Apr. 08
Treatment of Subclinical Mastitis
Pamela L. Ruegg, DVM, MPVM
Take home message:
- It is possible to achieve satisfactory cure rates using intramammary antibiotics for treatment of subclinical mastitis during the lactation period but the cost effectiveness of the treatments will vary depending on herd & cow specific factors
- Treatment of subclinical mastitis during lactation is not generally cost effective for herds that are able to effectively reduce transmission of contagious pathogens unless there is an alternative use of the milk that would be discarded
- If treatment is undertaken, cow specific risk factors should be considered to identify cows that are most likely to respond to treatment
Mastitis occurs in both a clinical and subclinical form. Clinical mastitis is readily apparent and treatment decisions for it are generally motivated by a desire to return milk to a saleable state. Detection of subclinical mastitis is more difficult and the use of indirect tests (such as counting somatic cells or bacteriological analysis of milk samples) is necessary. Subclinical mastitis is often undetected and therefore has the greatest economic impact.
With the exception of infections caused by Streptococcus agalactiae, treatment of cows diagnosed with subclinical mastitis is usually discouraged because discard of saleable milk results in financial loss. However, there are negative outcomes that result from having cows affected with subclinical mastitis in the dairy herd and many progressive dairy managers are interested in determining the impact of treatment. The potential benefit of treatment is especially relevant for herds that use pasteurizers and feed waste milk to calves.
Several recent studies have evaluated the impact of treatment of subclinical mastitis and all have confirmed that the most important step is to first identify the type of pathogen that is most frequently associated with subclinical cases on the individual farm. The only way to definitively identify mastitis pathogens is to collect aseptic milk samples for microbiological examination. Recent research has also reinforced the importance of focusing first on reducing transmission of mastitis as the long term impact of treatment will only be effective if prevention is effective. Finally, treatment is only effective for cows with specific characteristics and therefore treatment of subclinical mastitis should be targeted based on specific characteristics of cows, pathogens and individual herds. Read the full article here.
Mar. 07
Developing a Biosecurity Plan to Prevent Introduction
of Mastitis Pathogens
Article Summary:
- Biosecurity addresses prevention of introduction of pathogens
and prevention of spread of pathogens
- Highest risk of introduction is from addition of heifers or cows
- Certain practices can help reduce the risk of introduction of pathogens
A biosecurity plan has two aspects; the
prevention of introduction of contagious pathogens to the dairy and the
prevention of spread of either contagious or environmental pathogens
on the premises.
We’ll consider the prevention of
introduction of a contagious pathogen to a dairy first. The contagious
pathogens are Streptococcus agalactia, Staphylococcus aureus, and Mycoplasma
and they are so named because they are well adapted to survive in the
cow, and can easily spread from one animal to another especially during
milking.
The highest risk of introduction is from the addition of heifers
or cows to the dairy and the older the animal added, the higher the risk.
It seems important to notice that we refer to reducing the level of risk
not the elimination of risk because these bacteria are not shed continuously.
Let’s consider some steps and information that helps us quantify
risks even if it is referenced by the vague term of reduction of risk:
- Obtain knowledge about the
herd of origin by reviewing previous bulk tank cultures and
individual cow cultures. Factor-in that the greater the number
of negative sample available the more assurance there is that
the contagious pathogen is not on the sellers’ dairy
- Culture the individual animal
upon arrival to the dairy; just remember that contagious pathogens
are sporadic shedders
- Isolate purchased animals to prevent
spread until you are totally assured that the incoming animals are
uninfected
- Maintain a regular surveillance
of the bulk tank, individual clinical cases, and the subclinical
population of cows for contagious pathogens by culturing in order
to continue monitoring for these three
- If animals have contact with animals
from other herds at public exhibitions or commingled raising and
then returning them to your own herd treat them as purchased animals
- Develop a plan for visitors to
your dairy that addresses their outer ware and past exposure to livestock
Feb.
07
Managing Milk Quality is Managing People
Article Summary:
- Barriers to improvement of milk quality are often related to
motivation and implementation rather than lack of technical knowledge
or skills
- Implementation of management practices is dependent on the
ability to clearly communicate with farm personnel
Improving milk quality often consists of managing a complex system
that includes people, cows, machines and the environment. Surveys
of veterinarians and other professionals working with dairy producers
indicate that barriers to improvement of milk quality are primarily
related to motivation and implementation rather than lack of technical
knowledge or skills.
In a survey of 165 Wisconsin dairy professionals the existence
of too many other problems (55%) and few incentives for production
of high quality milk (48%) were the predominant reasons cited for
failure of farms to improve milk quality (Rodrigues and Ruegg,
2004). Only a few responders indicated that they felt the need
for additional on farm training programs (24%).
During the summer of 2006, farmers (n = 140 responders) that had
completed the Milk
Money program were asked an open ended question that stated: “What
is your greatest challenge in maintaining production of high quality
milk?” The most common responses were related to employee
management (mentioned by 26% of responders) followed by management
of the environment of the cow (mentioned by 14% of responders) and
maintaining consistency in the milking process (mentioned by 11%
of responders) (Hohmann
and Ruegg, 2007, NMC proceedings).
It is no mystery why employee management is mentioned so often
because 51% of farms responding to a post Milk Money survey,
indicated that they employed Spanish speaking employees, yet
only 15% indicated that they had any ability to speak or understand
Spanish and 40% had never employed an interpreter.
These communication challenges are a fundamental reason why
producing high quality milk continues to be a challenge for many
farms. The ability to implement recommended management practices
is an essential aspect of quality milk production. Implementation
is dependent on the ability to clearly communicate the value
of these practices and to motivate farm personnel to consistently
apply them.
Jan.
07
Occurrence & Management of Clinical Mastitis on Organic
Dairy Farms
Article Summary:
- Conventional farmers reported a greater occurrence of clinical
mastitis than Organic farmers
- Treatment practices vary dramatically between conventional
and organic herds
- Perception of cure after treatment was not significantly associated
with farm type
Clinical mastitis occurs on virtually all dairy farms
regardless of management system but the perception of mastitis
varies greatly from farm to farm.
In a recent study, we found that organic farmers
reported & treated less cases of mastitis as compared to conventional
dairy farmers (Pol M, and P. L. Ruegg. 2007. "Treatment practices
and quantification of antimicrobial usage in conventional and organic
dairy farms in Wisconsin". J Dairy Sci 90:249-261).
Conventional farmers reported an occurrence of 41
cases of clinical mastitis per 100 cows/ year while organic farmers
reported 21 cases per 100 cows/year.
While these differences appear large, part of the
difference probably occurs because of differences in detection
rather than differences in occurrence of mastitis. In our study,
detection of clinical mastitis and criteria used to decide if a
cow was cured after treatment for clinical mastitis were significantly
associated with farm type. Ninety percent of conventional farmers
reported that they identified mastitis based on observation of
milk in contrast to only 45% of organic farmers. Likewise, the
assessment of cure after treatment for clinical mastitis was based
on observation of normal milk for 75% and 20% of conventional and
organic herds, respectively.
Treatment practices for clinical mastitis varied
dramatically between conventional and organic herds.
All conventional farmers enrolled in our study used
intramammary antibiotics to treat clinical mastitis. Most organic
farmers reported the use of organic products for treatment of clinical
mastitis but none reported the use of antimicrobials for this purpose.
Bovine whey products were the most common treatments used by organic
farmers but other products commonly used were garlic tincture,
aloe vera, and vitamin C.
While treatments were different, the perception of
cure after a treatment of clinical mastitis was not significantly
associated with farm type. About half of conventional farmers,
and one third of organic farmers estimated that less than half
of the treated clinical cases of mastitis were cured as a result
of treatment. Almost 74% of organic farmers using compounds to
treat clinical mastitis were satisfied or very satisfied, while
only 40% of conventional farmers were satisfied or very satisfied
with the products used.
For both herd types, the overall proportion of animals
culled due to mastitis was about 8.8%.
Sept.-Oct. 06
Management of Mastitis on Organic Farms
There is a pervasive myth that milk quality of organic dairy farms is considerably less than milk quality on conventional dairy
farms but the data does not support that belief. While most herds of all types and sizes produce high quality milk, when viewed on
a population level, smaller dairy herds of all farm types tend to be overrepresented in higher categories of bulk tank SCC (BTSCC)
(Rodrigues et al., 2005 J Dairy Science). Similar to smaller conventional herds, organic dairy herds tended to have slightly
higher BTSCC (Zwald et al., 2004 J Dairy Science) and have a slightly higher prevalence of recovery of contagious mastitis
pathogens (Pol and Ruegg, 2006 J Dairy Science, in press).
Differing management strategies are used at dry off for conventional and organic herds. In a study of 20 organic and 20
conventional dairy herds in Wisconsin, organic farms used an intermittent milking technique to dry cows off more frequently
than conventional herds (Pol and Ruegg, 2006, JDS in press). The use of intramammary dry cow therapy is highly adopted by
conventional dairy farmers but is not allowed for organic dairy farmers.
In our study, about half of organic farmers reported that they used a variety of non-antimicrobial products to improve udder
health at dry-off. Ultra filtered bovine whey products were the most commonly administered dry cow treatment. Other products
used by organic farmers included vitamin supplements, microbial supplements, aloe vera, homeopathy, vegetables oils and vitamin C.
While there is no peer reviewed data that suggests that these products are efficacious, our recent work suggests that both
conventional and organic farmers had similar appraisal of products used for dry cow therapy. Overall, about 80% of both organic
and conventional farmers reported that they were satisfied or very satisfied with the result of the dry cow treatments.
Next month, we will review our data on products used to treat clinical mastitis in organic dairy herds.
Top of Page...>
Aug 06
Bulk Tank Math and Monitoring Decisions
Most farms have some sort of a goal for bulk tank SCC (BTSCC). Interestingly, having this goal seldom stimulates a need to
understand the math behind the current BTSCC. Each cow contributes a proportion of the cells and the milk in the tank. An
individual cows’ proportion of the BTSCC is considered to be her cell contribution (her SCC times her production) / the total
cells in the tank (sum of all contribution). While this mathematical approximation of the BTSCC is not exact for test day
(because some cows may not be in the tank or errors have occurred in either measuring production or in the laboratory)
it is a useful evaluation. Many computerized management programs and DHIA reports include a list that describes the percent
of SCC contributed to the bulk tank by individual cows.
By itself this report is just an example of the ease with which computers can do math. To make it valuable we need to answer some
important questions about herd dynamics:
Do a few high producing cows contribute much of the BTSCC?
Are chronic cows contributing regularly?
Do a high proportion of the cows contribute some somatic cells?
An understanding of the math allows us to decide if management actions will impact the BTSCC. An example is deciding between
culling chronic cows or improving the environment. If environment is the issue, culling would be positive in the short term but
neutral in the long term. Improving the environment would be neutral in the short term and positive in the long term after the
chronic cows had been culled only if newly infected cows hadn’t taken their place.
In addition to having proper expectations it is important to decide how the effect of an action will be measured. BTSCC is very
easy to monitor but it is seldom the measure of choice for a specific action. Monitoring the new infection rate and having a
SCC herd plan that assesses who, where, and when animals become infected would be far better.
Top of Page...>
July 06
Practical Biosecurity
Transmission of infectious disease occurs when uninfected
cows come in
contact with infected cows or manure, milk, blood or tissue that
originated from infected cows. Based on a recently published survey
of
Wisconsin dairy herds, we know that several very risky animal
management practices commonly occur on Wisconsin dairy farms.
Surveyed farms indicated that 77% of farms house sick cows in
calving
pens, 44% of farms have purchased cattle in the last 3 years and
62%
of those bought the highest risk animal (a lactating dairy cow).
Farmers also indicated that very little information is known about
the
source herd of most purchased cattle and very little testing is
performed on purchased cattle.
To minimize the risk of spreading infectious disease with purchased
cows, we recommend that farms "Practice Safe
Purchasing" by applying the following principles:
Buy younger cattle that have had less opportunity to become infected,
avoid purchase of commingled animals, minimize relocation stress
by
moving animals in groups, keeping herdmates together, and keeping
age
groups separate.
Determine the status of: Johne's disease, heel warts, abortion,
respiratory disease, and mastitis on the source herd.
Request results of a recent bulk tank culture, do not buy cattle
with
unknown histories, do testing as advised by your veterinarian
Contagious mastitis (such as Staph aureus and Mycoplasma) can
be
transmitted when teats of uninfected cows come in contact with
milk
from subclinically infected cows. To reduce the risk of such
infection: keep sick cows separate from healthy cows, milk sick
cows
with different equipment than equipment used to milk fresh or healthy
cows, do not use multi-dose intramammary treatment vials.
Top of Page...>
May 06
Useful resources
When we find resources we regard as helpful to the
dairy business community, we like to make sure as many of you are
made aware of them as possible. That's the case this month with
two web sites we'd like to point out.
We direct you first to he "Agriculture Labor Management" page
hosted by University of
Vermont Extension. The site is a great
resource for topics such as: Employee Recruitment, Compensation,
Personnel Policies, Supervision and Management, Training, Safety,
The Multicultural Workforce, and Legal and Compliance Issues.
There are real-world examples found in the section and great references.
You'll finds tips and advice from a variety of sources and enough
detail to help you sort through many employee management issues.
Our second featured web site is the "Additional Resources" page
found on the web site of the College of Veterinary Medicine, The
Ohio State University Extension. First on the page is a PDF document
titled: A Young Person's Guide to Keeping Animals Safe and Healthy." The
title may say it's for young people but the paper is good for all
ages.
Next up on the page is a short article about diagnostic testing.
The article explains how the tests work in the process and it explains
some of the common terms associated with diagnostic tests with
examples.
Finally on the page is a link to resources related to raw milk
consumption and the potential human health risks. You'll see more
than 16 links to scientific resources covering the various angles
of the raw milk issue. There also are several specific suggested
papers on the topic.
April 06
Part II
The milk flow dance
Stimulating the cow for the peak milk let down dance
prior to unit attachment is determined by the prep/lag procedure.
The general guideline is to continuously stimulate the teats for
20-30 seconds, followed by a lag time of one minute or less, with
a total elapsed time of between 60-90 seconds from when the cow
is first touched to unit attachment.
Recent research suggests that adhering to the lower end of the
recommended timeline, 60 seconds total, is better than exceeding
the upper limit of 90 seconds total. Of course this is for the
average cow so variation from cow to cow is the reality.
When the unit is attached at peak milk letdown, indicated by teats
ballooned with milk, not too early or too late, milking unit "dancing" is
very apparent.
When do units dance with your cows? Is it more than 30 seconds
after attachment? Is it immediately following attachment or with
some cows not at all? An old saying teaches that milking a cow
is a lot like making love, the approach is real important! After
all, it’s a dance.
March 06
The milk flow dance
Perhaps the recent finale of "Dancing with the
Stars" is lingering in my mind. But actually, the thought
has to do with milking cows efficiently without damaging teat-ends.
What in the world does milking cows have to do with dancing? What
I’m referring to is the bouncing and shaking, really pounding
if you do it right, of the milking unit when the cow is at peak
milk flow. You might even agree that at peak flow, the milking
unit and hose literally dance!
Why do we care? A fast milk out minimizes unit on-time which limits
the negative effect vacuum has on teat-end health. Having the unit
on the cow only during significant milk flow minimizes teat-end
damage. Minimizing teat-end damage lessons the risk for mastitis
infections.
Knowing what to do to achieve
peak milk flow (PDF-9 pages) and what it looks
like in practice are important. The goal to achieve is a violently
dancing unit within 30 seconds of attachment, with the dance lasting
for about three
or four minutes (PDF-8 pages) through peak flow, then dropping
off to a gentle, quiet ending lasting no more than another minute
culminating in detachment (Figure 1).
If you see such a dance it means milk
letdown was stimulated (PDF-9 pages) and
achieved followed by immediate attachment of the milking unit and
that peak flow was sustained until very near the end of milking.
By Ken Bolton
Extension Milk Money Team Coach
Feb. 06
Record keeping
Records are the next leg in the mastitis treatment
framework. Keeping the records plan simple and easy, yet comprehensive
enough to be of value for the management of individual cases and
useful in managing the herd mastitis pattern is a challenge. Both
can happen easily with a bit of organization and discipline.
- At detection we initiated a temporary record.
- The information gathered at the examination that affected the
treatment decision is added to the temporary record.
- The entry into the permanent record needs to serve as clinical
mastitis medical history for this individual and still serve
to pattern the clinical mastitis of the herd.
- The temporary record now can be used for daily evaluation of
clinical progress, which supports a trained person responsible
for making adjustments in the original treatment decision or
seeking aid in the event of treatment failure.
- The temporary record can now be used if the dairy wishes an
entry into the permanent record at the completion of the case
that adds information that is useful both for the medical history
of the individual and for patterning clinical effectiveness of
therapies for the herd.
The final step is the process for insuring food safety before
returning the cow to the saleable milk string. Label treatments
need to be held to the full label withdrawal and the withdrawal
for extra-label therapies administered under a valid VCPR need
to be determined in accordance with the Animal
Medical Drug Usage Clarification Act (AMDUCA).
Top of Page...> Jan. 06
Detection and examination
framework
Beyond being a great stimulation
of letdown, pre-stripping also insures early detection of abnormal
milk and is the only way to detect the mild cases that are not
accompanied by tissue inflammation.
Once we have detected the mastitis we need to
divert the abnormal milk from the saleable milk, mark of the clinical
cow for examination, and initiate her mastitis record.
The examination protocol is to identify all the
information useful for making the treatment decision. The parts
of the examination process are:
• Examine the cow
to assess the severity of the case.
• Do a CMT of the
remaining quarters to detect any sub-clinical quarters.
• Culture the case
to determine etiology.
• Examine the medical
history of the cow to be aware of her previous clinical case
history, her sub clinical history, and to be aware of other medical
and relative value history that might impact the treatment decision.
A thorough examination protocol provides the
producer with key information useful for targeted treatment decisions.
Clearly identifying all of the various factors involved in the
case aids in the decision-making process and increase the probability
of a positive outcome.
An example of an exam protocol found here (PDF)Go...>
With so much complexity present in the mastitis
formula, basing treatment decisions on the best possible information
reduces risk in the market and helps the producer manage for the
best economic values. Proper treatment should assist in managing
costs and improving productivity.
David Rhoda, DVM
Extension Outreach Veterinarian
UW Department of Dairy Science
Top of Page...>
Nov. 05
Mastitis Treatment Plans
Writing treatment plans for clinical mastitis is hard. There are
a variety of bacteria that cause mastitis; each bacterium may cause
a gradient of severities of symptoms, and each animal varies in
age, stage of lactation and past clinical and sub clinical medical
histories.
Also we have new medicines entering the market, new technologies
such as on-farm culturing being introduced, and we often need adjustments
in strategies because of other changes in the facility, environment,
or individual pathogen prevalence levels.
Because of such complexity, we need a stable framework for the
process that leads to a treatment decision that is adapted to this
kind of flux and still allow a constructive evolution of treatment
strategies.
A stable framework has a routine detection plan, includes an established
examination protocol, has a formal record keeping plan, and assures
food safety when returning the individual animals’ products
to the consumer market. Such a framework helps dairy producers
adjust to changing situations, manage animal health issues in a
timely, cost-effective fashion while reducing market risk and enhancing
profitability.
In the columns that follow, we'll take a closer look at the pieces
of a mastitis treatment plan that provide a solid framework. Detection,
examination and records are the three legs of the framework that
we'll review.
By David Rhoda, DVM
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Sept. 05
New Tests to Detect Subclinical Mastitis:
The PortaSCC™
The PortaSCC™ (PortaScience,
Portland ME) is a rapid test that
is marketed for cowside testing of somatic cells. This test is
adapted from a product used by human cancer patients to monitor
white blood counts.
The test measures only white blood cells (not epithelial cells)
and has an upper limit of detection of 3,500,000 cells/ml. The
test consists of a small strip that is inoculated with a drop of
milk and a reagent. The test strip requires a 45 minute room temperature
incubation and is read in a small handheld meter.
This test must be performed on fresh milk as the results become
unreliable as milk ages. We evaluated this product using 300 quarter
milk samples obtained from cows located on 10 dairy farms (Amaral,
Hulland and Ruegg, NMC Proceeding, 2004).
The PortaSCC™ was performed on the farm and the values were compared
to values determined using regular laboratory methods. Infections
with major or minor mastitis pathogens were defined based on isolation
from duplicate quarter samples. There was no significant difference
between the SCC determined in the laboratory (92,000 cells/ml)
and the results of the PortaSCC (63,000 cells/ml, P <0.001).
The correlation between the tests was 0.81 (P<0.001). When
subclinical mastitis was defined based on a threshold of 200,000
cell/ml, the two methods agreed about 88% of the time. The PortaSCC™ values for all CMT scores greater than trace were indicative of
probable infection. Somatic cell count values measured using either
traditional laboratory methods or the PortaSCC™ were associated
with infection status and the test appears to be reliable enough
to be used for standard cowside testing.
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July 05
New Tests to Detect Subclinical Mastitis:
The Direct Cell Counter
Pamela L. Ruegg, DVM, MPVM, Associate Professor - University
of Wisconsin, Madison
While the California Mastitis Test (CMT) is used to detect very
high somatic cell counts (SCC), the ability to more precisely
identify quarters with SCC that exceed the threshold of 200,000
-250,000 cells/ml is necessary to reduce the rate of false negative
results.
The
Direct Cell Counter (DCC – from DeLaval) is a new device
that is designed to be used on farms for rapid counting of somatic
cells. Small cassettes are filled with approximately 1µl
of fresh milk, stained automatically in the cassette and inserted
into a small battery operated optical cell counter.
The DCC produces a somatic cell count in less than 1 minute within
the range of 10,000 to 4,000,000 cells/ml. In one experiment we
compared the performance of the Direct Cell Counter to other measures
of mastitis (Ruegg, Hulland and Reith, Proceedings NMC 2005). Quarter
milk samples were obtained from cows during days 3-9 post-calving.
Study personnel used the DCC on the farm and submitted additional
duplicate quarter milk samples for laboratory determination of
SCC and for culturing.
Infections with major or minor mastitis pathogens were defined
based on isolation from both duplicate quarter samples. There was
no significant difference between the SCC determined in the laboratory
(median = 87,000 cells/ml) or the count determined by the DCC (93,000
cells/ml) (P = 0.76). The correlation between the two methods was
0.92 (P<0.001).
When subclinical mastitis was defined based on a threshold of
200,000 cell/ml, the two methods agreed about the diagnosis 95%
of the time. The DCC was higher for milk samples from which major
(1,525,000 cells/ml) or minor (310,000 cells/ml) pathogens were
recovered as compared to milk samples that were negative (79,000)
(P <0.001).
The DCC appears to be an accurate method to rapidly determine
SCC values on the farm and less subjective than the CMT.
Next month we will review another new test: The PortaSCC.
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June 05
Detecting Subclinical Mastitis – Part II
Pamela L. Ruegg, DVM, MPVM, Associate Professor - University
of Wisconsin, Madison
Assessing the Tests – 1. The California Mastitis
Test
For 50 years the California Mastitis Test (CMT) has been used
as a cowside screening test for subclinical mastitis. The CMT does
not identify the type of bacteria that cause mastitis but is used
to identify quarters that have high SCC. The degree of reaction
between the detergent and the DNA of cell nuclei is a measure of
the number of somatic cells in milk. The relationship between SCC
values and CMT is not precise because of the high degree of variability
in SCC values of each CMT score (Table 1).
In general, as CMT reactions increase, the likelihood of recovering
pathogenic bacteria increases. The CMT is good at detecting infections
in quarters that have SCC > 500,000 cells/ml but studies have
shown that infected quarters may be missed when the cell count
is lower. In fact, the rate of false negatives ranges from 8 to
43% depending on the score used as a threshold for infection. Many
infected quarters have cell counts that are between 200,000 – 500,000
cells/ml and to minimize the number of false negative results,
the test should be read as positive when at least a trace reaction
is apparent.
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May 05
Detecting Subclinical Mastitis – Part I
Pamela L. Ruegg, DVM, MPVM,
Associate Professor - University of Wisconsin, Madison
By definition subclinical diseases don’t have overt clinical
signs and must be diagnosed using some sort of test. Subclinical
mastitis is usually diagnosed based on somatic cell count (SCC) values
that exceed a threshold (such as 250,000 cells/ml or linear score
of 4.0). Somatic cell counts are generally monitored using monthly
DHI data. This monthly data is vitally important for mastitis control
programs but it is important to remember that SCC values from DHI
are obtained for milk that has been commingled from all 4 quarters.
The use of composite milk SCC to identify infected cows will always
result in under-diagnosis of subclinical infections because of dilution
of somatic cells with milk from uninfected quarters. Consider the
hypothetical situation when a cow is producing 40 lb of milk per
milking evenly distributed between 4 quarters (10.0 lb per quarter)
but has only 1 quarter infected with subclinical mastitis. If the
SCC of the milk from the 3 uninfected quarters is 100,000 cells/ml,
the composite SCC value will not reach a threshold of 200,000 cells/ml
until the SCC from the infected quarter exceeds 700,000 cells/ml.
Mastitis control program can be improved with the use of simple
cowside tests for further screening of cows suspected to have subclinical
mastitis. The California Mastitis Test (CMT) has been available and
used for this function for >50 years. Recently, several new cowside
screening tests have been developed. Over the next couple of months,
this column will review the performance some of the new tests which
are now available for cowside screening.
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