An Evaluation of Extenders for the Short-Term Storage of Striped Bass Milt

Six extenders were evaluated in two experiments for use in the short-term, refrigerated storage of the milt of striped bass Morone saxatilis. In each experiment, milt samples were collected weekly. The percentage of motile sperm obtained from each extended milt sample and each undiluted milt sample (control) were measured after 1, 2, and 7 d of storage at 3 ± 1°C (mean ± SE). In the first experiment, there were significant changes in the percentage of motile sperm obtained across the spawning season with respect to the day of storage, the extender used, and the day × extender combination. Extender 1 yielded the highest percentage of motile sperm after 2 and 7 d of storage but was not significantly different from extender 4 after 1 d of storage. In the second experiment, two modified versions of extender 1 were compared with the original. Extenders 5 and 6 contained the same ingredients as extender 1 except that their sodium chloride concentrations were increased to obtain osmolalities more closely resembling that of striped bass milt. Extender 6 was closest to the osmolality of striped bass milt and yielded the highest percentage of motile sperm after 2 and 7 d of storage but was not significantly different from extender 5 after 1 d of storage. As in experiment 1, there were significant changes in the percentage of motile sperm obtained across the spawning season with respect to the day of storage, the extender used, and the day × extender combination. Sperm motility in the undiluted control samples and the extended milt samples significantly changed over the course of the spawning season, indicating a seasonal change in milt quality. At the beginning and end of the spawning season, milt quality was low and there was little, if any, significant difference in the performance of the various extenders. In the middle of each spawning season, when milt quality was highest, significant differences in the percentages of motile sperm obtained from the extended samples were evident.