EFFECT OF CATTLE TICK ON MILK PRODUCTION. 
11 
definite results until toward the latter part of the experimental 
period. 
The cows used were so-called immune, yet all the tick-infested 
group except the four lightly infested ones suffered from attacks of 
fever at different times during the experimental period. This was 
not due entirely to the number of ticks maturing upon these animals, 
for eow 15, which showed the heaviest infestation throughout the 
entire period, was one of the last to suffer from an attack of fever. 
EFFECT OF TICKS ON MILK PRODUCTION AND BODY WEIGHT. 
Although each of the cows used in this work had been tick infested 
at some time, the individual variation in the degree of infestation 
that could be obtained was so wide that two subgroups were made 
of four animals each, one of which will be called the lightly infested 
and the other the heavily infested group. These subgroups show the 
effect of varying degrees of infestation upon the body weights and 
milk production of the cows in a manner more marked than when 
the two entire groups are compared. In the discussion which fol- 
lows only the summaries of groups are given. Complete data for each 
cow will be found in the appendix. The average results are shown 
in Table 3 following, and graphically in the chart, figure 5. 
Table 3. — Effect of tick infestation on milk production and body weight of cows. 
Number of 
cows. 
Milk production. 
Body weight. 
Feed. 
Group. 
Aver- 
age for 
first 
10-day 
period. 
Aver- 
age for 
last 
10-day 
period. 
Aver- 
age de- 
crease. 
Aver- 
age for 
first 
10-day 
period. 
Aver- 
age for 
last 
10-day 
period. 
Aver- 
age 
gain 
( + ) 
or loss 
Average con- 
sumption 
per cow for 
entire period. 
Hay. 
Grain. 
Tick free 
Tick infested 
Nos. 1 to 10.. 
Nos. 11 to 20.. 
Pounds. 
176.2 
177.9 
Pounds. 
92.1 
60.6 
Per ct. 
47.7 
65.9 
Pounds. 
719.2 
707.2 
Pounds. 
763. 4 
732.9 
Per ct. 
+6.1 
+3.6 
Pounds. 
2,500 
2,437 
Pounds. 
638 
658 
Lightly infested 
Moderately infested... 
Heavily infested 
Nos. 11, 14, 18, 
19. 
Nos. 16, 17... 
Nos. 12, 13, 15, 
20. 
157.5 
149.4 
212.6 
68.6 
56.8 
54.5 
56.4 
61.9 
74.3 
694.4 
746.1 
700.7 
736.0 
809.4 
691.4 
+6.0 
+8. 5 
-1.3 
2,385 
2,563 
2,424 
585 
569 
786 
COMPARISON OF TICK-FREE AND TICK-INFESTED COWS (ENTIRE GROUPS). 
At the beginning of the experimental period the two groups pro- 
duced practically the same amount of milk — the cows of the tick-free 
group producing an average of 176.2 pounds during the first 10-day 
period and those of the tick-infested group an average of 177.9 
pounds. During the final 10-day period the cows of the tick-free 
group produced an average of 92.1 pounds of milk, a decrease of 47.7 
per cent from their production during the initial period, while the 
