EFFECT OF CATTLE TICK ON MILK PRODUCTION. 13 
Infested. During the final LO-day period the cows of the tick-free 
group averaged 763.4 pounds in weight, an increase of 6.1 per cent, 
and those of the tick-infested 732.9 pounds, an increase of 3.6 per 
cent from the initial weight. 
In making this comparison it should be remembered that during 
the entire experimental period the two groups consumed practically 
an equal amount of nutrients, and that toward the latter part of the 
experimental period the milk production of the tick-infested group 
was considerably decreased, so that this group was fed an amount 
in excess of that required for milk production. Presumably this 
excess of food would tend to make flesh and thus offset any detri- 
mental effect that the ticks would have upon the body weights. 
COMPARISON OF TICK-FREE AND HEAVILY INFESTED GROUPS. 
Four cows in the tick-infested group were soon found to be more 
easily infested than the remaining six. A gross infestation of these 
four cows was obtained early in the experimental period and was 
maintained throughout the test. At different times all four suffered 
from attacks of fever, with an almost total loss of appetite and a 
falling off in milk flow. One, which suffered from an attack of fever 
at the end of the experimental period, died shortly after the close of 
the work. 
By referring to Table 3 it will be noticed that there is a much 
more pronounced decrease in milk production between this group 
and the tick-free group than when the two entire groups are com- 
pared, showing that the heavier degree of infestation results in a 
proportionately increased injury. This is likewise proved to be true 
when the body weights of the two groups are compared. 
COMPARISON OF TICK-FREE AND LIGHTLY INFESTED GROUPS. 
While four cows of the tick-infested group proved to be easily 
infested, another four of the same group proved to be very resistant. 
The immature ticks were applied to these four cows with the same 
care and in as large numbers as they were to the heavily infested 
animals; in fact, extra efforts were made to obtain a heavy infesta- 
tion upon these resistant animals. However, at no time during the 
experimental period were any of the four so heavily infested that the 
degree of infestation could be classed as gross, and for the greater 
part of the period none of them was carrying mature ticks. The 
decrease in milk production was more than in the tick-free cows, but 
considerably less than in the heavily infested animals. 
COMPARISON OF LIGHTLY INFESTED AND HEAVILY INFESTED GROUPS. 
While the heavily infested cows produced more milk during the 
initial' period and through the greater part of the experiment, they 
also consumed more feed than those of the lightly infested group 
