Nc 7. DEPARTMENT OF AGRICULTURE. 17? 



if injected with a regular dose of the same. It is the owner's desire 

 to have his main milking herd known as one that contains no tubercu- 

 lin reacting animals. This is also a regulation of some of the larger 

 cities in which the milk is sold. • 



To briefly summarize, we find that since llJOl we have vaccinated 

 184 calves, of which forty-six are in the main milking herd at the 

 present time. Of the 143 animals that were sold for breeding pur- 

 poses, for beef or that died from lung worms, etc., post-mortem ex- 

 aminations were obtained on approximately 100 head and no lesions 

 of tuberculosis were found in any except those aformentioned follow- 

 ing the tuberculin test of 1911. 



There were no calves vaccinated that were born in the year 1910 

 and 1911, as most of these calves the owner desired to sell to parties 

 in either his own State or in other states. It has been found that 

 animals receiving tuberculosis A^accine will react to tuberculin for a 

 certain length of time following the final vaccination. This reaction 

 to tuberculin interferes with interstate shipments and for this rea- 

 son the vaccinations were discontinued for the period aforementioned, 

 but it is my intention to vaccinate all calves this Fall that have been 

 born during the summer months and are desired for future members 

 of the herd. This decision has been brought about by the fact a few 

 months ago a lot of fourteen calves that were stabled in a barn which 

 had been previously used to keep reacting animals in, seemed to be 

 unthrifty. One of these calves died from some unknown cause, and 

 upon postmortem examination a suspicious lymphatic gland was 

 found. Upon section it showed no distinct tubercle formation but 

 was sent to John Hopkins University for miscroscopic examination 

 and tubercle bacilli were found in the smears made from the same. 

 This stable before the ca^lves were placed therein had been thoroughly 

 disinfected. In order to determine the extent of infection of this 

 los of animals, six of the others were killed after having given posi- 

 tive tuberculin reactions, and upon autopsy showed incipient active 

 foci of tuberculosis. These animals had not received any tubercu- 

 losis vaccine. The remaining animals of this lot which did not react 

 to tuberculin will be carefully watched and not allowed to mingle 

 with other members of the herd until they have given another nega- 

 tive tuberculin test. 



It is of interest to know that this particular lot of calves were 

 taken care of by the same party who had charge of the two cows afore- 

 mentioned, that is Proceda and Francelraar which were killed npon 

 physical examination. This may have been the source of infection 

 of this lot of calves. 



It is my belief that if these animals had been vaccinated with 

 tuberculosis vaccine within eight or ten weeks following their birth, 

 they would have had sufficient resistance to withstand the slight 

 infection to which they were subsequently exposed. 



Vaccinated animals have been tuberculin tested at intervals of one 

 month from the third month to the twenty-fourth month following 

 the final vaccinations in order to determine at what period they lose 

 their sensitiveness to tuberculin. The time when the sensitiveness 

 is lost has been found to be rather irregular, varying from six months 

 to nineteen months. It is my belief, however, that the sensitiveness 



12—7—1910 



