EFFECTS OF EQUEX STM PASTE ON VIABILITY OF FROZEN-THAWED DOG SPERMATOZOA DURING IN-VITRO INCUBATION AT 38-DEGREES-C

In the canine, artificial insemination with cryopreserved semen genera lly yields lower pregnancy rates with vaginal deposition than with ute rine deposition, one of the reasons being the shortened life span of f rozen-thawed spermatozoa. The incubation of spermatozoa at body temper ature partially mimics the situation in vivo, and evaluation of the ki netics of viability loss under these conditions can be used to measure the damage caused by freezing and thawing procedures. In this study, 2 aliquots were separated from split ejaculates collected from 7 dogs and were frozen by lowering the straws, in 3 steps, into an LN(2) tank after dilution with egg yolk Tris-citrate-glucose extender with or wi thout the addition of 0.5% Equex STM paste. Motility and plasma membra ne integrity (evaluated with the combined fluorescent probes 6-carboxy fluorescein diacetate and propidium iodide) were assessed immediately after thawing and over the next 3 h at 38 degrees C. The addition of E quex STM paste significantly increased the proportion of spermatozoa h aving an intact plasmalemma immediately after thawing compared with th e control. It also increased the longevity of the thawed spermatozoa, prolonging the maintenance of both motility and plasma membrane integr ity. (C) 1997 by Elsevier Science Inc.