EFFECT OF CATTLE TICK OK MILK PRODUCTION. 
Cow L2, a mongrel Jersey with black predominating and white 
under parts, was the next most infested. (Fig. 3.) She became ill 
but acquired the habit of licking herself as clean of ticks as she could 
and of being assisted by other cows. She seemed to recover from 
her fever and improved somewhat in condition. 
Cows 13, 16, and 17 were infested about alike, but Nos. 13 and 17 
suffered more from fever than No. 16. There seemed to be no par- 
ticular difference in the coats of Nos. 13 and 16 sufficient to explain 
why No. 10 should be less infested. They were red cows of mixed 
origin and doubtful ancestry. Cow 17 (fig. 4) was a very dark 
cow with white under parts, hav- 
ing a rather fine Jersey-like head. 
The sickness reduced her milk flow 
much more than was the case with 
No .13. As a whole, the light fawn- 
colored cows seemed to resist ticks 
better than the dark-colored ones. 
The sickness in the cattle was 
not entirely due to the number of 
ticks, for cows that had fewer ticks 
by far than cow 15 were sick much 
earlier. It has previously been 
stated that one of the sources of 
ticks was the Anthony farm. This 
farm sustains a large dairy, and fre- 
quently the herd is replenished 
with fresh milkers brought from 
Georgia and the surrounding coun- 
try. According to the superin- 
tendent, many go through acclima- 
tization or Texas fever. It is quite 
probable that ticks from some of 
the acclimatized animals furnished 
the first protozoa (piroplasma) to 
produce disease in the experimental 
animals; it may be that afterwards ticks from sick cows in the ex- 
periment transferred the disease to other cows. While all these cattle 
w T ere used to ticks, it is quite evident that they were not thoroughly 
immune to fresh attacks of disease, whether due to blood-letting or 
piroplasma parasitism. That immunity is a variable quantity is 
accepted by many southern cattlemen who have studied and had 
experience with traded cattle. 
The 10 check cattle remained free from ticks through keeping them 
in a separate pen and stalls; otherwise they were under similar condi- 
tions as the infested cattle. Although they were separated from the 
58970°— Bull. 147—15 2 
Fig. 3, 
-Cow No. 12, heavily infested on rear par 
Photo taken July 19, 1913. 
