In recent years, there has been an increased interest in the sperm preservation and maintenance of genetic resources of small ruminants. The study aimed to determine and compare the preservation effects of skim milk and Tris-citrate on the quality of chilled and frozen-thawed indigenous ram semen (n=13) during rainy monsoon season (June to October) in Bangladesh. Semen was collected from four indigenous rams by artificial vagina method to observe motility, viability and membrane integrity at 0, 24, 48, 72 hrs of storage. The hypo-osmotic resistance test (HOST) was used to evaluate the sperm membrane integrity. The ejaculates were divided into two groups according to dilution with skim milk or Tris-citric acid egg yolk media for chilling and freezing. Motility, viability and membrane integrity were significantly (p<0.01) higher in chilled semen samples diluted with skim milk in comparison to those of semen diluted with Tris-based extender at all time-based observations. However, around 50% motility was preserved up to 48 hours by both extenders. Results also showed that motility, viability and HOST (+ve %) decreased drastically after cryopreservation irrespective of diluents. Similar to chilled semen, studied parameters were significantly higher (p<0.05) in frozen-thawed semen diluted with skim milk based extender, though quality parameter of frozen-thawed semen was not satisfactory. In conclusion, skim milk based extender appears to be a better option compared to Tris based extenders for chilling semen of indigenous ram up to 48 hours with acceptable quality. Whether the differences found between the extenders will be reflected in the fertility results after artificial insemination (AI) is yet unknown and needs to be further studied.
Indigenous ram semen; skim milk; Tris-citrate; motility; viability; HOST.
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