114 DAIRY CATTLE AND MILK PRODUCTION 



Guarding against Disease. The only diseases that are 

 likely to be brought into a herd by the purchase of animals 

 are tuberculosis and contagious abortion, and these should 

 be guarded against with the greatest care. 



Tuberculosis does not develop spontaneously. It spreads 

 only by the transmission of the germs which cause it from an 

 infected animal. A cow may be badly affected with the dis- 

 ease without showing any evidence of the fact. The placing 

 of such an animal with a healthy herd may result in the entire 

 number contracting the disease within a few months. For- 

 tunately the tuberculin test makes it possible to determine 

 accurately whether an animal is infected. In starting a dairy 

 herd every animal should be subjected to the tuberculin test 

 by a competent person, and rejected unless sound. If this is 

 done, and every animal that is added to the herd later is tested 

 before being placed with the others, this dangerous disease 

 may be excluded indefinitely. Failure to observe this pre- 

 caution has resulted in many cases in the infection and loss of 

 valuable herds. 



It is a more difficult matter to guard against contagious 

 abortion, and the financial losses resulting from it are severe. 

 There is no means of testing a cow to learn if she carries the 

 disease. All that can be done is to make careful inquiry re- 

 garding the health of the herd from which it is desired to pur- 

 chase stock. It should be understood that the bull as well 

 as the cows may carry the germs of this disease. 



As a rule it is much safer to purchase stock from a breeder 

 than from a dealer, since in the latter case little or no 

 information is usually available regarding the dairy qualities 

 of the cows or as to the health conditions in the herds from 

 which the animals originally came. Further, animals in the 



