Seminal vesicle activity during cyclic or stabilized testicular activity in rams

Abstract

Four groups of adult rams (six rams per group) were exposed to different light regimes over 2 years to study the influence of photoperiod on seminal vesicle activity during testicular regression and redevelopment. Group 1 was exposed to continuous short days (8L: 16D). Groups 2, 3 and 4 were exposed to 4 months of short days alternated with 1, 2 or 4 months, respectively, of long days. Seminal fructose and citric acid levels were determined every 2 weeks and compared with serum testosterone levels. In all animals, changes in seminal fructose level paralleled changes in testosterone level ( r = 0.61). Corresponding changes in citric acid levels were less noticeable ( r = 0.34). A change from long days to short days induced an increase in fructose level from 2.6 to 5.7 mg ml −1, corresponding to an increase in testosterone level ( P < 0.05). The reverse occurred after a change from short days to long days. With exposure to continuous short days, fructose remained at elevated levels during the last 11 months of the study, corresponding to sustained elevated testosterone levels ( P < 0.05). These data are consistent with the view that fructose levels in semen reflect prevailing androgenic activity and demonstrate that fructose in ram semen can be maintained at elevated levels by exposing rams to continuous short days.