NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
356 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [VI, IV
Samples were taken from each quarter direct into specially-made centrifuge tubes
of 10 c.c. capacity. (2) Observation of the chemical reaction, and of the amount
and character of the deposit after centrifuging. (3) Plating of the deposit in blood
agar plates if it was 0.01 c.c. or above [since 1933, blood agar containing crystal
violet 1 : 500,000 and æsculin 0.1 per cent (Edwards, 1933)]; sowing of deposit
into an enrichment medium consisting of serum glucose broth containing
1 : 200,000 crystal violet [Edwards, 1930] if it was below 0.01 c.c. (4) Verification
of streptococcus colonies by the fermentation and other tests previously outlined.
Since 1932 growths have also been checked serologically, using sera specific to
the types already defined [Stableforth, 1932].
Notes.—The term " Infected " in this report signifies cows infected with Str.
agalactiæ. The terms " Group II " and " Group III " refer to mastitis strepto-
cocci so designated in previous studies [Minett, Stableforth and Edwards, 1929 ;
Edwards, 1932].
HERD A
In 1929, when the work was started, the milking herd numbered 55 animals,
viz., 45 Shorthorns and 10 Ayrshires. During 1930 most of the Shorthorns were
replaced by Ayrshire heifers, the numbers of which have been gradually increased,
year by year, until the end of 1935, the herd consisted of 146 animals, nearly all
Ayrshires. Latterly, the herd has been entirely self-contained. It is free from
tuberculosis, certified milk being produced, and the proportion of cows reacting
to the test for contagious abortion is now negligible. Milking is carried out by
machine thrice daily. Hand stripping is not done.
The usual practice has been to retain in the herd animals infected with Str.
agalactiæ and to segregate them at one end of the milking shed or to put them
into a special " infected " shed or line. The arrangements have varied from
time to time according to the number of infected cows and the accommodation,
but infected animals have invariably been milked last or with a special machine
unit. The owner has also taken immediate steps to prevent spread of disease
from any animal showing signs of udder disturbance.
HERD A
State of Herd at end
of Year
Year
1929
1930
1931
1932
1933
1934
1935
Total
55
71
112
126
128
159
146
Healthy
50
68
103
78
84
113
117
Infected
5 (9.1)
3 (4.2)
9 (8.0)
48 (38.1)
44 (34.5)
46 (28.9)
29 (19.9)
Additions, Removals and Cows which became
Infected during previous 12 Months
Healthy
became
Infected
–
1 (2.0)
6 (8.8)
50 (48.5)
13 (16.7)
12 (14.3)
6 (5.3)
Healthy
Added
–
71
48
37
40
53
38
Healthy
Removed
–
52
7
12
21
12
28
Infected
Added
–
0
0
1
2
0
0
Infected
Removed
–
3
0
12
19
10
23
358 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [VI, IV
actually infected at December 31st, 1934, was 19 per cent, whilst at November,
1935, it was 13.1 per cent. In those infections which became permanent the
degree of disturbance was slight at first, but during the last twelve months many
of the cows concerned have shown symptoms characteristic of the chronic forms
of the disease.
Herd A is also notable for the relatively large number of severe cases of mas-
titis due to other causes, and especially to streptococci belonging to Group II,
which have occurred. In this herd, contrary to the almost general rule, such
infections have been the cause of much greater loss than mastitis of the common
chronic type.
HERD C
Her d C is made up of pedigree Jerseys and Red Polls, and from 1929, when
observations commenced, it has carried over 100 head of milking stock. The
herd has always been practically self-contained, though a few animals have been
purchased from time to time. The herd is free from tuberculosis, certified milk
being produced, and has been freed from contagious abortion by blood tests and
segregation, coincidentally with the work reported here. Milking is carried out
by hand.
HERD C
State of Herd at end
of Year
Year
1929
1930
1931
1932
1933
1934
1935
Total
86
101
86
111
113
116
134
Healthy
53
72
61
62
68
75
99
Infected
34 (39.5)
29 (28.7)
25 (29.1)
49 (44.1)
45 (39.8)
41 (35.3)
35 (26.1)
Additions, Removals and Cows which became
Infected during previous 12 Months
Healthy
became
Infected
—
10 (29.4)
4 (5.6)
35 (57.4)
11 (17.7)
12 (17.6)
7 (9.3)
Healthy
Added
—
55
10
43
25
31
39
Healthy
Removed
—
26
17
7
8
12
8
Infected
Added
—
3
0
4
2
0
0
Infected
Removed
—
18
8
15
17
16
13
For explanation see table for Herd A.
Of the 35 cows classed as infected in 1935, 11 had been free from infection for
at least two years. The number of cows actually infected at the end of 1935 is, there-
fore, 24 and the real incidence 17.9 per cent.
Up to the end of 1931 mastitis-infected cows were kept in the same sheds as
the uninfected, but segregated at one end and milked last. From 1932 onwards
infected animals were removed to other sheds and milked by separate attendants.
During the first four years heifers were milked after the older healthy animals
until they had passed a test seven to ten days after calving. Since the middle
STUDIES ON BOVINE MASTITIS
359
of 1932 they have been milked first of all. In addition, the owner has always
insisted that milkers should wash their hands after milking each cow and all rea-
sonable precautions were taken to prevent spread from infected to healthy animals.
Complete herd tests of all animals in milk were carried out every three months
in the case of the healthy group and at six- to twelve-monthly intervals in the
infected group. Samples were also examined seven to ten days after calving,
and from any animal whose milk or udder became abnormal during the interval
between herd tests. The total number of animals in the healthy section of the herd
in December, 1929, or which have since entered this section (" Healthy added ")
is 256. Of these 256 cows, 72 were under observation for one lactation or
less, 74 for two lactations, 47 for three, 32 for four, 24 for five and 7 for six lacta-
tions. The number of tests made of each cow was from 2 to 17 and in one case
24, a total of 1,621 or an average for each animal of between 6 and 7. The table
shows the number of healthy and infected animals in the herd at the end of each
year and the movements during the preceding twelve months.
The clinical severity of the disease originally present may be gathered from
the following statements. By the end of 1929 all the original milking herd had
been tested, except four cows which were still dry. Of the 34 infected cows present
at that time, 17 were showing clinical symptoms or obviously altered milk
in one or more quarters ; 8 showed abnormality of the milk only recognisable by
laboratory examination, whilst in 9 the milk was unchanged. The average number
of infected quarters per animal was 2.4.
Comment
In this herd no special attempt was made to dispose of infected cows, but
they were immediately segregated, and what were expected to be ample precau-
tions were taken to prevent spread of infection. Although there has always
been a large group of infected cows on the farm in sheds adjoining those kept for
healthy cows, it is somewhat surprising that new infections have continued to
appear. Thus, of the 256 animals which were passed as healthy when first tested
in the period 1929-35, 79 had become infected up to the end of 1935. Although
dropping to less than 6 per cent in 1931 the annual percentage of new infections
rose suddenly to over 50 in 1932. It dropped again to 17 per cent in 1933 and
1934, whilst in 1935, 9 per cent have occurred. The result is that the section
described as infected, which was originally 39 per cent of the herd, still forms
26 per cent of it. As in Herd A a number of animals apparently recovered. These
were, in nearly all cases, animals in which the infection was discovered only by
means of the glucose broth enrichment medium and on only one occasion, in spite
of numerous examinations during the succeeding years. Since such cows have
always been classed as infected the number of animals shown as infected is, in this
herd also, unduly high for all years since 1932. The real incidence at the end of
1935 was 17.9 per cent.
360 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [VI, IV
As in other herds, a certain amount of trouble due to mastitis streptococci
of Groups II and III and to C. pyogenes has occurred, 18 cows in all being affected.
HERD I
At the end of 1930, when the first examinations were completed, Herd I con-
sisted of about 160 head of pedigree milking stock of the British Friesian and
Shorthorn breeds. It has been maintained since that time solely by means of
home-bred animals. The herd is tuberculin-tested and it has been freed from
contagious abortion coincidently with the work reported here. Milking is carried
out by machine three times a day and all cows are stripped by hand.
After the first herd test infected animals were segregated as far as possible,
and milked last. In 1931 the cows were arranged on three standings of which
one contained only healthy cows, one healthy and infected at opposite ends, and
one infected cows only, one man doing all the work on each line. Three milking
machine units were in use in each row, separate units being reserved for the
infected cows in the composite line. Teat cups were sterilised at the beginning
of milking but not subsequently unless they were dropped. Towards the end of
1931 the owner decided to reduce his herd considerably and amongst those sold
were most of the infected cows. From March, 1932, the few remaining infected
cows were moved to other buildings.
HERD I
State of Herd at end
of Year
Year
1930
1931
1932
1933
1934
1935
Total
158
125
65
61
81
79
Healthy
71
76
61
61
81
79
Infected
87(55.1)
49(39.2)
4(6.2)
0
0
0
Additions, Removals and Cows which became
infected duering the previous 12 Months
Healthy
became
Infected
—
16(22.5)
9(11.8)
0
0
0
Healthy
Added
—
60
37
31
34
18
Healthy
Removed
—
39
43
31
14
20
Infected
Added
—
7
2
0
0
0
Infected
Removed
—.
61
56
4
0
0
For explanation see table for Herd A.
Milk samples were examined every three months. Samples were also taken
from individual cows seven to ten days after calving, and from any animal which
was giving altered milk or which showed any clinical abnormality of the udder
or reacted to tests with brom-cresol-purple paper which were regularly carried
out at the farm. The total number of animals passed into the healthy section of
the herd in 1930 or which have since entered this section (" Healthy added ") is
251. Of these 251, 118 were under observation for one lactation or less ; 96 for
two lactations ; 22 for three ; 10 for four, and 5 for five lactations. The number
of tests made of each cow was from 2 to 22, totalling 1,476 or an average of
about 6 for each cow.
STUDIES ON BOVINE MASTITIS
361
The table, giving the changes in the herd year by year and its composition at
December 31st of each year, shows that at the end of the third year the herd was
free from Str. agalactiæ and has remained so since that time.
The mastitis originally present was of the characteristic chronic variety caused
by Str. agalactiæ. The following data regarding the changes observed on one
or more occasions will give some idea of its severity. Of the 96 cows of the original
herd which were infected at their first examination in 1930 to 1932, 30 showed
at or about the time of test clinical symptoms and obviously abnormal milk,
54 showed definite laboratory evidence of mastitis, whilst in 12 the milk was un-
altered. The average number of infected quarters per cow was 2.6.
Comment
In Herd I the contagious form of streptococcus mastitis was radicated within
a reasonable period in spite of the high original incidence (55 per cent) and the
fact that for the first 18 months infected cows were housed in the same shed as the
healthy. It is to be noted, however, that during the first 18 months many animals
in the healthy group showed new infections, viz., 22 per cent in 1931 and 12 per
cent in 1932, a circumstance which there is reason to believe may have been due
in some measure to slackness on the farm. There is no doubt, of course, that the
eradication of the disease from this herd was facilitated very considerably by the
decision of the owner in the autumn of 1931 to reduce his stock. Most of the in-
fected cows were sold then or during the first half of 1932, and other infected cows
were from that time completely separated.
Apart from mastitis due to C. pyogenes, which has caused the loss of a small
number of quarters, the herd has been strikingly free from obvious udder distur-
bance due to streptococci other than Str. agalactiæ and during the last three years
there has been practically no mastitis of any kind.
HERD J
This herd belonged to the same owner as Herds K and L, to be described
next. Infected animals from Herds J and K were sent to other premises for isola-
tion. There has been some interchange between the animals of Herds J and K,
although different attendants were used on the two farms. Early in 1933 it was
decided to raise a new herd on another farm, starting with freshly calved heifers.
This is designated Herd L.
Herd J consists of about 45 animals of the Ayrshire breed and is maintained
entirely by home-bred stock. It is free from tuberculosis ; the eradication of con-
tagious abortion was begun in 1932, and at recent tests there were no reactors.
Milking is carried out by machine and all cows are stripped by hand.
The first tests for mastitis were carried out in November, 1931 and by the
end of 1932, 55 animals of the original herd had been tested for the first time. Of
these 55 animals, 16 (29.1 per cent) were infected,
362 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [VI, IV
All animals in milk were examined at intervals of three months during 1932
and subsequently at six-monthly intervals. All found to be infected at the first
or later tests were removed as soon as convenient to the owner. Post-calving
samples were not examined and animals found to be infected at any given test
had, therefore, already been in the herd for some time. As mentioned, up to the
end of 1932, 16 animals were recognised as infected at their first tests; in 1933
one such animal was located. The total number of animals classed as healthy
at their first test in 1931 or subsequently was 92. Of these 92, 16 were under
observation for one lactation or less, 32 for two, 20 for three and 24 for four lacta-
tions. The number of examinations made of each cow was from 2 to 11, a total
of 464 or an average of about 5 for each animal. The table shows the number
of animals in the herd at the end of each year and the movements during the
previous twelve months.
The general character of the mastitis originally present, which was almost
solely of the common chronic type, can be gathered from the fact that of the 16
cows of the original herd found to be infected, 4 showed at or about the time of
test clinical symptoms or marked change in the milk, 9 showed definite laboratory
evidence of mastitis, whilst in 3 the milk was unchanged in any way. The average
number of infected quarters was 2.
HERD J
Year
1931
1932
1933
1934
1935
State of
Herd at end of
each Year
30
31
55
45
45
Additions, Removals and Cows which
became infected during previous 12
Months
Healthy
became
Infected
—
6(20.0)
3 (9.7)
5(9.1)
3 (7.0)
Healthy
Added
—
9
34
8
11
Healthy
Removed
—
2
7
13
8
For explanation see table for Herd A.
Comment
Although originally nearly one-third of the cows in this herd were infected,
it is somewhat surprising that the infection has not been eradicated, since infected
cows were removed to another farm. It is encouraging, however, that, whilst
the number of animals in the herd has increased, the proportion of new infections
dropped to less than 10 per cent in 1933 and 1934, and to 7.0 per cent in 1935.
Failure to eradicate the disease may have been due to the relatively long intervals
STUDIES ON BOVINE MASTITIS
363
between samplings and because newly added cows—many of which were infected—
were not examined until the next herd test ; also because cows found to be infected
were sometimes not removed for weeks or months. With one exception the
herd has been free from mastitis due to causes other than Str. agalactiæ, whilst
obvious mastitis due to this organism has disappeared, such infections as have
occurred being detectable by laboratory methods only.
HERD K
This herd now consists of about 50 animals of the Friesian, Ayrshire and
Guernsey breeds. It is maintained solely by homebred stock, and is free from
tuberculosis. The eradication of contagious abortion was begun in 1932 and the
herd is now free from reactors. Milking is carried out by hand.
Mastitis control was begun in November, 1931, and by the end of 1932, 93
animals of the original herd had been examined for the first time. Of these 93
animals, 50 (53.8 per cent) were infected.
HERD K
Year
1931
1932
1933
1934
1935
State of
Herd at end of
each Year
36
27
40
56
49
Additions, Removals and Cows which
became infected during previous 12
Months
Healthy
became
Infected
—
16 (44.4)
9(33.3)
4(10.0)
4(7.8)
Healthy
Added
—
7
31
30
21
Healthy
Removed
—
0 9
11
23
For explanation see table for Herd A.
All animals in milk were examined at intervals of three months during 1932
and subsequently at six-monthly intervals, those found to be infected at the
first or subsequent tests being removed as soon as convenient to the owner. Post-
calving samples were not examined and animals found to be infected at any given
test had, therefore, been in the herd for some time. As already stated, 50 animals
were found to be infected at their first test up to the end of 1932 ; in 1933 and 1934
the corresponding numbers were 7 and 3. The total number of animals classed
as healthy at their first test in 1931 or subsequently was 125. Of these 125, 46
were under observation for one lactation or less, 39 for two lactations, 30 for three
and 10 for four lactations. The number of examinations of each cow was from 2
to 10, a total of 480 or an average of nearly 4 for each animal. The table shows
the number of animals in the herd at the end of each year and the events during
the previous twelve months.
364 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [VI, IV
The general character of the mastitis originally present, which was almost
solely of the common chronic type, can be gathered from the following data : of
the 50 cows of the original herd found to be infected 8 showed, at or about the
time of test, clinical symptoms or marked naked-eye changes in the milk, 31
showed definite laboratory evidence of mastitis, whilst in 11, the milk was un-
changed in any way. The average number of infected quarters was 2.6.
Comment
Although since infected cows were removed, it might perhaps have been
expected that the disease would by now have been eradicated, the fact that the
number of infections has steadily fallen whilst the herd has been increasing is
satisfactory. Thus, whereas the original percentage of infection was over 50
per cent, the percentages of new infections in 1932, 1933, 1934 and 1935 were
44, 33, 10 and 7.8 respectively. Failure to eradicate the disease may have been
due to the same factors as operated in Herd J. The herd has been entirely free
from mastitis due to causes other than Str. agalactiæ, whilst mastitis due to this
organism has been confined to latent cases.
HERD L
This herd was formed early in 1933 from freshly calved Ayrshire heifers
belonging to the owner of Herds J and K. It is free from tuberculosis and con-
tagious abortion. The animals are hand-milked.
Tests were carried out at intervals of six months and any infected animals
at once removed. Post-calving samples were not taken. The total number
of animals which have come under observation is 48, of which 13 have been in the
herd for one lactation or less, 16 for two and 19 for three. During this period
they have been examined 2 to 9 times—a total of 266 examinations or an average
of between 5 and 6 for each cow.
The state of the herd in February of 1933 and at the end of each year and the
events during the preceding twelve months are shown in the table.
HERD L
Year
1933 (Feb.)
1933
1934
1935
State of
Herd at end of
each Year
22
32
30
31
Additions, Removals and Cows which
became infected during previous 12
Months
Healthy
became
Infected
—
1
1
0
Healthy
Added
—
12
6
8
Healthy
Removed
—
1
7
7
For explanation see table for Herd A.
STUDIES ON BOVINE MASTITIS
365
Comment
Of the 23 heifers drafted to this herd at the beginning of 1933, one was found
infected at the first test. Twenty-six other heifers have been added and up to
the time of this report two have been found to be infected. Although it was
hoped that no infection at all would appear in this herd, the results are satis-
factory so far as they go and show that when newly-calved heifers are kept apart
from older cows the spread of Str. agalactiæ can be prevented.
Apart from one heifer which showed some disturbance in two quarters, due
to Group III streptococci, the herd has been free from udder disturbance of any
kind.
THE INCIDENCE OF INFECTION IN COWS OF DIFFERENT AGES
In Table 6 is given a summary of the data obtained at the beginning of our
work in Herds C, I, J and K, to show the incidence of infection in cows of different
ages. In these herds the original incidence of infection was 36.2, 55.1, 29.1
and 53.8 per cent respectively. Whilst the actual figures for age incidence vary
somewhat in the individual herds, there is a gradual increase of infection with
succeeding lactations, and it is seen that unless precautions are taken to protect
heifers from infection as many as 30 per cent may become infected in their first
lactation. These findings are similar to those of others, e.g., Seelemann (1932).
TABLE 6
INCIDENCE OF Str. agalactiæ IN RELATION TO THE NUMBER OF LACTATIONS
Herd
C
I
J
K
Total
1st Lactation
Total
34
54
17
20
125
Number
affected
2
14
1
6
23
Per cent
5.9
25.9
5.9
30.0
18.4
2nd Lactation
Total
23
61
7
12
103
Number
affected
7
38
1
3
49
Per cent
30.4
62.3
14.3
25.0
47.6
Herd
C
I
J
K
Total
3rd Lactation
Total
14
32
8
11
65
Number
affected
8
23
2
9
42
Per cent
57.1
71.9
25.0
81.8
64.6
4th to 10th Lactations
Total
23
11
23
50
107
Number
affected
17
11
12
32
72
Per cent
73.9
100.0
52.2
64.0
67.3