Universal Journal of Agricultural Research 1(3): 65-69, 2013 http://www.hrpub.org DOI: 10.13189/ujar.2013.010304 Effect of Different Extenders and Storage Periods on Motility and Fertilization Rate of Rainbow Trout (Oncorhynchus Mykiss) Semen Temel Şahin 1,* , İlker Zeki Kurtoğlu 2 , Fikri Balta 2 1 Recep Tayyip Erdoğan University, Maritime Collegue, Rize, Turkey 2 Recep Tayyip Erdoğan University, Faculty of Fisheries, Rize, Turkey *Corresponding Author: temel.sahin@erdogan.edu.tr Copyright © 2013 Horizon Research Publishing All rights reserved. Abstract The effects of different extenders and storage periods on the motility and fertilization rate of rainbow trout (Oncorhynchus mykiss) semen were evaluated after short-term storage. Semen was collected from anesthetized males by the abdominal massage. After determination of main semen characteristics, the pooled ejaculates were diluted with 4 different extenders at a ratio of 1:3, and stored at 4ºC for 72 h. During preservation, spermatozoa motility (%) were determined every 12 h. Fertilization was carried out using the dry fertilization technique. The sperm-egg ratio was approximately 0.5x106 sperm/egg for optimum fertilization success. The highest motility (64.4±5.27%) and fertilization rate (94.3 ± 0.58 %) were obtained from semen stored with glucose based extender after 72 h storage. These results indicate that glucose based extender is a better preservative than the other solutions used in the study for the short term preservation of rainbow trout semen. Keywords Rainbow Trout, Extender, Semen, Short-Term Storage, Fertility 1. Introduction Preservation of fish sperm for short-term duration is generally useful from the commercial point of view and facilitates various hatchery operations. The short-term storage of sperm at low temperature (4ºC) is mostly applied in short-distance transport of gametes collected in different locations, in synchronizing the timing of obtaining good quality of gamete collection from males and females during artificial insemination, in avoiding the aging of sperm, in facilitating hatchery operations, also in experimental programs for genetic studies [1-3]. The fish sperm could be preserved by storage in undiluted and diluted form. Undiluted sperm stored at low temperature has been reported to cause a reduction in fertilization capacity [4]. Storage of diluted sperm with extender provides better control compared to undiluted storage [5]. Extender solutions can be mixed with semen to increase the volume of the semen samples and to prevent it from deteriorating while it is being held or shipped for insemination. The quality of the stored sperm can be assessed by taking into consideration motility, motility duration, and by its insemination ability [3]. Buyukhatipoglu and Holtz [6] reported that the spermatozoa of rainbow trout were maintained fertilization capacity at 4°C under oxygen and air medium for 15 and 9 days, respectively. Sperm of rainbow trout diluted with ovarian fluid and borax-boric acid buffer and the highest insemination achievement (81.76%) was obtained when ovarian fluid was used as a sperm extender but the spermatozoa demonstrated maximum (34 seconds) forward motility aftcr dilution with borax-boric acid buffer [7]. Bencic et al. [8] suggested that atmospheric air served as a suitable gas for the short-term preservation of salmonid semen. Canyurt et al. [9] indicated that the best results in fertilization and motility were obtained from the sperm samples of rainbow trout diluted with artificial seminal plasma with the rate of 1:1 and stored for 7 days [9]. Hatipoğlu and Akçay [10] found that glucose based extender was a better preservative than Ringer solution for the short term preservation of Abant trout (Salmo trutta abanticus) semen. Niksirat et al. [11] reported that semen samples stored in the absence of antibiotics completely lost fertilizing capacity within 19 days of storage. Şahin et al. [12] clarified that Salmo coruhensis sperm stored in extenders containing glucose, calcium chloride or magnesium chloride remained motile for 24, 14 and 18 days, respectively. As seen in previous studies, despite the use of various diluents to preserve fish sperm without reducing fertilizing capacity, results showed that sperm motility, motility duration, viability and fertilizing capacity vary widely. Individual variation, collecting method and storage conditions affect the success in fish sperm dilution [13]. The goal of this study was to identify the effect of cold storage of