Preservation of the spermatozoa of the dromedary camel (Camelus dromedarius) by chilling and freezing: The effects of cooling time, extender composition and catalase supplementation

Abstract

This study sought to determine the characteristics of dromedary camel sperm following 24 h chilling and cryopreservation, testing two different buffers and cryoprotectants and the presence of catalase (500 IU/mL). Ejaculates were liquefied in Tris-Citric acid-Fructose buffer, and centrifuged through a colloid. For Experiment 1 (n = 5) sperm were cooled 24 h in Green Buffer or INRA-96® containing 0 or 3% glycerol or ethylene glycol. Experiment 2 (n = 5) used the same six treatments to evaluate sperm cryopreserved after 24 h cooling. A test of fertility was run (n = 12 recipients) with split ejaculates of fresh semen cooled 24 h in Green Buffer with and without glycerol. Experiment 3 (n = 7) cryopreserved sperm cooled 2 and 24 h in Green Buffer without cryoprotectant and with and without catalase. Sperm parameters measured before and after treatments included motility, viability and acrosome integrity. Experiment 1 showed no reduction in all sperm parameters after 24 h and no differences between buffers or presence or not of either cryoprotectant. Experiment 2 showed Green Buffer to be better than INRA for supporting sperm frozen after 24 h cooling while, for both buffers, there were few differences in sperm parameters if cryoprotectant was present or absent. Pregnancies were confirmed in 4/6 animals (67%) while no recipients receiving sperm chilled with glycerol were pregnant. In Experiment 3, catalase-supplemented sperm had maintained better motility 2 h post thaw; there were no differences between 2 or 24 h cooled sperm parameters for presence or absence of catalase. There was neither advantage nor disadvantage to coooling sperm 24 h prior to cryopreservation. We concluded that dromedary sperm can be chilled (24 h) and then either inseminated or cryopreserved. While glycerol presence in Green Buffer during chilling did not interfere with cryosurvival it may be toxic to the fertility of fresh chilled sperm. Catalase supplementation during cooling helps maintain sperm motility post thaw.