A Preliminary Bacteriological Study of Refrigerated Channel Catfish Sperm

Abstract

Abstract.— This study was designed to simulate conditions encountered routinely during refrigerated storage of channel catfish sperm. Sperm samples were stored at 4 C in non‐sterile and sterile Hanks' balanced salt solution (HBSS). Non‐sterile HBSS was prepared with distilled water stored for 2 wk in a plastic carboy prior to use. Observations were made on the frequency and abundance of bacteria in samples, and on changes in sperm motility and quality. Sperm samples stored in non‐sterile HBSS had a complete loss of motility within 72 h. Samples maintained in sterile HBSS showed an initial decrease in motility between 48 and 72 h, and a complete loss of motility within 10 d. Quality of the sperm in each buffer decreased as motility decreased; morphologic changes and reduced motility of sperm were coincident with increased bacterial numbers. Bacteria were cultured on tryptic soy agar and Pseudomonas F agar (PFA) by spread‐plating 10–μL aliquots from each sample onto bacteriologic media and incubating for 5 d. The dominant bacteria observed were members of the genus Pseudomonas, representing 67% of the total bacteria identified. The dominant pseudomonad (Pseudomonas sp.) cultured from sperm samples stored in sterile buffer produced caseinase, lecithinase, and was β‐hemolytic, whereas the dominant bacteria (P. putida) cultured from samples stored in the non‐sterile buffers did not. Highly motile pseudomonads, present in two samples stored in sterile buffer, colonized below the surface of the PFA media at 4 C. The attributes of the bacterial contaminants that likely contributed to the decrease in sperm quality were production of extracellular enzymes, consumption of oxygen, and a high level of motility. Potential sources of degradative bacteria were commensal flora of channel catfish and the water used in preparing the storage buffer.