178 HOG CHOLEEA 



sible risk. In the average farm herd the most 

 opportune time to immunize is three or four weeks 

 after the spring litters are weaned. 



On the other hand, when the herd is immediately 

 threatened with hog cholera we have no choice but 

 to accept it as it is, and protect it at once. Under 

 such circumstances the plan is to give simultane- 

 ous treatment to all animals in condition to re- 

 ceive it, and serum alone to the remainder. Every 

 four weeks we return and repeat the process, con- 

 fining the treatment to those that received serum 

 alone previously, until the entire herd has received 

 simultaneous treatment, and permanent immunity 

 has thus been established. 



When once the adult breeding stock is immune, 

 our task is then to immunize the young litters as 

 they come on. This is relatively simple for the 

 veterinarian and inexpensive for the breeder. 

 On farms where methods of swine husbandry are 

 the best, and at times when there appears to be 

 little immediate danger from hog cholera, the best 

 plan is to keep close watch on the pigs until they 

 are about twelve weeks old and then give simul- 

 taneous treatment. In many herds though, es- 

 pecially the large garbage-fed herds in the East, 

 a high percentage of the pigs will, if left unpro- 

 tected, contract hog cholera before they reach an 

 age approaching twelve weeks, and a considerable 

 number that do not actually contract the disease 



