The optimal divalent cations and storage temperatures for the encapsulation of ram spermatozoa

The aim of this study was to investigate the effects of encapsulation with different divalent cations and temperatures on the quality of ram spermatozoa during cold storage. Experiment 1: diluted semen was allocated randomly into three groups: control, encapsulation with calcium (Ca2+) alginate and encapsulation with barium (Ba2+) alginate. The samples were stored at two different temperatures (4 °C or 16 °C) for 24 h and subsequently examined for spermatozoa quality. Experiment 2: determination of sperm functionality by means of sperm binding was performed. Spermatozoa with and without Ba2+ alginate were cooled for 24 h and then used for sperm binding assay. Experiment 1: the progressive motility of spermatozoa in Ba2+ alginate stored at 16 °C was better than that stored at 4 °C (P = 0.042). Encapsulation with Ba2+ alginate and storage at 16 °C significantly improved progressive motility when compared to Ca2+ alginate (P < 0.001). The motility characteristics of curve velocity, straight linear velocity and amplitude lateral head displacement of Ba2+ alginate at 16 °C were higher than Ca2+ alginate (P = 0.045, P = 0.005 and P = 0.013, respectively). A low storage temperature (4 °C and 16 °C) did not markedly decrease the viability or acrosome integrity of spermatozoa, irrespective the type of crosslinking. Although the spermatozoa released from Ba2+ alginate were motile and could bind to the zona pellucida, the numbers of bound spermatozoa were significantly lower than in the control group (P < 0.001, Experiment 2). In conclusion, Ba2+ alginate is preferable to Ca2+ alginate for the encapsulation of ram spermatozoa with cold storage at 16 °C.