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

Abstract

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.