ECONOMIC IMPORTANCE AND ETIOLOGY 15 



of the greatest importance, as it usuall}' attacks cows, 

 and causes death just at the time when they should be 

 at their highest value — i.e., after the second calf — when 

 giving the best yield of milk. We have seen valuable 

 three-year-old Jersey cows dying of this disease within 

 a few weeks of calving, and a pedigree bull on the 

 same farm reduced in value in the course of twelve 

 months from over ;^ioo to thirty shillings. 



The loss sustained by an owner who attempts to 

 treat the disease wnth extra food and drugs is fourfold ; 

 there is no return for the extra expense in feeding; 

 there is less milk; a poor, weakly, or dead calf; and 

 when in the end the animal is sent to the butcher a 

 very low price is obtained. In the worst cases the 

 animals are sent to the nearest kennels, or are buried 

 on the farm. Besides these losses, there is the con- 

 stant danger that healthy animals on the same land or 

 in the same byre will become infected, and the loss is 

 likely to become an annual one. The same may be 

 said to hold good for tuberculosis in cattle ; but while 

 it is possible for a cow extensively affected with tuber- 

 culosis to be in fairly good condition, it is rare to find 

 an animal badly affected with Johne's disease which is 

 not so emaciated as to be wholly condemned in a 

 properly inspected meat market. 



A farmer who buys a good and recently calved dairy 

 cow at the average price of ;^2o, and only obtains 

 250 gallons of milk instead of 500 to 600, loses on the 

 milk alone about £6. At the end of a year, in the case 

 of a sound animal, he would expect to have a cow 

 worth about £ig, and a calf worth at least ^1 ; but if 

 the animal be badly affected with Johne's disease, he 

 would be fortunate in obtaining ;^5, so that a loss of 

 ;^2o is not an excessive estimate, as the milk has only 

 been calculated at 6d. a gallon. 



