PopulaÃÃo bacteriana, motilidade espermÃtica e fertilidade de sÃmen de piracanjuba Brycon orbignyanus, submetido ao resfriamento. / Bacterian population, sperm motility and fertility of piracanjuba semen Brycon orbignyanus (VALENCIENNES, 1849) under refrigeration.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Piracanjuba, Brycon orbignyanus, is a migratory fish species originated from the Grande River basin. Piracanjuba is currently an endangered species. As this species does not breed naturally in captivity, artificial fertilization is necessary. The aim of this study was to improve the protocols for piracanjuba semen refrigeration at 4-6Â C by pH standardization and antibiotic utilization, and to assess, quantitative and qualitatively, the presence of bacterial contamination on the semen. Firstly, sperm motility was evaluated on samples of semen diluted (1:10 total volume) in Saad solution with the pH adjusted to different values â 7.0, 7.6, 8.2, 8.8 â for 7 days. Then, samples diluted in Saad solution pH 7.6 and stored at 4-6ÂC were daily evaluated for sperm motility, and every 48h, for bacterial contamination (CFU/mL) by inoculation on tryptcasein soy agar (TSA), for 8 days. Bacterial colonies of different morphotypes were selected at each counting step, for isolation, selection test (Gram, catalase and oxidase), in vitro sensibility test (antibiogram) with five antibiotics â penicillin, ampicillin, estreptomycin, gentamycin and lincomicin â and frozen for posterior identification. According to the sensibility test, gentamycin was selected, added to Saad solution and used as semen extender. Concentrations of 0 (control), 0.01, 0.1, 0.5 and 1.0 mg of gentamycin per mL of Saad solution were tested. Sperm motility and bacterial growth were evaluated. To check whether gentamycin would interfere with the fertilization process, semen diluted in Saad solution containing the same concentrations tested before, was used to fertilize oocytes. Semen diluted in Saad solution pH 7.6 produced the highest sperm motility during a 7-day refrigeration period. A negative correlation (P<0.01) was observed between sperm motility and bacterial growth, which indicates that the decrease in sperm motility was correlated with the increase in the number of bacteria present in the semen. There was a significant interaction between gentamycin concentrations and refrigeration time, with the highest sperm motility rates being observed after 6 days of storage when gentamycin was added at 0.1mg/mL. This was the lowest concentration able to inhibit bacterial growth in diluted semen and keep the fertilization rates above 80%. Sixty-three bacterial colonies were selected for identification. A large variety of bacterial species was observed and most of the species were rods and Gram negative. Some species commonly observed in mucus of fish surfaces and aquatic environments, such as Aeromonas sp. were also found. Furthermore, a large number of species from the Enterobacteriaceae family (e.g. Citrobacter freundii and Enterobacter sp.), Gram positives, such as Bacillus sp., Enterococcus sp., and coagulase negative Staphilococcus sp., were found. Gentamycin at 0.1 mg/mL produced an inhibitory effect on potentially pathogenic bacteria, which confirms the importance of broad-spectrum antibiotic utilization for the refrigeration of piracanjuba semen.

ASSUNTO(S)

antibiÃticos reproducao animal brycon antibiotic sÃmen brycon resfriamento peixe bactÃrias semen fish refrigerated bacteria

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