The length of the cycle of seminiferous epithelium in goats (Capra hircus). 
This is the first report in literature showing the length of the seminiferous epithelium cycle in goats.  In the present study, the duration of spermatogenesis was estimated using intratesticular injections of tritiated thymidine.  Animals were castrated at 4 h, 7 days, and 11 days after injections.  The duration of each spermatogenic cycle in goats is 10.6 +/- 0.5 days (SEM).  Considering that the total duration of spermatogenesis takes about 4.5 cycles of seminiferous epithelium, spermatogenesis was estimated to last 47.7 days.  The approximate primary spermatocytes life span is 14.1 days, while spermiogenesis in goats lasts 14.9 days.  Staging in goats was based on the tubular morphology, where 8 stages of the cycle are yielded for all species.  The relative stage frequencies in goats, based on 400 seminiferous tubule cross sections for each animal were as follows: stage 1: 15.8 +/- 1.0%; stage 2: 12.8 +/- 0.5%; stage 3: 20.5 +/- 0.9%; stage 4: 10.7 +/- 0.7%; stage 5: 11.6 +/- 0.6%; stage 6: 9.3 +/- 1.1%; stage 7: 7.6 +/- 0.4%; stage 8: 11.7 +/- 0.6%.  The pre-meiotic, meiotic and post-meiotic phases' relative frequencies were 49.1%, 10.7% and 40.2%, respectively.  The duration of spermatogenesis in goats is very similar to that found in rams.