Lactose has been used widely as a semen extender for camels although in the absence of evidence illustrating its suitablility. Considering the osmolarity (316.1 ± 1.48 mOsm/kg) and pH (7.4 ± 0.03) of Bactrian camel semen (Mosaferi S et al. 2004 Theriogenology, in press), the objective of this study was to investigate the effect of osmolarity and pH of lactose extender on the viability of Bactrian camel spermatozoa. In Experiment I, with pH adjusted to 6.9, the effect of lactose concentrations of 9, 10, 11, 12, and 13% with an osmolarity of 290, 333, 350, 376, and 419 mOsm/kg, respectively, on the viability of spermatozoa was investigated. In Experiment II, with lactose fixed at 10%, the effect of extender with pH of 5.9, 6.9, 7.5, 7.9, and 8.9 on the viability of spermatozoa was examined. All extenders contained 20% egg yolk. In both experiments, semen was collected from camels with a sound history of semen quality and fertility (n = 3), using a modified artificial vagina, and divided into different treatments after mechanical removal of semen viscosity (Mosaferi et al. 2004). Progressive forward motility of spermatozoa was examined at the time of semen collection and at 4, 12, and 24 h after incubation at 4°C. Data were analyzed using the GLM procedure in SAS/STAT (SAS Institute, Inc., Cary, NC, USA) after arcsine transformation. At the time of semen dilution, the progressive forward motility of spermatozoa was greater at osmolarity of 290 (28.5%), 333 (34%), and 350 (31%) compared to 376 (13.5%) and 419 (1%) mOsm/kg (P < 0.05). The same trend in the progressive forward motility of spermatozoa was noticed after 4 h of incubation at 4°C; although a significant decrease (P < 0.05) occurred at 290 (11%), 333 (18 %) and 350 (16%). After 12 and 24 h of incubation at 4°C, the progressive forward motility of spermatozoa was less than 10% at 333 and 350 mOsm/kg (P < 0.05). At the time of semen dilution, the progressive forward motility of spermatozoa was greater (P < 0.05) at pH 6.9 (35.5%) and 7.5 (18%) compared to pH 5.9 (0%), 7.9 (7.5%) and 8.9 (2.5%). The same trend in the progressive forward motility of spermatozoa was observed after 4 h incubation at 4°C; although, a significant decrease (P < 0.05) occurred at pH 6.9 (15%) and 7.5 (9%) at this time. After 12 h incubation at 4°C, the progressive forward motility of spermatozoa was less than 5% at pH 6.9 and 7.5 (P < 0.05). In conclusion, 10% (333 mOsm/kg) and 11% (350 mOsm/kg) lactose, at the adjusted pH of 6.9, were the most suitable concentrations of lactose extender for preserving Bactrian camel semen for less than 4 h after which the viability of spermatozoa deteriorated significantly in this extender.

The authors wish to thank the director and station staff of Bactrian Camel Research Center at Jahadabad, Meshkinshahr, Ardabil, for kind provision of facilities and assistance throughout the experiment.