EFFECT OF CATTLE TICK OX MILK PRODUCTION. 



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 cow 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 varving 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 onlv 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-dav 



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. 







period. 



Hay. ; Grain. 



Tick free 



Tick infested 



Lightly infested 



Moderately infested... 

 Heavily infested 



Nos. 1 to 10. . 

 Nos.li to 20.. 



Pound". 

 176.2 

 177.9 



Pounds. 

 92.1 

 60.6 



Perct. 



47.7 

 65.9 



Pounds. 

 719.2 



707. 2 



Pounds. Per ct. 



763. 4 4- 6. 1 

 732. 9 4-3. 6 



i 

 Pounds. Pounds. 

 2,500 1 638 

 2,437 1 658 



Nos. 11, 14, 18, 157. 5 



19. 

 Nos. 16, 17...! 149.4 

 Nos. 12, 13, 15, 212.6 



20. 



68.6 



56.8 



54. 5 



56.4 



61.9 



74.3 



694.4 



746.1 

 700.7 



736. +6. 



809. 4 1 4-8.5 

 691.4 ! —1.3 



1 



2,385 



2, 563 

 2,424 



585 



569 



786 



COMPARISON OF TICK-FREE AND TICK-LNFESTED 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 



