EFFECT OF CATTLE TICK ON MILK PRODUCTION. 
15 
spraying showed reductions, respectively, of 6.2, 21.7, 4.5, and 7.6 
per cent. Disregarding the second spraying, the average reduction 
for five days was (>. i per cent. 
These results with spraying are similar to those obtained with dip- 
ping during the 165-day test conducted by J. H. McClain, of the Dairy 
Division, Bureau of Animal Industry, at Summerville, S. C, in 
1912. In this experiment 10 cows were dipped seven times with a 
solution of tick dip B, the dippings coming at intervals oi about 21 
days, with an average decline in milk production, for two days, of 
10.6 per cent after each of the seven dippings. But apparently the 
cows became accus- 
t omed t o the dipping 
process, for there was 
no appreciable de- 
crease in the milk 
flow after the first 
four dippings except 
the natural decrease 
due to the advance 
in the lactation 
period. The average 
decline in production 
was approximately 
as follows: After 
each of the first four 
dippings, milk 14.8 
per cent; fat 8.9 per 
cent; after each of 
the last three dip- 
pings, milk 1.9 per 
cent, but an increase 
of 10.6 per cent in 
yield of fat. 
That the heavily infested cattle in our experiments yielded fully 
40 per cent less milk than the check animals at the close of the 
experiments, and that even those lightly infested gave less by 25 per 
cent, has been heretofore recorded. Conversely, we may infer that 
the check cows in this experiment and those regularly dipped in the 
Summerville experiment gave this additional quantity of milk on 
account of being kept free from ticks. Had this freedom been 
obtained without the use of arsenical dips, it is quite certain that an 
amount of milk equal to 10.6 per cent during one-tenth of the time 
in the Summerville experiment, and to 6.1 per cent during one- 
seventh of the time in our experiments, would also have been saved 
Fig. 6.— Effect of spraying on milk production, showing the average 
amount of milk produced by the tick-free group for three days before 
and seven days after each of four sprayings. The unusual decline 
at the second spraying was probably due to a change in feed. 
