Effective tools for male contraception are important in the control of reproduction in animal populations. The aim of the present study was to evaluate the effects of active immunization against gonadotropin-releasing hormone (GnRH) on male reproductive function assessing testicular morphological changes and serum-gonadotropin levels in pre-pubertal rabbits, guinea pigs and ram lambs. An anti-GnRH vaccine was developed by linking a GnRH-homologous molecule to a tetanus clostridial toxoid (Al(OH)3 coadjuvant). After vaccination protocols testicular morphometry, histopathological alterations and endocrine responses (FSH, LH, testosterone and cortisol serum levels) were evaluated. Testicular volume was significantly reduced in vaccinated animals with respect to the control group in rabbits, guinea pigs and ram lambs (P<0.05 to P<0.001). The anti-GnRH vaccine generated a reduction in testicular volume of 15-, 27- and 11-fold, respectively. Tubule diameters decreased in the vaccinated group with respect to the control ~2.0-, 1.2- and 3.5-fold, respectively (P<0.001). Tubule, intertubular and lumen volumes significantly decreased in vaccinated rabbits (P<0.05), guinea pigs and ram lambs (P<0.01). Vaccinated animals of the three species showed significant reductions in spermatogonial numbers (10- to 40-fold; P<0.01). Sperm was absent in all seminiferous tubules of all rabbits, and most individuals of guinea pigs (80%) and ram lambs (60%). No significant differences were observed between vaccinated and control groups regarding FSH and LH during the experiments in the three experimental species/models used. Testosterone, however, was only significantly lower (~22-fold, P<0.01) in vaccinated rabbits. In conclusion, the present study demonstrated that pre-pubertal active immunization against GnRH leads to endocrine disruption and marked differences on testicular morphometry, development and activity among lagomorphs, hystricomorphs and ovine species with species-specific sensitivity regarding the anti-GnRH immune response.

The protein-rich non-conventional detoxified karanja cake (dKC) can be used in place of conventional protein supplements like soybean meal (SBM), groundnut meal, etc. in livestock feed. The present study was conducted to assess the effect of two levels of dKC by replacing SBM on testicular architecture, semen quality and expressions of mRNAs encoding luteinizing hormone receptor (LHR) and insulin-like growth factor (IGF-I) in testes of ram lambs. Eighteen ram lambs were randomly divided into three groups (n = 6) and fed different levels (%) of karanja cake (0% replacement – control; 50% replacement – dKC-50 and 75% replacement – dKC-75) for 140 days. After 120 days of feeding, the semen from the animals was collected and analysed. The testes samples were collected on day 140 of feeding for transcripts expression studies. The dKC-50 group had no change in BW, whereas dKC-75 group showed decreased (P < 0.05) BW as compared with control. The number of animals ejaculated semen in dKC-75 group was lower (P < 0.05) than the control group. A reduction (P < 0.05) in LHR expression in dKC-75 was observed, whereas a reduction in IGF-I expression (P < 0.05) was observed in dKC-50 and dKC-75 as compared with control group. The study reveals that in ram lambs, long-term feeding of dKC at 50% replacement of SBM may not affect BW. However, long-term feeding of dKC as a replacement of SBM may affect testicular function.