The effect of different extenders on post-thaw sperm survival, acrosomal integrity and longevity in cryopreserved semen of Formosan Sika deer and Formosan Sambar deer

Abstract

This study investigates the efficacy of five extenders in contributing to the outcome of semen cryopreservation in Formosan Sika and Sambar deer. Pooled semen ( n=4) of six males of each breed was used. In Sika deer, semen collection rate was 96% (23/24) over all electro-ejaculations. Volume, sperm motility and sperm concentration of fresh ejaculates was 0.5±0.4 ml, 77±6% and 1471.3±940.0×10 6 ml −1, respectively. Post-thaw motility in respective extender was A: 66±16%; B: 71±2%; C: 73±6%; D: 9±4% and E: 26±12% (mean±S.D.). In extender C (74±14%) more viable spermatozoa were preserved than in the others (A: 64±10%; B: 48±11%; D: 41±16%; E: 47±6%; P<0.05). Acrosomal integrity was not influenced by extender composition. Post-thaw motility did not decrease during a 4-h incubation period, irrespective of the extender used ( P>0.05). In Sambar deer, semen collection rate was 88% (21/24) over all electro-ejaculations. Volume, sperm motility and sperm concentration of fresh ejaculates was 1.3±0.5 ml, 82±4% and 379.1±252.2×10 6 ml −1, respectively. Post-thaw motility was in respective extenders A: 69±2%; B: 74±6%; C: 73±2%; D: 13±6% and E: 31±20%. Extenders B and C were superior ( P>0.05) with respect to sperm motility. Similarly, post-thaw viability in extenders A (70±7%), B (76±7%) and C (79±2%) was higher than that D (25±19%) and E (29±17%) ( P<0.01). Sperm acrosomal integrity was better preserved in extenders B (86±4%) and C (83±4%) than in extenders A (54±13%), D (39±22%) and E (46±22%) ( P<0.05). Post-thaw sperm longevity in extender A reduced from 69 to 16% during incubation ( P<0.05) whereas only a slight decrease was observed in the other extenders after 4 h. In conclusion these data show that egg-yolk–Tris–Tes–glycerol based extender C containing Equex STM paste is optimal for freezing semen of Formosan Sika deer while egg-yolk–Tris–citric acid–glycerol based extender B containing Equex and extender C are superior in semen cryopreservation to others for Formosan Sambar deer.