Selection the optimal dose of application associated vaccine against rota-, coronavirus infection and colibacillosis in calves

The main rules for choosing the means of specific prophylactic against colibacillosis (escherichiosis) in cattle is the need to match the antigenic spectrum of the vaccine strains with epizootic strains isolated by diagnostic veteri-nary institutions from pathological material taken from dead calves. Only in this case one should expect high results of the preventive efficacy of the applied vac-cines. The design of vaccines based on pathogenicity factors of bacterias is the most promising direction in the development of new bioproducts of specific pre-vention of infectious diseases of farm animals. Researchs in the areas to choice the optimal doses and ratios of monocompo-nents, determining the optimal immunizing dose, and choosing a adjuvant is an im-portant part of research work on the creation of vaccines. We completed work to establish the optimal dose when using the associated vaccine against rota-, coronavirus infection and colibacillosis of cattle by vaccinat-ing cows in different doses of the test vaccine. Subsequently, serological studies of the blood of animals were carried out, according to the results of which the indica-tors of the best immune response were determined by comparing the established levels of biosynthesis of specific antibodies from animals of the experimental and control groups. A number of indicators of possible reactogenicity of the tested vac-cine were also studied. When conducting studies of blood serum of cows, the indi-rect hemagglutination reaction and agglutination reaction were performed. Serolog-ical blood tests carried out were accompanied by the necessary controls to ensure the reliability of the results. According to the results of studies of blood serum of cows in the experimental groups, immunization of cows with an associated vaccine against rota-, coronavirus infection and colibacillosis of cattle in different volumes led to a significant level of antiviral and antibacterial antibodies. The optimum dose for virus antigens with infectious titres from 7,0 lg and 5,5-TCI50/sm3 for vaccinated cows forms 1,5 sm3 for each viral monocomponents. The optimum dose for each vaccine strains E.coli F4, F5, Аtt25, F41 and 987P forms from 1,5-2,5 milliard bacterial cells for each bacterial monocomponents.