16 BULLETIN 147, U. S. DEPARTMENT OF AGRICULTURE. 



from loss on account of the ticks. These differences emphasize the 

 good results of the use of arsenical dips, and above all, of the necessity 

 for the complete eradication of ticks so that the remedy, which of 

 itself temporarily reduces the flow of milk, will be unnecessary. 



SUMMARY AND CONCLUSIONS. 



The cattle tick has a decidedly injurious effect upon supposedly 

 immune dairy cattle, the extent of the injury being largely dependent 

 upon the degree of infestation. The effect is more pronounced upon 

 the milk production than upon the. body weights when a sufficient 

 supply of food is given. 



At the beginning of the test the tick-free and tick-infested groups 

 gave practically the same amounts of milk; at the close the tick- 

 infested gave only 65.8 per cent as much as the tick-free. 



The tick-free group gained 6.1 per cent in body weight; the tick- 

 infested gained 3.6 per cent. 



Spraying or dipping tick-free cattle in an arsenical solution causes 

 a marked though temporary decrease in milk flow. In this experi- 

 ment there was an average reduction of 6.1 per cent from the normal 

 milk flow for a period of five clays following each of the four applica- 

 tions of the arsenical solution. 



Resistance of cattle to infestation by the tick is a variable quality. 

 Of the 10 animals in the tick-infested group, 4 became grossly in- 

 fested; 2 more so than the average, and the remaining 4 but lightly 

 infested. 



The death of cow 15, due to excessive tick infestation, and various 

 recurrences of fever in the other animals, emphasizes the extreme 

 hazard of cattle being continuously subjected to these losses by the 

 tick. Cow 15 was one of the best of the tick-infested group and rep- 

 resented at least a 10 per cent loss from the capital invested in tick- 

 infested cows. Furthermore, the losses observed in this experiment 

 were sustained on rations sufficient to maintain body weights. It is 

 thought that had there been but a scant supply of food, as sometimes 

 occurs when cows are on pasture, the tick-infested cattle would have 

 suffered earlier and probably to a greater degree than they did. The 

 losses in this case were in spite of a good maintenance ration. It is 

 probable that much of the spring losses in cattle now laid to starva- 

 tion, due to lack of pasturage, is materially aided by blood depletion 

 due to ticks, and that repeated dippings would save many cattle 

 otherwise lost. 



These experiments are not extensive enough to furnish an exact 

 measure of the amount of decrease in milk flow due to infestation, but 

 they show that the losses are considerable and vary in immune cows 

 largely hi proportion to the extent of infestation, since in all cases 



