A simple and fast alternative method to remove glycerol from chicken semen after cryopreservation

Glycerol is not suitable for the cryopreservation of quail semen

1. This study investigated the potential use of glycerol as a cryoprotectant for quail sperm cells. Its role in maintaining sperm fertilising ability in vivo and in vitro quality parameters, such as motility, was assessed.2. The data showed that the presence of glycerol in semen samples was associated with infertility, which suggested that removal prior to insemination is mandatory. Removal through serial dilution centrifugation was associated with fewer than 5% of motile sperm cells and resulted in no fertility.3. In conclusion, glycerol alone is not suitable for quail semen cryopreservation, and other approaches need to be investigated to develop cryobanking programmes for this species.

Metabolites assay offers potential solution to improve the rooster semen cryopreservation

Semen cryopreservation represents a promising technology utilized for preserving high-quality chicken varieties in husbandry practices. However, the efficacy of this methodology is significantly impeded by the diminished quality of sperm. Metabolites, as the end products of metabolic reactions, serve as indicators of biological processes and offer insights into physiological conditions. In this study, we investigaged the sperm quality and alteration in metabolic profiles during the cryopreservation of Longyou Partridge Chicken semen. Following artificial semen collection, four groups of semen samples were established based on four points of the cryopreservation process (Ⅰ, fresh semen; Ⅱ, semen added extender and chilled at 4 °C for 30 min; Ⅲ, semen added cryoprotectants; Ⅳ, semen gradient freezed and stored in liquid nitrogen). Semen cryopreservation has a negative effect on the percentage of sperm in a straight-line trajectory (LIN), has no significant effect on total motile sperms (TM) or the proportion of sperm with typical morphology (NM). Metabolites were identified using LC-MS technique and analyses including Principal Component Analysis (PCA), Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA), Univariate statistical analysis, and the Kyoto Encyclopedia of Genes and Genomes (KEGG) database were employed to identify metabolites. A total of 2471 metabolites had been identified, with the majority of the list being made up of amino acids and their metabolites as well as benzene and substituted derivatives. Group II exhibits 882 metabolites with significantly elevated abundance relative to Group I, alongside 37 metabolites displaying decreased abundance. In Group III, 836 metabolites demonstrate notably augmented abundance compared to Group II, while 87 metabolites exhibit reduced abundance. Furthermore, Group IV showcases 513 metabolites with markedly heightened abundance in comparison to Group III, and 396 metabolites with decreased abundance. Specific metabolites such as 5-Hydroxylysine, Phosphocholine, and alpha-d-glucose-6-phosphate exhibited a progressive decline during the cryopreservation process, correlating with either dilution and chilling, cryoprotectant addition, or freezing. In conclusion, our investigation systematically examined the changes of seminal metabolome and sperm quality throughout the cryopreservation process of rooster semen.

Exploring how sucrose-colloid selection improves the fertilizing ability of chicken sperm after cryopreservation with glycerol

Currently, glycerol is the most effective cryoprotectant when combined with straw packaging for preserving chicken sperm. Glycerol, however, has toxic effects on sperm cells, which can reduce fertility when present in inseminated semen. Historically, the serial dilution (SD) method was developed to eliminate glycerol and mitigate its adverse effects. We have recently developed a new method for removing glycerol called sucrose-Percoll (SP), that can be performed at either 4°C (4°C-SP) or 20°C (20°C-SP). This SP protocol has been found to be simpler and faster to improve fertility compared to the traditional SD method. Nevertheless, the reasons for such effectiveness differences between glycerol removal procedures remained unclear and required more comprehensive understandings for future protocol developments. Here, we examined the effects of SP and SD protocols on the fertility duration. We also investigated the potential causes of varying effects of these methods by analyzing sperm quality parameters and sperm storage in the hen's reproductive tract. The fertility was significantly higher in 4°C-SP than 20°C-SP during the first 6 d after insemination, and also higher than sperm processed using SD. No difference was observed between 20°C-SP and SD between 7 and 13 d. However, a 2.7-time higher fertility was shown with 4°C-SP. In addition, the SP method demonstrated a 2-fold greater ability to remove glycerol than the SD method. Sperm centrifuged at 4°C-SP exhibited higher sperm storage compared to 20°C-SP and were higher than sperm treated with SD. Overall, our findings revealed that the differences in efficiencies between SP and SD methods were not related to in vitro sperm quality but resulted from a higher ability to remove glycerol, a higher storage capacity in the female reproductive tract, and a longer fertility ability. Since no impacts were observed in sperm cellular characteristics, further experiments are necessary to investigate the influences of glycerol removal treatments at the molecular level.