Endocrine Profiles, Testicular Gonadotropin Receptors and Sperm Production in Hemi-Castrated Ram Lambs

Abstract

The effects of hemi-castration upon compensatory hypertrophy, serum gonadotropin and testosterone concentrations, testicular gonadotropin receptors and daily sperm production (DSP) were studied in 10 crossbred ram lambs. At 4 mo of age lambs were either hemi-castrated (HC; n=5) or left intact (INT; n=5). Blood samples were collected every 2 h for the first 24 h post-surgery, every 6 h for the next 24 h and then three times weekly for the following 14 wk. Serial blood samples (15-min intervals for 8 h) were collected during the 4th, 8th and 12th week following hemi-castration. Individual mean testicular and epididymal weights increased (P<.05) 48 and 33% in HC compared with INT rams, respectively. Serum follicle stimulating hormone (FSH) increased (P<.05) within 8 h after HC, reached peak concentrations within 1 wk and remained elevated for 4 wk before returning to concentrations of INT rams. Neither mean serum luteinizing hormone (LH) nor pulse patterns of LH or FSH were different (P>.05) between these two groups at any period examined. Serum testosterone (T) concentrations were lower (P<.05) during the first 48 h post-surgery in HC rams, but by 1 wk concentrations were similar (P>.05) to those in INT rams. Remaining testes from HC and INT rams were removed at 7 mo of age, 3 mo after initial gonadal manipulation. On a per-testis basis there were more (P<.05) LH and FSH receptors in HC than INT rams, respectively; however, concentrations of receptors were not different (P>.05). Similarly, DSP/ testis was greater (P<.05) for HC than INT animals, while DSP/g parenchyma was similar (P>.05). These results indicate: 1) increased serum FSH was related to compensatory hypertrophy, 2) complete compensation of androgen secretion in HC rams was not related to a complete compensation in testicular size, alterations in secretion of serum LH or in changes of testicular gonadotropin receptor concentrations and 3) the increase in DSP in the remaining testis following hemi-castration was not associated with an increase in spermatogenic efficiency of the testicular tissue.