170 ILLINOIS STATE DAIRYMEN'S ASSOCIATION 



as a check test and has revealed a considerable number of 

 cases of tuberculosis which had escaped other methods of 

 diagnosis. In its application a disk containing the diag- 

 nostic tuberculin is placed in the eye of the animal. If the 

 animal is not diseased no disturbance is indicated, but if 

 infection exists there follows a characteristic formation of 

 pus in the treated eye. 



A problem of considerable importance is the tubercu- 

 lin testing of cattle at public stockyards. Such testing is 

 aimed to check traffic in diseased animals and to protect 

 communities which have little bovine tuberculosis from in- 

 fection by cattle that are diseased or of doubtful health. 

 This condition applies especially to dairy stock and to 

 breeding cattle, but in preventing interstate movement of 

 tuberculous animals live-stock sanitary officials recognize 

 the need for doing the work in the most expeditious manner. 



Benefits Derived from Tuberculosis-free Herds. 



Many inquiries have been made with a view to obtain- 

 ing reliable information as to the comparative value of cat- 

 tle known to be free from tuberculosis and those the health 

 of which is not definitely known. Many breeders and live- 

 stock owners will not introduce animals into their herds un- 

 less they are reasonably certain that no tuberculosis exists 

 in the herds from which the animals are taken. To such 

 owners an animal of doubtful health has no intrinsic value 

 and they will readily pay a premium for animals from ac- 

 credited herds. For grade cattle $10 per head is a con- 

 servative estimate of the premium on animals known to be 

 free from tuberculosis, and $25 per animal is likewise a 

 reasonable estimate of the premium on purebred cattle. 

 When these figures are applied to the total number of dairy 

 and beef creeding cattle in the United States the reader will 

 recognize the enormous toll imposed by this insidious dis- 

 ease. 



It is reasonable to expect that within a few years 

 American breeders will be selling for export many more 

 breeding animals than are being exported at the present 

 time. The degree of success to be attained in the future 





