Abstract
The purpose of the present studies was to investigated the actual condition of bacterial contamination of bull semen which was diluted, treated with penicillin and dihydrostreptomycin and stored at low tempreature. A total of 527 semen samples stored in some AI centers was used as material. The results obtained were as follows.
1) In spite of the treatment of with antibiotics, the recovery rate of bacteria from the diluted bull semen was unexpectedly high and increased from 28. 6% in 1957 to 56. 2% in 1961 as shown in Table 1.
2) However the number of bacteria recovered from bull semen treated with antibiotics was much less than that treated with no antibiotics. The number of bacteria in the antibiotics treated semen was also decreased when the semen was collected from the bull in which preputial douche had been performed before semen collection as compared to that without preputial douche (Table 2).
3) From 125 semen samples treated with antibiotics 20 genera (species) of bacteria were recovered, the main ones being Achromobacter, Yeasts, Pseudomonas and Alcaligenes (Table 3). In addition to the 4 genera of bacteria, Escherichia coli and Proteus were also dominant in the semen samples treated with no antibiotics (Table 4). As showen in Table 5, the species of bacteria recovered from the semen was simplified by the treatment with antibiotics. Except Yeasts, these genera of bacteria were generally resistant to penicillin and dihydrostreptomycin, and about 80% of them were Gram negative.
