The effect of cold shock and deep-freezing on ram spermatozoa collected by electrical ejaculation and by an artificial vagina

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Abstract
Spermatozoa collected with an artificial vagina (AV) were more resistant to cold shock as judged by motility and staining reaction than when ejaculated electrically (EE). Dilution of AV spermatozoa in AV seminal plasma caused some increase in susceptibility to cold shock, particularly as judged by motility scores, but the evidence suggests that EE seminal plasma renders spermatozoa more susceptible than does AV seminal plasma. Spermatozoa exposed to cold shock immediately after collection were most permeable to Congo red and became increasingly impermeable when incubated at 30°C; the increase in resistance of AV spermatozoa was greater than that of EE spermatozoa. When 10 successive ejaculates were collected from rams by the artificial vagina there was no great change in volume but the spermatozoal concentration declined. After cold shock, the percentage of unstained spermatozoa fell to very low levels by the fifth ejaculate and there was also a decline in motility. The viability of semen thawed after freezing to –79°C by rapid freezing method was better than when a slow freezing method was used, particularly when the semen was collected with an artificial vagina.