Reproductive parameters of lambs immunocastrated with anti-GnRH vaccine

Abstract

The objective of this study was to evaluate the testicular biometric, seminal, and plasma testosterone levels in lambs subjected to an anti-GnRH vaccine as a method of castration. Thirty entire, crossbred Santa Inês male lambs were randomly distributed into three treatment (T): T1 was the control group, with the administration of 1 mL of saline solution subcutaneously (SC); 1.0 and 0.5 mL of an anti-GnRH vaccine were administered SC in T2 and T3, respectively. Testicular biometric variables, physical and morphological variables of semen, and plasma testosterone concentrations were evaluated. At D60, there was a reduction in testicular length, width, thickness, and scrotal circumference of the immunocastrated animals regardless of the vaccine dose used (P < 0.05). A reduction in semen physical variables at both dosages (P < 0.05) was observed, with azoospermia, in 80% and 70% of animals in the T2 and T3 groups, respectively. At D60, the immunocastrated animals also showed an increase in spermatozoa defects (P < 0.05), whereas plasma testosterone concentration decreased (P < 0.05). Immunocastration of lambs using the Bopriva vaccine at doses of 1.0 and 0.5 mL is efficient in inducing azoospermia in up to 80% of animals, although two doses in a 30-day interval are necessary for it to be an effective and safe method. Efficacy was demonstrated through a reduction in serum testosterone levels, testicular biometry, and seminal fluid analysis. Considering the efficacy of both doses in this study, we recommend using the lower dose (0.5 mL), which will allow for a 50% reduction in vaccine costs.

How Well Does Australian Animal Welfare Policy Reflect Scientific Evidence: A Case Study Approach Based on Lamb Marking

“…This method blocks the normal functioning of the hypothalamic–pituitary–gonadal axis by administering two doses of vaccine against gonadotrophin-releasing hormone (GnRH). Immunisation against GnRH results in the suppression of testosterone production and spermatogenesis [ 12 , 14 ]. While this technique has been widely adopted in pigs, there is currently no licenced product in sheep [ 13 , 14 , 15 ].…”

“…Immunisation against GnRH results in the suppression of testosterone production and spermatogenesis [ 12 , 14 ]. While this technique has been widely adopted in pigs, there is currently no licenced product in sheep [ 13 , 14 , 15 ].…”

Effect of GnRH immunocastration on immune function in male rats

“…Gonadotropin-releasing hormone (GnRH) is a pivotal hormone of HPGA, and it regulates reproduction through the HPGA. In the past decades, GnRH has been used as an immunocastration antigen in pigs (7)(8)(9)(10)(11), calf (12)(13)(14), goats (15)(16)(17), chickens (18), horses (19)(20)(21), and some wild animals (22,23) to reduce their aggression, increasing yield, and improve the meat quality (24) or to control the reproduction of wild animals (22,23). Many studies have confirmed that GnRH has impacts on the development and functions of immune system (3,25).…”