Abstract
The objective of this study was to determine the optimum concentration of egg yolk of free-range chicken as a cryoprotective agent on cyprinid fish, Neolissochilus soroides sperm after 48 h frozen. One level of methanol (10%) combined with six levels of egg yolk solution (0%, 5%, 10%, 15%, 20% and 25%) were tested. Fish Ringer's solution was used as an extender. The diluted sperm was equilibrated for 10 min at 5 °C, then kept at -10 °C temperature for 48 h. Sperm was thawed for 1 min at 40 °C. Spermatozoa viability, abnormality, and fertilization rates were analysed afterwards. The one-way ANOVA showed that the combination methanol with several concentrations of egg yolk solution had a significant effect on spermatozoa viability, abnormality, and fertilization rates (P < 0.05) by improving semen character. The study revealed that the 5% egg yolk solution combined with 10% methanol resulted in the highest rates of viability (82.13 ± 1.75%) and fertility rates (92.96 ± 1.94%), with the lowest abnormality (25.25 ± 2.22%). A 5% egg yolk solution was identified as the best cryoprotective agent for N. soroides spermatozoa preservation at -10 °C for 48 h.
Highlights
God's fish or Kancra, Neolissochilus soroides (Valenciennes, 1842) is one of domesticated fresh water cyprinid fish (Cypriniformes) widely distributed in Southeast Asia including Indonesia (Kottelat et al, 1996)
The sperm quality has decreased gradually depending on the egg yolk solution concentration after 48 h preservation
The ANOVA test showed that the application of egg yolk solution in the diluents gave the significant effect on the sperm viability, abnormality and fertilization rates (P < 0.05)
Summary
God's fish or Kancra, Neolissochilus soroides (Valenciennes, 1842) is one of domesticated fresh water cyprinid fish (Cypriniformes) widely distributed in Southeast Asia including Indonesia (Kottelat et al, 1996). The populations of N. soroides in the wild has been decreasing due to the spawning difficulties (Junior et al, 2005), and overfishing (Rumondang and Mahari, 2017) such has been reported in the previous study in another fresh water fish (Hossain et al, 2015). The preservation of God's fish sperm has not been reported yet
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