Cryoprotective and contraceptive properties of egg yolk as an additive in rooster sperm diluents.

The addition of chicken egg yolk to semen extenders is thought to reduce the fertilizing potential of rooster spermatozoa--but not (or at least not as much) that of other avian species. The aim of the present study was to determine whether quail egg yolk, a novel extender additive, provides advantages over chicken egg yolk in the cryopreservation of rooster spermatozoa. Experiments were also performed to determine whether the harmful effect of egg yolk occurs during cryopreservation or during fertilization after artificial insemination. Heterospermic rooster semen samples were divided into aliquots and cooled in a polyvinylpyrrolidone-based medium containing 15% chicken egg yolk, 15% quail egg yolk or no egg yolk at all. The viability of spermatozoa of cooled samples (5 °C) without egg yolk were less viable (P<0.01) than those of samples containing either type of egg yolk. The same aliquots were then cryopreserved for 15 days. Thawed spermatozoa preserved without egg yolk showed lower motility (P<0.001) and viability (P<0.001) than those in samples diluted with either type of egg yolk extender. No eggs were fertilized when hens were inseminated with semen that had been diluted with chicken egg yolk. The fertilization rate was only slightly higher when sperm diluted with quail egg yolk was used (1.5%). The best results were obtained when no egg yolk was used (13.8%). These results show that the addition of egg yolk of either type protects rooster sperm cells against cold shock and during freezing and thawing, but exerts a contraceptive effect in the genital tract of the hen.

Freezability of Iberian ibex (Capra pyrenaica) spermatozoa according to the glycerolization temperature and plasma testosterone concentration.

Ibex spermatozoa can be successfully frozen using glycerolated media. However, no information is available regarding the most effective method of glycerol addition in this species. The aim of the present work was to evaluate the effect of the glycerolization temperature on the response to freezing-thawing of ibex spermatozoa collected by electroejaculation. The effect of the interaction glycerolization temperature x plasma testosterone concentration was also evaluated. The spermatozoa used in this work came from six adult ibexes maintained in captivity. Each ejaculate was divided into two aliquots in a Tris-egg yolk-based medium. One fraction was subjected to single step dilution with 5% glycerol at room temperature (23°C). The other fraction was diluted in two steps, first by dilution at room temperature with an extender identical to that described above but without glycerol, followed by the addition of glycerol after cooling to 5°C. The glycerolization temperature did not affect any sperm variable after thawing. Heterospecific artificial insemination involving domestic goats, revealed no differences in the fertilization rate for frozen-thawed spermatozoa diluted by the one or two step procedures (18.2% vs. 20.0%). The interaction glycerolization temperature x plasma testosterone concentration had no affect on the freezing-thawing of the sperm cells. The results revealed, however, that high plasma testosterone levels during the pre-rutting season may interfere with the freezing-thawing process, having a negative influence on sperm cryosurvival.

Influence of recovery method and microbial contamination on the response to freezing-thawing in ibex (Capra pyrenaica) epididymal spermatozoa.

The method of sperm recovery may influence the initial quality of sperm samples and their response to freezing-thawing. The aim of the present work was to compare two methods for collecting epididymal spermatozoa in order to improve the quality of recovered sperm and reduce possible contamination. Testes were obtained from 23 legally hunted, adult ibex males. The sperm mass of the right epididymis was collected by small longitudinal and transverse cuts made in the cauda epididymidis. The sperm mass of the left epididymis was collected by retrograde flushing from the vas deferens to the cauda epididymidis (using a cannula), employing a Tris, citric acid, glucose, egg yolk-based medium. The flushing method recovered more spermatozoa (P<0.001) than the cutting method. After freezing-thawing, greater acrosomes damage (P<0.001) and more morphological abnormalities (P<0.05) were seen among the sperm cells recovered by the cutting method than among those obtained by retrograde flushing. The method of sperm recovery did not, however, influence the microbial contamination rate. In frozen-thawed samples that were microbially contaminated, motility was significantly reduced (P<0.05) and membrane integrity tended to be poorer (P=0.06). In conclusion, retrograde flushing is recommended for ibex sperm collection since it would appear that microbial contamination is no more of a problem than that encountered with the cutting method, while a larger number of sperm cells more resistant to freezing-thawing can be obtained.

A comparison of the protective action of chicken and quail egg yolk in the cryopreservation of Spanish ibex epididymal spermatozoa.

Egg yolk-based diluents provide adequate cryoprotection for the sperm of several mammalian species. Traditionally, chicken egg yolk has been used as additive for the freeze preservation of spermatozoa because of its wide availability. Variations in the chemical composition of the egg yolk of different avian species appear to influence the protection afforded during cooling, freezing, and thawing. The aim of the present study was to assess the use of quail egg yolk as a novel additive for the epididymal spermatozoa of a threatened wild ruminant species-the Spanish ibex-and to compare its efficacy with chicken egg yolk. Epididymal spermatozoa were diluted using a Tris-citric acid-glucose medium (TCG) composed of 3.8% Tris (w v(-1)), 2.2% citric acid (w v(-1)), 0.6% glucose (w v(-1)), 5% glycerol (v v(-1)), and 6% egg yolk (v v(-1)). Sperm masses from the right epididymes were diluted with TCG-6% chicken egg yolk medium, while those from the left were diluted with TCG-6% quail egg yolk. The thawed spermatozoa preserved with TCG-6% quail egg yolk extender exhibited lower motility (P<0.001), membrane integrity (P<0.001), and viability (P<0.01) than those diluted with the TCG-6% chicken egg yolk extender. The fertility of spermatozoa frozen in TCG-6% chicken egg yolk tended to be higher than in those frozen with TCG-6% quail egg yolk (63.3% vs 36.4%, P=0.19). These results show that quail egg yolk offers no advantages over chicken egg yolk in the cryopreservation of Spanish ibex epididymal spermatozoa.