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 |
State of |
Additions, Removals and Cows which |
||
|
Healthy |
Healthy |
Healthy |
||
|
1931 |
30 |
— |
— |
— |
|
1932 |
31 |
6(20.0) |
9 |
2 |
|
1933 |
55 |
3 (9.7) |
34 |
7 |
|
1934 |
45 |
5(9.1) |
8 |
13 |
|
1935 |
45 |
3 (7.0) |
11 |
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