Impact of old age and season on Chios ram semen quality

The present study aimed to provide new and objective information regarding the effect of season and age on the characteristics of Chios ram semen. The semen collection was performed biweekly throughout a year, including both breeding and non-breeding periods. Seven active Chios rams were divided in two age groups: three rams of 2-6 years old (mature) and four rams of 9-13 years old (old). After collection, semen volume and sperm concentration were measured. One hundred sixty-eight (168) semen samples were collected, extended and evaluated. All samples were tested for motility and kinetics (Computer Assisted Sperm Analyzer), viability-membrane integrity (Eosin-Nigrosin), morphology (SpermBlue (R)), chromatin integrity (Acridine Orange Test) and sperm membrane biochemical functionality (Hypo-osmotic swelling test, HOST). Motility did not differ significantly between periods (p > 0.05) or between age groups (p > 0.05). The percentage of hyperactivated spermatozoa and head abnormalities was higher in the non-breeding compared to the breeding period (p = 0.011 and p = 0.001, respectively). Tail abnormalities were higher in the breeding (p = 0.022) and HOST + spermatozoa were lower in the non-breeding period (p < 0.001). Significantly higher values of semen volume (p = 0.001) and concentration (p < 0.001) were noticed in old compared to mature rams. In conclusion, old rams, up to the age of 13 years, preserve high semen quality, while season affects ram sperm membrane biochemical functionality and head morphology.