June, 1955] B. C. BASU, C. M. SEN GUPTA AND P. BALARAMA MENON 107
It will be noticed that excepting in Group IV the improvement in milk yield
continued in all the groups of the experiments, even though the spraying had actual-
ly been stopped. This can only be attributed to the continued effect which the
spray had in keeping the population of ectoparasites in check. Not much im-
portance can be attributed to Group IV as it received the spray only once in the
beginning of the month. The effect of the spray did not last long which might be
due to various reasons, namely, cleaning, washing, etc. Moreover, two animals
of this batch had to be discarded in the middle of the experiment as they fell ill.
There was also a slight variation in the results during the period of spraying and its
after-effects between groups I and II.
In a previous series of experiments [Basu et al., 1952] when the animals were
sprayed daily with a 0.001 per cent solution of DDT, we recorded a maximum
apparent increase in milk yield of 11.3 per cent during the month of spraying and
11.0 per cent during the month following spray. In the present series, the
daily spraying of the animals with a solution of BHC at the same strength of 0.001
per cent gave a maximum apparent increase of 11.6 per cent and 2.6 per cent respec-
tively during and following the months of spraying. It is interesting to note that
though BHC showed a slightly better effect during the spraying period, its effect
did not last as long as that of DDT when the spraying was discontinued.
SUMMARY
In order to ascertain the effect of the control of ectoparasites on the milk yield
of cattle, gamma BHC in dilutions of 0.001 per cent, 0.002 per cent, 0.003 per cent
and 0.005 per cent was tried on sixteen dairy cows divided into four batches of four
each and four more were kept as control. The spraying was conducted for a month
and about 60 c.c. of the solution were sprayed per cow per operation.
The animals in batches I, II, III and IV were sprayed once with a 0.001 per cent
solution every day, with 0.002 per cent solution every alternate day, with 0.003
per cent solution every week and with a 0.005 per cent solution at the beginning
of the month, respectively. The animals of batch V remained as control.
The milk record was maintained for the period during which the spraying opera-
tion was carried out and also for one month preceding and following it.
Of the four different trials, daily spraying of 0.001 per cent of gamma BHC
was found to be most effective as it showed an increase of 11.6 per cent in milk
yield when compared with control. Likewise batch II had shown an increase of
9.9 per cent, batch III—5.4 per cent and batch IV—3.1 per cent.
ACKNOWLEDGMENT
The authors express their thanks to Dr S. Datta, Director, Indian Veterinary
Research Institute, for giving all possible facilities for conducting this work. They
are specially grateful to Dr P. Bhattacharya, Head of the Division of Animal Genetics,
for allowing them to use the experimental herd attached to his Division.
REFERENCE
Basu, B. C. , Sen Gupta, C. M. and Menon, P. B. (1952). Reduction in milk yield in Indian dairy cattle
by arthropod invasion and its control. Indian J. vet. Sci., 22, 1, 51-59