MILK-BORNE INFECTIONS 455 



legislation which forces milk from tuberculous cows upon the 

 consumer. 



There are two systems in vogue in different countries for rid- 

 ding herds of tuberculous cattle and at the same time minimizing 

 the temporary losses. The system practised first in Denmark is 

 known as the Bang system. Under this system all animals are 

 tested with tuberculin. Reactors are separated from non-reac- 

 tors by being placed in different stables or in divided stables. The 

 two herds never come in contact with each other and occupy 

 separate pastures when out of doors. All animals with advanced 

 tuberculosis are slaughtered. Calves from infected animals are 

 removed immediately after birth and fed upon pasteurized milk 

 or milk from healthy cows. The calves, -when old enough, are 

 placed with the herd of non-reactors. This herd is then tested 

 every six months and reacting animals removed. Thus a herd 

 free from tuberculosis is raised and the diseased animals gradually 

 eliminated. In the meantime reacting cows are useful for breed- 

 ing purposes and for producing milk to be pasteurized for feeding 

 calves. 



The Ostertag system originated in Germany. This system 

 is based on clinical examination instead of tuberculin testing. 

 All animals showing lesions on clinical examination are slaugh- 

 tered. Calves from all other cows are removed immediately after 

 birth, are kept separate, and are fed on pasteurized milk or on 

 milk from healthy animals. Later they are placed with the 

 other cattle. Clinical examination is repeated frequently. 



While the Bang system eliminates all cows suffering from 

 tuberculosis, no matter how insignificant the lesions, the Ostertag 

 system removes only advanced cases, on the theory that infection 

 is spread chiefly by the latter, and that infection from early cases 

 is so slight as to be negligible. That this theory is correct is by 

 no means generally believed. Animals showing no outward 

 signs of tuberculosis have been known to disseminate tubercle 

 bacilli with their excreta. It happens also that infection of the 

 udder is not recognized for some time, with the result that tubercle 

 bacilli are discharged directly into the milk. The Ostertag sys- 

 tem, therefore, cannot be as successful as the Bang system. 



Both methods entail considerable loss to the herd owner. In 

 Denmark owners are permitted to use milk from reactors with 

 milk from healthy cows, since it is subsequently pasteurized. 

 Only milk for infant feeding is excepted. Also, there are ho 

 restrictions on the selling of infected animals. In countries where 

 such restrictions exist producers suffer great hardships. 



The International Commission for the Control 'of Bovine 

 Tuberculosis recommends the following procedures: 



