Research on epizootiology of enzootic bovine leukosis under the conditions of natural infection on the state-owned farms [in Bosnia and Herzegovina (Yugoslavia)]
1989
Ivacic, Z. (Ujedinjena poljoprivreda, promet i industrija "UPI", Sarajevo (Yugoslavia))
The research on epizootiology of enzootic bovine leukosis (EBL) was carried out on 7 state-owned farms in Bosnia-Herzegovina, (Yugoslavia) on animals of Holstein-Friesian, East-Friesian and Symenthal breed, aged 1-12 years. Spread of infection within the affected farms occurred through various routes, both vertically and horizontally. On 4 leukosis infected farms percentage of affected animals ranged from 1.52% to 19.63%. The average for the leukotic farms over the 5 year period under investigation was 14.66%. Vertical transfer of infection was established for only 6.28% of leukosis affected breeding animals; on this finding the author has based the confirmation of the knowledge that horizontal route of infection with leukosis is the predominant one. With regard to the age of the affected animals, the largest number of leukotic animals was found in the 3-7 year age group, in which 5-year old animals had the highest percentage of leukosis cases. Of the total number of leukotic animals in lactation, infected were 23.19% of the cows on the farms producing average quantity of milk; 58.82% cows on the farms producing above average quantities of milk, and only 17.99% cows on the infected farms whose production was under the average.
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