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A Tris-based extender (SHOTOR diluent) has been developed for preserving Bactrian camel semen at 4�C (Niasari-Naslaji et al. 2005 Reprod. Fertil. Dev. 17, 198 (abstr.)). The present study investigated the possibility of utilizing the SHOTOR diluent for the cryopreservation of Bactrian camel semen. A modified bovine artificial vagina (Masaferi et al. 2005 Theriogeology 63, 92-101) was used to collect semen from three fertile bulls. The viscosity of the semen was reduced mechanically (Mosateri et al. 2005) and the homogenized semen was divided equally into two parts. Each part was sequentially diluted with either IMV buffers (Green buffer: first extender; White buffer: second extender; IMV, France) or SHOTOR diluents (without glycerol: first extender; with 12% glycerol: second extender). SHOTOR diluent consists of 2.6 g TIS, 1.35 g citric acid, 1.2 g glucose, and 0.9 g fructose in 100 mL of deionized water, with an osmolality of 330 mOsm/kg and pH of 6.9. All extenders had 20% egg yolk and antibiotics. The semen was diluted at the ratio of 1:1 with the first extender. The diluted semen was then cooled within 2 h to 4�C. At this temperature, the second extender was added at the same volume as the diluted semen in three steps with an equal volume, 10 min apart. After a 30-min equilibration time, beginning after addition of the last fraction of the second extender, the diluted semen was loaded into 0.5-mL straws at a concentration of 50 _ 106 sperm per straw. The straws were maintained for 20 min at 4 cm above the liquid nitrogen surface, after which they were plunged into liquid nitrogen. The semen was thawed at 40�C water bath for 20 s. Progressive forward motility of spermatozoa was assessed at the time of dilution and immediately after thawing of the semen. The experiment was replicated four times. Data were analyzed using GLM procedure in SAS/STAT after arcsine transformation. At the time of dilution, there was no significant difference in progressive forward motility of spermatozoa between IMV buffers (51.8%) and SHOTOR diluent (61%; P > 0.05). However, after thawing, there was a significant decrease in progressive forward motility of spermatozoa in IMV buffers (4.2%) compared to SHOTOR diluent (29.9%, P < 0.05). In conclusion, in this experiment, SHOTOR diluent was more efficient for cryopreserving Bactrian camel semen than IMV extender. Shotor means camel in the Persian language. |
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