Freezability of Thai Native Crossbred Horse Semen in Different Extenders

Abstract

The aim of this study was to investigate the freezability of Thai native crossbred (T) and purebred horse (F) sperm using different extenders. Semen samples were collected monthly from five T and four F stallions between 5 and 12 years of age. The extenders used were INRA-Y (E1), INRA-Y supplemented with 50 mM L-glutamine (E2), lactose-EDTA (E3) and lactose-EDTA supplemented with 50 mM L-glutamine (E4). Sperm motility, membrane integrity and acrosome integrity were assessed in fresh and frozen samples by computer- assisted sperm analyses (CASA; IVOS, Hamilton Thorne), HOS tests and combined FITC-PNA and PI techniques respectively. Total motility and progressive motility of post-thaw T semen were significantly higher in E3. However, no significant differences between intact membrane-acrosome and positive membrane integrity of post-thaw T semen were observed between extenders. All characteristics of post-thawed semen in extenders supple- mented with 50 mM L-glutamine tended to be lower than those without L-glutamine, and semen from one F and two T stallions could be used for cryopreservation. In conclusion, semen from T and F stallions in our study displayed poor overall freezability. Cryopreservation of stallion semen in lactose-EDTA with 4% glycerol exhibited better post-thaw semen quality. Supplementing glutamine to extenders did not produce beneficial effects on any post-thaw semen parameters examined due to poor initial freezability.