22 



FARMERS' BULLETIN 834. 



only a moderate quan- 

 tity of light feed 

 should be given to the 

 hogs, and thereafter 

 they should be re- 

 turned to full feed 

 and whole grain 

 .very gradually. 



SERUM-ALONE INOCU- 

 LATION. 



The serum -a lone in- 

 oculation consists 

 merely in injecting, 

 in the manner just 

 described, the serum 

 which is obtained 

 from hyper - immu- 

 nized hogs. The se- 

 r u m may be used 

 either to immunize 

 healthy hogs or to 

 treat those that are 

 sick of cholera. Good 

 serum, properly ad- 

 ministered, is incapable of causing any harm to the treated animals. 

 It does not contain the germs of hog cholera and therefore can not 

 start an outbreak of cholera, even when the methods of application 

 are faulty or the serum is of low potency. It is in the safety of 

 this method of treatment that its chief advantage lies. 



This method is always to be recommended in preference to any 

 other for treating sick hogs. Unfortunately, in healthy hogs not 

 infected with cholera it does not produce a permanent protection. 

 If it did it would certainly be the only method to be recommended. 

 The length of protection which follows the injection of serum alone 

 seems to depend to a certain extent upon the peculiarities of indi- 

 vidual hogs, which can not be determined beforehand, and also to 

 some extent upon the dose of serum. Certain experiments have 

 indicated that the immunity lasts somewhat longer in hogs which 

 receive exceptionally large doses. Ordinarily a farmer may count 

 upon the immunity lasting at least 3 or 4 weeks following the treat- 

 ment of healthy hogs with serum alone. This immunity seems to 

 last longer in old hogs than in young pigs. In some cases it appar- 

 ently produces immunity which lasts for 2 or 3 months. At times, 

 when healthy hogs are treated with serum alone and shortly there- 



Fig. 10. — Flank injection. 



