Hemodynamic evaluation of the supratesticular artery in bulls

•Evaluation of testicular hemodynamics with US Doppler during the year's seasons.•Higher values of THI were correlated with higher blood flow.•THI affects testicular hemodynamics values due to a physiological reflex. The evaluation of testicular hemodynamics can contribute significantly to understanding the thermoregulatory mechanisms and the supply of oxygen in the testis in domestic animals. The aim of this study was to evaluate the testicular hemodynamics used in Color Doppler ultrasonography in bulls of the Aberdeen Angus and Polled Hereford breeds at four different moments (C1, C2, C3 and C4) during the seasonal variations in bovine breeding animals. Twenty-eight bulls (Polled Hereford n = 12 and Aberdeen Angus n = 16) were evaluated by means of velocimetry (MV), pulsatility index (PI) and resistance index (RI) using Color Doppler ultrasonography. The climate temperature and humidity index (THI) data were collected from an automatic meteorological station of the National Institute of Meteorology. Data were analyzed using ANOVA and Tukey's test and Pearson's correlation with significance level of 5% were used. Preliminary analyses showed no differences within breeds, or interaction breed and collection. However, significate difference was observed when the time of collection (C1, C2, C3 and C4) was evaluated. The MV of blood flow (cm/s) was different in C3 (7.53 ± 2.66) compared to C4, C1 and C2 (13.63 ± 4.24, 13.57 ± 4.32 and 10.97 ± 3.37, respectively; P < 0.05). There was a positive correlation (0.831) between the PI and RI indices (P < 0.05), and a negative correlation between MV x PI (-0.361) and MV x RI (-0.208). The higher values of THI presented higher blood flow in the supratesticular artery. Low THI affect the values of testicular hemodynamics due to the physiological reflex of the scrotal thermoregulation, causing a peripheral vasoconstriction in response to low temperatures, resulting in a lower average velocity of blood flow of the supratesticular artery. Doppler ultrasound can be used to assess changes in the scrotal blood flow of the pampiniform plexus during the collections and suggests that differences in VM, PI and RI dynamics are important actors in the physiological requirements for their normal reproductive performance under different environmental conditions.