2. Research Topic
This study takes a look at a common
infection in dairy cattle called mastitis
and tries to find a connection between
individual cow hygiene and mastitis
infection.
3. Aim
The objective of this study was to
determine if there is a relationship
between hygiene scores of lactating dairy
cattle and measures of subclinical
mastitis.
4. Rationale
My reason for choosing this topic was that I
wanted to do a research project that reflected
my interest in animal science.
Also this area of research needs to be explored
in more detail in Trinidad and the wider
Caribbean region as there is not enough data
on this topic.
5. Background
Mastitis is defined as
an inflammation of
the mammary gland.
It is the most common
infection in the dairy
sector that results in
changes in milk
composition.
6. Constituent Normal milk (%) Mastitic milk (%)
Solid non fat 8.98 8.8
Fat 35.0 3.20
Lactose 4.90 4.40
Total protein 3.61 3.56
Total casein 2.8 2.30
Whey protein 0.8 1.30
Serum albumin 0.02 0.07
Lactoferrin 0.02 0.10
Immunoglobulin 0.10 0.60
Sodium 0.06 0.105
Chloride 0.09 0.147
Potassium 0.17 0.157
Calcium 0.12 0.04
Example of compositional changes found in various studies.
7. Mastitis is the main
reason for economic
losses within the dairy
cattle industry.
Milk becomes unfit for
human consumption.
Production losses
High veterinary
treatment costs.
8. Causes of Mastitis
Mastitis is primarily
caused by bacteria.
It is classified into
two major groups:
Contagious Mastitis
and Environmental
Mastitis.
10. Environmental Pathogens
Coliforms
Escherichia coli
Environmental
streptococci
S. uberis
S. bovis
S. disgalactiae
Enterococcus faecium
Enterococcus faecalis
11. Progression of the Infection
The udder is comprised of
four distinct secretory
glands called “quarters.”
Each quarter consists of
milk producing secretory
tissue, known as alveoli.
12. Progression of the Infection
The bacterium enters the
glandular tissues and
affects the alveolar cells.
The bacterium produces
toxins which damage and
even kill the milk-secreting
epithelial cells.
13. Mastitis can be
manifested in three
different ways:
Subclinical
Clinical
Chronic
14. Subclinical form important because…
It is 15 to 40 times more prevalent than the
clinical form.
It usually precedes the clinical form.
It is of longer duration and difficult to detect.
It adversely affects the quality of milk.
15. 87%
4%3% 5% 1%
Percentage of substances
in normal cow’s milk
Water Fat Protein
Lactose Minerals
Since subclinical
mastitis cannot be
visualized, the only
way to detect it is by
measuring the cellular
content of the milk.
16. Normal milk also contains
white blood cells.
Whenever there is an
infection such as the
invasion of bacteria the
white blood cells located
around the infected area
increase dramatically in
numbers (millions/ml).
17. The CMT is a simple test that
is commonly used to detect
subclinical mastitis.
The CMT can correctly predict
the somatic cell count of milk
from composite milk samples.
California Mastitis Test
(CMT)
18. CMT Kit
A CMT Kit includes a four
chambered paddle, a
concentrated reagent, an empty
pump bottle and complete
directions and color charts.
19. About ½ teaspoon of milk is dispensed from each quarter into
each of the four chambers of the paddle.
Conducting the CMT
20. An equal ratio of reagent is poured into the milk and the paddle
is rotated in a circular motion to thoroughly mix contents.
Conducting the CMT
21. The reagent reacts with the white blood cells and the
mixture thickens or gels in proportion to the amount of
infection present.
Conducting the CMT
22. CMT Scoring Chart
Leukocyte
count per
millilitre
Test appearance CMT
score
Below 200,000 Mixture liquid, no precipitate negative
150,000 to 500,000 Slight precipitate, tends to
disappear with paddle
movement
Trace
400,000 to
1,500,000
Distinct precipitate but does not
gel with paddle movement
1
800,000 to
5,000,000
Distinct gel formation 2
Over 5,000,000 Strong gel formation that tends
to adhere to paddle. Forms
distinct central peak
3
26. Hygiene Scoring
The environment the cow
lives in greatly influences the
numbers and types of bacteria
that they are exposed to.
Hygiene scoring is an
effective way of providing
visible evidence of the
amount of exposure a cow
has to a particular
environment.
27. Transfer Mechanisms
Environmental streptococci
such as S. uberis and S.
dysgalactiae are mainly found
in manure.
Manure can transfer to the
udder in four different ways:
direct transfer
leg transfer
Splashing
tail transfer
28. Hygiene Score
Hygiene scoring systems have
been developed to assess the
cleanliness of the cows.
Three zones - lower leg, udder
and upper leg and flank area.
Score each zone separately
using numbered system with 1
(very clean) and 4 (very dirty).
32. Results of Hygiene Score
0
20
40
60
80
100
120
140
160
180
200
v. clean
"1"
clean "2" dirty "3" v. dirty
"4"
Percentageofcows
Hygiene Scores
Upper leg
and Flank
Lower leg
Udder
33. Analysis of Results
The relationship between hygiene scores and
measures of subclinical mastitis was strong.
All of the animals were characterized as clean
and were free of subclinical mastitis.
Due to the small sample size the data could
not be analyzed with a statistical program.
34. Conclusion
Therefore, this study was unable to precisely
confirm the relationship between measures of
subclinical mastitis and udder and leg hygiene
scores.
35. Recommendations
A larger study that incorporates several study
farms over a period of at least six months is
needed.
Further laboratory analysis of milk samples is
also needed to identify if the bacteria were
predominantly contagious or environmental
pathogens.
