Characterization of viability, mitochondrial activity, acrosomal integrity and capacitation status in boar sperm...

Extended storage of unfrozen boar semen becomes an alternative because the use of frozen-thawed boar sperm results in low fertility. Sperm viability, mitochondrial activity, capacitation and acrosome integrity of freshly ejaculated boar semen stored in vitro for up to 48 h at 4 degrees C, 15 degrees C, 20 degrees C and 39 degrees C was characterized during the study. The viability of boar sperm was assessed by both Hoechst 33258 and SYBR-14/PI staining. Mitochondrial function was assessed by JC-1 staining. Capacitation status was determined by chlortetracycline (CTC)/Hoechst 33258 staining. The acrosome integrity was analysed with Coomassie blue staining. These data were derived from three ejaculates each from three crossbred boars. The viabilities assessed with SYBR-14/PI, Hoechst 33258 and JC-1 staining correlated highly (r > 0.980). In freshly ejaculated boar semen, 96 +/- 1% of the sperm did not take up the Hoechst 33258, whereas 95 +/- 2% were stained by SYBR-14 and 96 +/- 2% of the sperm had mitochondria exhibiting positive JC-1 staining. Staining with CTC/Hoechst 33258 suggested that a high percentage of sperm became capacitated after 24 h storage at 15 degrees C and 20 degrees C. There were 62 +/- 2% (15 degrees C) and 89 +/- 2% (20 degrees C) capacitated sperm by 48 h. Moreover, most of the capacitated sperm were acrosome intact. These results suggest that SYBR-14/PI, Hoechst 33258 or JC-1 staining can be used to effectively evaluate the quality of boar sperm during in vitro storage.