12 
BULLETIN 147^ XJ. S. DEPARTMENT OF AGRICULTURE. 
cows of the tick-infested group produced an average of 60.6 pounds 
per cow, a decrease of 65.9 per cent when compared with their first 
10-day period. It should be noted especially that while the tick- 
infested cows produced 1 per cent more milk than the tick-free cows 
in the beginning, they produced only 65.8 per cent as much during 
the final period. The two groups consumed practically the same 
TEN-DAY PERIOD ENDING- 
MAY z/UME UU/iE </UHE UULY UULY JULY AUG. AUG. AUG. SEPT. SEPT. 6EPT OCT. 
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Fig. 5.— Average milk production by 10-day periods of the tick-free and tick-infested groups and of 
four heavily infested cows. 
amount of feed during the entire period. The percentage of fat in 
the milk of each group increased toward the close of the experiment, 
that of the infested group showing a slightly greater increase. 
At the beginning of the test the tick-free cows weighed on the 
average 719.2 pounds and the tick-infested 707.2 pounds. During 
the experimental period each group increased in body weight, but 
the increase of the tick-free group was greater than that of the tick- 
