Mixed respiratory infections in young cattle is a major cause of economic losses in cattle farming. The existing specific 
prevention and etiotropic treatment measures do not provide radically solving the existing problems. 
Activation  of  interferon  system  is  genetically  determined  reaction  to  viral  infection.  A  disturbance  of  interferon  for-
mation  caused  by  insufficient  interferon  indicating  activity  of  virulent  strains  of  pneumotrophic  virus  ocuurs  in  the 
pathogenesis of ARI diseases which indicates the feasibility of prescribing interferon or its inducers under acute respiratory 
diseases in calves. 
Three groups of calves, 10 animals each, were formed to study the influence of IFN. The first group included clinically 
healthy animals, the third and second ones included animals with clinical features of ARI. The latter were treated according 
to the farm general  scheme of antibiotic intramuscular injection (pharmazyn – 50.1 ml / 10 kg of body weight once a day for 
7 days). In addition, the calves of the third group were treated orally with diaferon. 
It is shown that the inclusion of oral treatments with human recombinant interferon (Diaferon–B) at a dose of 1 IU / kg 
once  a  day  for  3  days  into  the  basic  antibiotic  therapy  of  sick  animals  accelerates  the  regression  of  the  disease  clinical 
manifestations. The therapeutic effect  was combined with the haematological parameters restoration: hemoglobin and red 
blood cells content normalization and the increase in leukocytes phagocytic activity  and serum bactericidal activity. 
A decrease in body temperature, heart rate and respiration movements were observed in the sick animals by the end of 
the experiment. Thus, in the sick animals receiving the basic therapy the body temperature dropped by 1.04 times (p<0.05); 
the heart rate – by 1.4 times (p<0.01), and the frequency of respiration movements – by 1.6 times (p<0.01) respectively. At 
the same time, in the animals additionally treated with interferon, the body temperature decreased by 1.05 times (p<0.01); 

heart rate – by 1.6 times (p<0.001); the frequency of respiratory movements by 1.6 (p<0.01). The results indicate a faster 
regression of clinical manifestation in calves treated with interferon. 
Regression of the disease clinical manifestations in calves on the background of standard treatment supplemented with 
interferon was accompanied with haematological parameters restoration. 
At the beginning of the experiment hemoglobin and red blood cells content in sock calves  was  higher than those in 
clinically healthy animals. Hemoglobin content and erythrocytes number decreased in the course of treatment and the process 
was more active under interferon treatment. 
Decrease in inflammatory processes in respiratory organs of calves occurred against the background of white blood cells 
number decrease. In the  final period (10th day) the amount of these  cells decreased significantly  in groups 2 and 3 – by 
16.5 % (p<0.01) and 16.7 % (p<0.01) respectively and amounted the control level. These changes in leukocitopoesis can be 
explained due to the decrease in the inflammation of the respiratory organs of sick animals. 
Studying the phagocytic activity of white blood cells and serum bactericidal activity revealed that the studied parameters 
decreased at the beginning of the experiment and grew in the course of the treatment. 
Thus,  the  application of  human  interferon  in low  dosis  to  the  mucous  membrane  of  the  mouth  in  calves  under  ARI 
accelerates the regression of the clinical manifestations. 
Prescribing  interferon  in  addition  to  the  conventional  regimen  of  ARI  treatment  in  calf  provides  restoration  of 
hematological parameters. 
Key words: calves, acute respiratory infections, interferon, hemoglobin, erythrocytes, leukocytes.