fresh bedding is actually contaminated with
high levels of bacteria before being put into stalls. Bedding should
also be collected from stalls after a day or several days of use.
Again, bedding should be collected from several spots and from several
stalls. The sample should be mixed and subsampled. The subsample should
be placed into a quart ziplock bag. Bedding samples should be frozen
and sent overnight to an experienced laboratory.
Some
studies suggest that total bacteria in used bedding samples should not
be greater than 1-million colony forming units per ml (CFU/ml).
However, this is a rough estimate. Fewer Coliform bacteria need to be
present in the cow’s environment to cause a new infection compared to
Environmental Streptococci. More recent research suggests that keeping
Environmental Streptococci levels below 1-million CFU/ml level may be
suitable to prevent most new infections, however, a level less than
20,000 CFU/ml may be important for E. coli and especially for
Klebsiella bacteria in order to prevent most new infections.
Regardless, low levels of bacteria in the bedding are important to
keeping environmental mastitis risk to a minimum.
Many
additional tools are available for monitoring environmental and
contagious risk for mastitis on your dairy. Tools should be used on a
routine basis. Fine-tuned maintenance of the environment will be more
critical for cows at dry-off and around calving and during times of
heat stress or rainy weather. Shedding rates for Coliform bacteria
appear to be increased during summer and bacteria grow more rapidly
during the summer, increasing mastitis risk. Because of this, bedding
maintenance may need to take place more often and be more thorough
during periods of increased risk. Environmental mastitis risk tools can
be helpful when troubleshooting herd somatic cell count and or high
rates of clinical mastitis and for communicating the impact of quality
or substandard work on the dairy.
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Sandy Costello, Extension Educator - Dairy Herd Health, Penn State Cooperative Extension, Cumberland County
Web Sites:
University of Wisconsin-Madison Veterinary School Hygiene Color
Score Card: http://www.vetmed.wisc.edu/
dms/fapm/fapmtools/4hygiene/hygiene.pdf
Hygiene Scoring Form: http://www.vetmed.wisc.edu/dms/fapm/fapmtools/4hygiene/hyscorefrm.pdf Hygiene
Scoring Summary: http://www.vetmed.wisc.edu/dms/fapm/fapmtools/4hygiene/hyscoresum.pdf
