In vitro viability and longevity of cooled Beetal buck spermatozoa extended in skimmed milk and Tris-citric acid based extenders

• Removal of seminal plasma improved the viability and longevity of cooled Beetal buck spermatozoa.
• Viability and longevity of Beetal buck spermatozoa was better in skimmed milk-based extender during cooling up to 72 h.

Two experiments were carried out to improve the quality of cooled Beetal buck spermatozoa stored for 72 h at 4 °C. Effect of seminal plasma (i) on membrane and acrosome integrities, motility and motion characteristics of spermatozoa extended in skimmed milk and Tris-citric acid based extenders (ii) longevity of spermatozoa extended in skimmed milk and Tris-citric acid based extenders were investigated. Semen of 5 Beetal bucks was extended to form 4 treatment groups: i) with seminal plasma in skimmed milk (T1); ii) with seminal plasma in Tris-citric acid (T2); iii) without seminal plasma in skimmed milk (T3); iv) without seminal plasma in Tris-citric acid (T4). Plasma membrane integrity was higher (p < 0.05) in T3 as compared with T2 and T4 at 48 h. There was no effect (p > 0.05) of storage time in T3 on plasma membrane integrity. Acrosome integrity was higher (p < 0.05) in T1 and T3 compared to T2 and T4 at 24 and 72 h. There was no effect (p > 0.05) of storage time in T1 and T3 on acrosome integrity. Progressive motility (%), linearity (%) and beat cross frequency (Hz) were significantly higher in T1 and T3 compared to T2 and T4 from 0 to 72 h. While straightness (%) was significantly higher in T1 and T3 compared to T2 and T4 at 0, 24 and 72 h. Regarding, longevity (% decrease in motion characteristics) of rapid and progressive motile Beetal buck spermatozoa at 72 h storage time, percent decrease in average path velocity, straight line velocity, curvilinear velocity, amplitude of lateral head displacement and beat cross frequency was significantly lower in T3 compared to other three treatment groups. In conclusion, in vitro viability and longevity of cooled Beetal buck spermatozoa was better preserved in T1 and T3 (skimmed milk based extenders with or without seminal plasma) up to 72 h of storage at 4 °C.