Effects of Dilution Rate on the Motility and Acrosome Morphology of Boar Spermatozoa Stored at 15 °C

Abstract

Contents: The objective of this investigation was to establish the optimal extent of dilution for storage of boar spermatozoa at 15°C in Kiev diluent. The dilution titers used for the sperm‐rich fraction of ejaculates from 8 boars ranged from 1:2 to 1:50. Seminal doses were stored for 10 days. Motility and acrosome morphology were evaluated after 1, 3, 5, 7, and 10 days of storage. The percentages of motile spermatozoa after 24 and 72 hours of storage were significantly higher for dilution rates between 1:7 and 1:11 than for dilution rates lower than 1:7 or higher than 1:11 (p < 0.05). The percentages of spermatozoa with normal acrosomes after 24, 72, and 120 hours of storage were significantly higher for dilution rates between 1:8 and 1:11 than for dilution rates lower than 1:8 or higher than 1:11 (p < 0.01).

Influence of Boar and Semen Parameters on Motility and Acrosome Integrity in Liquid Boar Semen Stored for Five Days

“…This investigation demonstrates that semen quality was gradually reduced during 102 h of storage, a result which is in compliance with other investigations [15,20]. Even though there was a small but significant reduction in motility at the end of the experimental period, the percentage of motile spermatozoa was maintained at a surprisingly high level even after five days storage.…”

Highlights on Artificial Insemination (AI) Technology in the Pigs

“…The ideal dilution rate of semen with pure electrolyte media ranges between 1:8 and 1:11 for sperm motility and acrosomal integrity. However, dilution titers of 1:9 to 1:11 consistently maintain the highest percentage of sperm motility (74). This is of importance during semen preparation for AI: if the calculated dilution titer lies in the normal range (≥ 1:8 and ≤ 1:11), so extend the semen at the estimated rate; If the calculated dilution titer is below the lower limit (1:8), it is recommended to dilute the semen at 1:8; and If the calculated dilution titer is above the upper limit (1:11), it is recommended to dilute the semen at 1:11.…”

“…The optimum dilution titer differs for e ach semen medium used for sperm preservation. Initial sperm concentration in the ejaculate and characteristics of the medium, such as initial pH, buffering capacity, and osmotic pressure, can inf luence the optimum dilution titer during storage (74). Certainly, a 1:10 dilution of sperm-rich fraction of an ejaculate (probably averaging only 60x10 6 sperm/ml during 13 storage) is not comparable to a 1:10 dilution of the whole ejaculate.…”

“…Furthermore, the lactic acid concentrat ion in a stored sample of semen will be proportional to sperm concentration. Consequently, a medium with a poor buffering capacity requires a higher dilution rate than a medium with a good buffering capacity (74).…”

“…1). Under the practical conditions, high dilution rates are likely to be a problem than low dilution rates, because keeping the entire inseminate dose in one container is less complex than the initial semen storage at a low dilution titer and then addition of the medium just before AI to provide the optimal inseminate volume (2,(74)(75)(76).…”