Active immunization against GnRH in ovine (Ovis aries): testicular morphometry, histopathology and endocrine responses in prepubertal ram lambs

Abstract

The main objective of the present research was to assess the effects of an active immunization against GnRH on male reproductive function as an alternative to surgical sterilization evaluating testicular morphometry, histopathological alterations and plasma gonadotropin levels in prepubertal ram lambs. Dorper ram lambs (age= 2 months; control group, n= 5; treatment group, n=15) were immunised by using an anti-GnRH vaccine (two administrations spaced 15d) developed by linking a GnRH homologous molecule to tetanus toxoid (clostridial toxoid) with aluminum hydroxide as coadjuvant. To determine the effectiveness of the vaccination protocol, testicular morphometry was evaluated (length, width, mean volume and total volume) together with histopathological alterations in testicular tissue samples (seminiferous tubule diameters, spermatogonia per testis and sperm presence) and endocrine responses (ELISA) from blood samples (FSH, LH, testosterone and cortisol plasma levels). Morphometric parameters (testicular length, width and volume) were significantly reduced in vaccinated animals with respect to the control group (p0.05). In conclusion, prepubertal active immunization against GnRH led to marked differences on testes morphometry and activity in ovine species, however, it did not affect endocrine levels nor spermatogenesis in all individuals studied showing a partial vaccination effect in some of them. Thus, taking into account the heterogeneous dysfunctional responses obtained, different vaccination assays and strategies should be tested before active immunization against GnRH is considered as a viable alternative to conventional surgical sterilization.

Keywords

• active immunization
• GnRH; testicular histopathology
• endocrine response
• ovine
• GnRH
• Testicular histopathology