Cryopreservation of canine sperm using egg yolk and soy bean based extenders

Animal protein-based extenders are widely used despite being a potential source of bacterial or mycoplasma contamination. Its replacement with vegetal protein-based extenders could represent an interesting alternative for dog sperm cryopreservation. This technique could be further improved by the addition of Tris-Glucose-Citric acid (TGC) that could physically protect the spermatozoa and improve its homeostasis. The aim of this study was to evaluate a cryopreservation protocol for dog spermatozoa using a soybean-based extender (LP1℗) as well as the effects of the addition of (TGC) immediately after the semen collection. Eleven ejaculates from purebred adult dogs were collected, centrifuged in the absence or presence of TGC and processed as fresh or cryopreserved spermatozoa with: egg yolk-based extender (CaniPRO) or LP1℗. Freezing the spermatozoa in LP1℗ reduced the amplitude of the lateral head displacement, the percentage of spermatozoa that showed the intact acrosome and the mitochondrial function (P<0.05). These samples also showed a trend towards increased percentage of apoptotic spermatozoa (P<0.05). The addition of TGC before centrifugation did not improve the seminal parameters and adversely affected motility (P<0.05) in the spermatozoa cryopreserved in CaniPRO. However, TGC did not affect motility and increased (P<0.05) the percentage of intact acrosomes in the spermatozoa cryopreserved in LP1℗, reaching similar values than those cryopreserved in CaniPRO. In conclusion, LP1® plus TGC provide the same level of protection to dog spermatozoa cryopreservation than the egg yolk based extender CaniPRO when comparing standard post-thaw sperm quality parameters.

Effect of cryopreservation on the sperm DNA fragmentation dynamics of the bottlenose dolphin (Tursiops truncatus)

Sperm DNA fragmentation is one of the major causes of infertility; the sperm chromatin dispersion test (SCDt) evaluates this parameter and offers the advantage of species-specific validated protocol and ease of use under field conditions. The main purpose of this study was to evaluate sperm DNA fragmentation dynamics in both fresh and post-thaw bottlenose dolphin sperm using the SCDt following different cryopreservation protocols to gain new information about the post-thaw differential sperm DNA longevity in this species. Fresh and cryopreserved semen samples from five bottlenose dolphins were examined for sperm DNA fragmentation dynamics using the SCDt (Halomax(®)). Sperm DNA fragmentation was assessed immediately at collection and following cryopreservation (T0) and then after 0.5, 1, 4, 8, 24, 48 and 72 h incubation at 37°C. Serially collected ejaculates from four dolphins were frozen using different cryopreservation protocols in a TES-TRIS-fructose buffer (TTF), an egg-yolk-free vegetable lipid LP1 buffer (LP1) and human sperm preservation medium (HSPM). Fresh ejaculated spermatozoa initially showed low levels of DNA fragmentation for up to 48 h. Lower Sperm DNA fragmentation (SDF) was found in the second fresh ejaculate compared to the first when more than one sample was collected on the same day (p < 0.05); this difference was not apparent in any other seminal characteristic. While there was no difference observed in SDF between fresh and frozen-thawed sperm using the different cryopreservation protocols immediately after thawing (T0), frozen-thawed spermatozoa incubated at 37°C showed an increase in the rate of SDF after 24 h. Sperm frozen in the LP1(℗) buffer had higher levels (p < 0.05) of DNA fragmentation after 24- and 48-h incubation than those frozen in TTF or HSPM. No correlation was found between any seminal characteristic and DNA fragmentation in either fresh and/or frozen-thawed samples.