Using buffered formalin to preserve the bent-tail characteristic of goat spermatozoa for the hypo-osmotic swelling test

The buffered formalin concentration and adding time for the hypo-osmotic swelling (HOS) test in goat semen have never been recommended. This study examined the different buffered concentrations for fixing bent-tail spermatozoa in HOS-treated goat semen for 5-120 minutes. In experiment 1, nine HOS-treated goat semen samples were incubated at 37°C for 60 minutes and bent-tail spermatozoa were evaluated as a control. At the same time, the different final concentrations (0.99, 4.76, 9.09 and 13.04% (v/v)) of buffered formalin were added and compared with the control. In experiment 2, nine HOS-treated goat semen samples were incubated at 37°C for 5, 30, 60, 90 and 120 minutes before being evaluated for bent-tail spermatozoa. At the same time, the different final concentrations (13.04, 16.67 and 20% (v/v)) of buffered formalin were added to the HOS-treated semen. All buffered formalin groups, samples were placed at room temperature for 24 hours before evaluation. The occurrence of bent-tail spermatozoa in the 0.99 and 4.76% (v/v) formalin groups was lower than the control and the 9.09% (v/v) trended to be lower than the control. The 13.04% (v/v) formalin group showed some periods of a decrease in bent-tail spermatozoa. The buffered formalin concentration of at least 16.67% (v/v) added to HOS-treated goat semen had the relative stability of bent-tail spermatozoa for 5-90 minutes and was no different from the non-fixative group. These results recommended the use of an optimal concentration of buffered formalin at 16.67% (v/v) to fix the bent-tail spermatozoa in HOSs-treated goat semen during 5-90 minutes of incubation. This technique will be suitable for goat semen evaluation when there is a short period of incubation.