74 BULLETIN 1031, U. S. DEPARTMENT OF AGEICULTUEE. 



REDUCTION IN LOSS FROM DISEASES AND PARASITES. 



BlacMeg. — 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 Eange EeserA'e 

 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 v/as started. The Gov- 

 ernment A accine requires rather frec{uent administration, however, 

 and the cost of rounding up and jamiming 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 vaccin*^ has l)een 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 



-•'Calves r> to 20 months of ago arc considered more commonly susc"ptib"e t^ blackle:^, 

 but stock botlL older and younger Ivavc been known to die from the discasa 



