Testicular fluid content evaluated by ultrasound image computer-assisted analysis increases with small-dose multiple GnRH injections in rams

The aim of the work was to determine whether multiple small doses of GnRH induce an increase in testicular blood flow and scrotal temperature in rams. The experiment was performed during the late breeding season (May-June) with 14 one-year-old rams. Seven rams received hourly doses of 7 ng of a GnRH analogue (busereline acetate) iv starting at 8:00 on the morning, and the other seven rams remained as controls. One week later, treatments were overcrossed. One hour before the first GnRH dose (7:00), and 0, 1, 2, 4, 7 and 10 h later, ultrasonographic examinations of the testes were performed with a B-mode ultrasound scanner with a 7.5 MHz linear array transducer. Each testicle was examined separately by placing the transducer vertically. Images were analysed with specific software using the spot metering technique in four spots with a diameter of 1 cm on the same place of the image. At the same times, rectal, anal and scrotal surface temperatures were measured with a laser thermometer. Pixel intensity was lower with time (blacker, p < 0.0001), as a consequence of GnRH treatment (p < 0.0001). Differences between pixel intensities were significant starting 1 h after the first GnRH dose (p < 0.0001). Perineal temperature (33.9 ± 0.2°C) was not affected by treatment or time (p > 0.1). Rectal temperature was similar in both groups (p < 0.05) until 4 h after the beginning of the treatment (13:00 h). The differences between treatments increased since 4 h after the first dose of GnRH. Scrotal surface temperatures were not affected by treatment (p > 0.1). We concluded that multiple small GnRH doses trigger a rapid increase in testicular fluid content not accompanied by changes on scrotal surface temperature.