Livability of Bovine Spermatozoa at 5, −25, and −85 C in Tris-Buffered and Citrate-Buffered Yolk-Glycerol Extenders

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Abstract
Survival of bovine spermatozoa in 0.2 and 0.25 [image] Tris-buffered yolk-glycerol (TYG) extenders was generally superior to that in a standard citrate-yolk-glycerol (CYG) extender at 5[degree], -25[degree], and -85oC. The 0.1 and 0.15 [image] Tris-buffered extenders were inferior, P< .01, and the bending of the sperm''s tails in these 2 extenders suggested that these levels of Tris were hypotonic. Twenty ejaculates of semen, averaging 62% motile sperm initially, averaged 50 and 48% after 8 days storage at 5oC in 0.2 [image] and 0.25 [image] TYG, respectively. These same extenders averaged 31% or less motile sperm after one day of storage at -25oC, indicating that this temperature was unsatisfactory for sperm storage with the extenders used. At -85oC, nearly 90% of the sperm motile before freezing were still motile immediately after freezing in 0.2 [image] and 0.25 [image] TYG, but this percentage had dropped to 66% sixty days after freezing. This latter survival rate was higher, P< .05, than that observed in the standard CYG.