Relationship of 5α-reductase and androgens with sperm quality during breeding and non-breeding seasons in Arabi rams

Seasonal changes in the sperm quality of rams may be influenced by the activity of 5α-reductase (5αR) and androgens, i.e., testosterone and dihydrotestosterone (DHT). The aim of this study was to investigate the variation in the levels of 5αR type 2 (5αR2) and androgens in serum and seminal plasma and their association with sperm quality parameters during the breeding season (BS) and non-breeding season (NBS) in Arabi rams. A total of ten adult pure Arabi rams with 3.5 ± 0.5 years old were used. Semen and blood samples were collected during the breeding and non-breeding seasons. Sperm quality parameters were evaluated by routine methods. 5αR2, testosterone and DHT concentrations in serum and seminal plasma were determined. Sperm characteristics including concentration, motility and viability as well as serum parameters including 5αR2, testosterone and DHT were significantly higher in BS than NBS (P < 0.05). Furthermore, content of DHT and the conversion rate of testosterone to DHT in seminal plasma were higher in BS compared to NBS (P < 0.05). In BS, there was a positive correlation between 5αR2 and DHT levels in both of the serum (P < 0.01, r = 0.96) and seminal plasma (P < 0.01, r = 0.91). During BS, serum 5αR2 and DHT levels had a positive correlation with motility rate (P < 0.05, r = 0.72 and 0.77, respectively) and concentration (P < 0.01, r = 0.93 and 0.95, respectively) of spermatozoa. Sperm quality parameters of rams improve during natural BS, which can likely be due to an increase in 5α-reductase enzyme activity and therefore a higher serum DHT/testosterone ratio in BS than in NBS.