74 BULLETIN 1031, U. S. DEPARTMENT OF AGRICULTURE. 
REDUCTION IN LOSS FROM DISEASES AND PARASITES. 
Blackleg.—In the past blackleg has been the main cause of losses 
from disease. In May, 1915, for example, 50 head of yearling steers 
died of blackleg in one herd of about 1,000 head. All yearlings were 
vaccinated immediately and losses stopped. Systematic vaccination 
of all stock between the approximate ages of 5 months and 20 months 
was started in the fall of 1915, and has been continued since. 
The, Government blackleg vaccine was used the first two years, 
with special care to secure proper preparation and administration. 
All stock of the more susceptible age °?* were vaccinated twice and 
sometimes three times a year, usually during fall branding and once 
or twice in the spring. The experience with the Government vaccine 
has been that a high per cent of immunity resulted from vaccination, 
but that the period of immunity was short, usually from 3 to 6 
months. 
The loss attributed to blackleg on the Jornada Range Reserve 
among calves vaccinated with the Government vaccine in 1916 and 
again in 1917 was approximately 1 per cent for stock 5 to 20 months 
of age. These results are very good as compared with the 5 per cent 
loss in one month in 1915, before vaccination was started. The Gov- 
ernment vaccine requires rather frequent administration, however, 
and the cost of rounding up and jamming the cattle incident to vac- 
cination two or three times a year is no small item. 
Since the fall of 1917, all calves have been vaccinated with a 
germ-free serum developed at the experiment station of the Kansas 
Agricultural College. This vaccine has been administered to calves 
4 to 5 months of age and up, during fall branding and during wean- 
ing time in winter. Each calf vaccinated is marked by “ bushing” 
its tail to distinguish it from those that have not been vaccinated. 
Where calves are not weaned but left on the range good results have 
been obtained by working the stock at watering places for several 
days, vaccinating the calves and yearlings and turning them back on 
the range. 
Since 1917, in so far is it has been possible to determine, no calves 
or yearlings treated with this vaccine have died from blackleg. <A 
few losses attributed to blackleg occurred when the work was de- 
layed and some calves reached the susceptible age before being 
vaccinated. Undoubtedly some deaths occurred also among calves 
that were missed. The loss from this disease has been reduced to 
less than 0.1 per cent of stock of susceptible age with the use of 
the improved vaccine. 
Systematic vaccination is possible under open-range conditions, 
and the good results obtained from both the Government vaccine and 
24 Calves 5 to 20 months of age are considered more commonly susceptible to blackleg, 
but stock both older and younger have been known to die from the disease, 
