Effects on the quality of frozen-thawed alpaca (Lama pacos) semen using two different cryoprotectants and extenders

摘要

Aim: To evaluate two extenders and two cryoprotectant agents (CPA) for alpaca semen cryopreservation. Methods: Semen samples were obtained from four adult alpacas (Lama pacos) and frozen using extender Ⅰ (TRIS, citrate, egg yolk and glucose) or extender Ⅱ (skim milk, egg yolk and fructose), each containing either glycerol (G) or ethylene glycol (EG) as CPA. Consequently, four groups were formed: 1) extender Ⅰ-G; 2) extender Ⅰ-EG; 3) extender Ⅱ-G; and 4) extender Ⅱ-EG. Semen was diluted in a two-step process: for cooling to 5℃ (extenders without CPA), and for freezing (extenders with CPA). Viability and acrosome integrity were assessed using trypan blue and Giemsa stains. Results: When compared, the motility after thawing was higher (P < 0.05) in groups Ⅱ-EG (20.0% ± 6.7%) and Ⅱ-G (15.3% ± 4.1%) than that in groups Ⅰ-G (4.0% ± 1.1%) and Ⅰ-EG (1.0% ± 1.4%). Viable spermatozoa with intact acrosomes in groups Ⅱ-EG (18.7% ± 2.9%) and Ⅱ-G (12.7% ± 5.9%) were higher than that in groups Ⅰ-G (5.7% ± 1.5%) and Ⅰ-EG (4.0% ± 1.0%). Conclusion: The skim milk- and egg yolk-based extenders containing ethylene glycol or glycerol to freeze alpaca semen seems to promote the survival of more sperm cells with intact acrosomes than the other extenders.