Semen quality, testosterone values, and testicular and accessory gland parameters in rams receiving sustained stimulation with low doses of buserelin

Abstract

Context The use of buserelin, a gonadotropin-releasing hormone (GnRH) agonist, can improve semen quality. Nevertheless, the appropriate dosage, and frequency and time of application, remain to be established owing to the subsequent negative feedback on endogenous production of testosterone described so far. Aims This study aimed to propose a new buserelin application protocol for sperm improvement in Santa Inês rams. Methods Fifteen Santa Inês rams were divided into two experimental groups: the first group (n = 8) received 2.5 μg buserelin acetate; and the second group (n = 7) received saline solution. Treatments were applied for 21 days at intervals of 6 h, totalling four hormonal or saline applications per day. In all animals, macroscopic and microscopic seminal characteristics and freezability, plasma testosterone, pixels of testicular parenchyma, and biometric analysis of testicular and accessory sex glands by ultrasound were evaluated throughout the period of hormonal application and for a further 7 days. Key results Rams receiving buserelin showed a peak of testosterone after the first week (Day 7) of application, with a drop in values at Day 14, followed by negative feedback at Day 21 and return to basal concentrations at Day 28. They also showed improvement of kinetics parameters such as straight line velocity (μm/s: +buserelin 51.5 ± 1.5 > control 46.6 ± 1.6) and linearity coefficient (%: +buserelin 53.5 ± 1.8 > control 47.5 ± 1.9). Ultrasound parameters, pixels of testicular parenchyma, and freezability were not affected by treatment. Conclusions The administration of buserelin was able to improve some sperm kinetics parameters of Santa Inês rams. Implications Low doses of this GnRH analogue can be used; however, further adjustments to the hormonal protocol are needed to obtain an effective improvement in sperm quality.