The quality of chilled stallion semen in relation to its Freezability potential.

The current study aimed to compare the quality of chilled stallion semen depending on its frozen-thawed quality. Semen was collected once weekly for 3 successive weeks from 10 fertile Arabian stallions belonging to Al-Zahraa stud, Cairo, Egypt, using a stallion artificial vagina. Semen was extended in INRA -96 and centrifuged at 400g for 10 minutes. The sperm pellets were re-suspended to a final sperm concentration of 100 x 106 motile sperm/ml with INRA-96 either with or without 5% glycerol and 15% egg yolk. After cooling to 5oC, the chilled semen portion was kept at 5oC for 72 hours. The cryopreserved semen was packed in 0.5-ml straws, equilibrated at 5oC for 30 min, and placed 5cm above the liquid nitrogen level. The chilled and frozen-thawed semen samples were evaluated for progressive motility, plasma membrane integrity (Hypoosmotic swelling test), acrosome integrity (Giemsa staining), mitochondrial activity (MTT assay), and DNA integrity (Comet assay). Stallions were classified as good and poor freezers according to the results of frozen-thawed semen. The results of chilled semen were compared between the good and poor freezer stallions. The results revealed that the chilled semen of good freezer stallions has higher values of all semen parameters than that of poor freezer stallions (P < 0.01). In conclusion; the present study revealed that semen from good freezer stallions has higher post-storage semen quality either after chilling or cryopreservation compared to that of poor freezer stallions