EFFECT OF CATTLE TICK ON MILK PRODUCTION. 



Cow 12, 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. 16 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 

 were 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 parts. 

 Photo taken July 19, 1913. 



