COMPARISONS OF ANTIBIOTIC COMBINATIONS TO CONTROL PSEUDOMONAS-AERUGINOSA IN BOVINE SEMEN

Raw semen experimentally contaminated with 10(6) Pseudomonas aeruginos a calls per milliliter was processed for use in artificial inseminatio n CAI) using three different antibiotic combinations: a) gentamicin, l incomycin, spectinomycin and tylosin (GLST) directly added to contamin ated raw semen followed by dilution with whole milk or egg yolk Tris c ontaining GLST; b) penicillin, streptomycin, lincomycin, spectinomycin and minocycline (PSLSM) in whole milk used to dilute the contaminated raw semen followed by further dilution with glycerolated milk contain ing PSLSM; and c) penicillin, streptomycin, lincomycin and spectinomyc in (PSLS) used with egg yolk Tris diluent in the same way as PSLSM and milk. Diluted Semen was incubated at 35 degrees C for 5 or 40 min bef ore cooling commenced. To assess the efficacy of the antibiotics in co ntrolling P. aeruginosa, diluted Semen samples were cultured for the o rganism before and after freezing, The GLST antibiotics added to raw s emen and milk reduced the Counts of P. aeruginosa before or after free zing. When egg yolk Tris was used, GLST inhibited the organism as indi cated by its low growth in culture before freezing and absence of grow th from samples after freezing. With PSLSM and PSLS treatments, the or ganism was recovered in milk and egg yolk Tris processed semen both be fore and after freezing. However, incubation at 35 degrees C for 40 mi n prior to cooling, compared to incubation of 5 min, appeared to reduc e the bacterial counts after freezing.