Search

The retention in blood and the excretion with semen were followed up of tylosin-base, product of the State Economic Corporation "Pharmachim" (People's Republic of Bulgaria). It was found that at muscular application (12 mg/kg) the preparation is resorbed at the site of injection and is retained at a therapeutic level concentration in the blood of rams in the course of 24 to 26 hours. Tylosin gains access to the testes and is excreted with the semen at the same rate as in infectious epididymitis-intact rams. No correlation has been observed between the blood level of tylosin and the content of tylosin in the spermal plasma. The single treatment of rams with tylosin at the dosing cited above is not able to arrest the excretion of Brucella organisms with the semen, and does not improve its morphologic composition.

Studies are the following preparations, produced by "PHARMACHIM": tylosine-base (Tylosine-50), tylosine tartarate (Tylosine pulvis) and tylosine phosphate (substance and granules) and their analogues: tylosine-base (Tylan-50), tylosine tartarate (Tylan soluble) and tylosine phosphate (Tylan AF 99), produced by the "Elanco" Company. The biological activity of the preparation was determined by means of the microbiological method of diffusion in agar. In the case of all experimental treatments, the preparations were compared in conformity with their biological activity expressed in IU/mg of the preparations. The minimum inhibition concentrations of the preparations were determined by the method of serial dilutions in liquid nutritive media on 19 different pathogenic strains. The antispirochetal activity of the preparations compared was tested on 130 cockerels and pullets, experimentally infected with Borrelia anserina of the Surnevo and Pamoukchii serotypes. The application of the preparations started simultaneously with the infection or 24 and 48 hrs after it and continued for days. No significant differences are found in the antibacterial and antispirochetal activities of the Bulgarian tylosine preparations and those manufactured by the "Elanko" Company. The tylosine base does not differ significantly in its antimicrobial and antispirochetal activities from the tylosine phosphate and the tylosine tartarate when equal in IU concentrations and doses are applied.

Experiments were carried out with 4 flocks-a total of 16,940 layers of the White Plymouth Rock breed (10,865 vaccinated and 6075 untreated) and 3000 cocks of the White Cornish breed (502 vaccinated and 1498 untreated). The test birds had been vaccinated at the age of one day. The average month mortality rate among the vaccinated birds was 1.5 per cent, and among the untreated it was 4.9 per cent; for the whole exploitation period these values were 15.35 and 47.17 per cent, respectively. Mortality rate caused by Marek's disease and lymphoid leukosis (specific mortality) in the test groups was 4 times lower as compared with that of the control groups (11.54 as against 44.75 per cent), and the coefficient of epizootiologic effectiveness was 74.4 per cent. Considerable variation was established in the intensity and dynamics of the epizootic process with the vaccinated and unvaccinated birds, on the one hand, and the layers and cocks, on the other. White Cornish cocks proved more resistant to Marek's disease and more sensitive to lymphoid leukosis, while the layers of the White Plymouth Rock breed were more sensitive to Marek's disease and more resistant to lymphoid leukosis. These differences could explain the dynamics peculiarity of the specific mortality exhibited by layers and cocks. The egg-laying capacity of a "forage" layer up to the age of 62 weeks of age in the test flocks was 9.2 (7.2) per cent higher than that of the untreated layers. In exploitation up to the 70th week of age each test layer gave 23 eggs more as compared to the untreated. It is calculated on the basis of the experimental data that a total of 55,200 eggs and more could be obtained from 6000 parental birds vaccinated against Marek's disease during a 10-month laying period.