576 IOWA DEPARTMENT OP AGRICULTURE 



in order to make serum that is really potent and that will protect a 

 hog from cholera, it is necessary that the strain of disease be bred up 

 to the highest point of virulency. 



This can be done much as corn is bred up. In breeding corn the 

 farmer picks the best ears he can find for planting, he looks for a 

 large ear. With the right color, straight rows, deep kernels, well filled 

 at the end, and one that is well matured. So it is with the disease 

 under the intentions of Dorset, McBride & Niles method. First you 

 use pigs that you know are susceptible for you should know their source, 

 then you use blood from the most virulent strain, for starting the dis- 

 ease, for instance when you kill six or eight a day, you use the blood 

 for starting from the pig that has the disease in the most acute form, 

 one that comes down in the shortest period of time, and the one that 

 shows the best lesions. If they come down in seven or eight days all the 

 better, but if they come down in thirteen or fourteen days the blood 

 should not be used for hyper-immunizing. A pig from four to six 

 months old will produce blood of a more virulent strain than one that 

 is ten or twelve months old. The older pigs seem to acquire more or 

 less natural immunity, therefore it is best to use younger pigs for this 

 purpose. 



This method was only discovered a few years ago by Doctors Dorset, 

 McBride and Niles of the Bureau. At first it was looked upon with 

 considerable suspicion even by the veterinary profession and a very few 

 gave it much thought and study. Only in the last two or three years 

 have the veterinarians realized its value and the importance of this 

 branch of the veterinary practice. To have the best success in using 

 serum it is absolutely necessary that a man take the temperature of 

 all the hogs that one expects to vaccinate even when you do not sus- 

 pect any infection in the herd. 



I have known a number of cases where the veterinarian was called 

 in and although the herd was not believed to be diseased, yet upon 

 examination they have been found to have very high temperature. If 

 these hogs had been vaccinated by the simultaneous method under these 

 conditions the results would have been bad, as the farmers would have 

 claimed that the infection was started' by the vaccination. Where you 

 take the temperature in these herds you will find that some of them have 

 temperatures running from 104 to 106 degrees F. There is no doubt 

 that in some of these cases where the simultaneous method was used 

 in a supposed healthy herd, and where cholera followed, that the in- 

 fection was in the herd at the time of vaccination. The precaution of 

 taking the temperatures would have shown the herd was already in- 

 fected and relieved the veterinarian of this embarrassing position and 

 also maintained the reputation of the serum. 



Where a herd is already infected temperatures should be taken as 

 before stated. Each hog with a normal temperature should be marked 

 with one mark, with a scissor across the back, but where the tempera- 

 ture is above 104 one should place two marks, these marks made with 

 a scissor will last for three or four weeks, which will enable the farmer 

 to keep track of those that were already diseased. 



