Use of Doppler Ultrasound to Evaluate Testicular Blood Flow Dynamics in Bulls

Evaluation of the testicular hemodynamics can significantly contribute to understand the thermoregulatory mechanisms and oxygen supply of the testis in domestic animals. The objective of this study was to evaluate the circulatory dynamics of the testicular arteries in bulls during four consecutive seasons. We evaluated
bulls (Hereford n = 24 and Angus n = 29) by means velocimetry parameters (Vel), pulsatility index (PI) and resistance index (RI) using Doppler ultrasonography. All procedures were approved by the Ethical Committee for Care and Use of Experimental Animals (#18656/2014/58). In addition, climate temperature-humidity index (THI) data were collected from an automatic weather station from the National Institute of Meteorology. Data were analyzed using ANOVA (GLM) and Pearson’s correlation with significance level of 5%. No differences were observed between breed and breed*season; however, season was difference between evaluated animals. The THI was lower in the fall (46.8) compared to winter (66.9), spring (71.9) and summer (72.7). Blood flow velocity (cm/sec) showed difference between fall (7.44 ± 2.72) compared to winter, spring and summer (12.74 ± 4.30; 12.74 ± 3.87 and 11.33 ± 3.42, respectively; P < 0.05). In addition, PI showed difference in the fall (0.45 ± 0.15) compared to winter, spring and summer (0.33 ± 0.20; 0.35 ± 0.17 and 0.27 ± 0.17, respectively; P < 0.05). We observed no difference in RI indexes between evaluation periods. In the fall season, we observed a positive correlation (0.87) between PI and RI (P < 0.05) indices; however, a negative correlation was observed between Vel x PI (-0.60) and Vel x RI (-0.59). In the fall, when THI is lower, there is a decrease in Vel of the blood flow arteries and an increase of PI in the circulatory dynamics in the pampiniform plexus area. Therefore, there is no need for additional nutrients supply when the testicular blood flow is lower due to the less heat dissipation by the scrotum to maintain an ideal temperature for normal spermatogenesis. We concluded that there is difference in Vel and PI of the supratesticular arteries from animals evaluated in the fall season. Therefore, the Doppler ultrasound can be used to evaluate scrotal blood flow changes of the pampiniform plexus during season and it suggests that differences in Vel and PI dynamics are an important players in the physiological requirements for its normal reproductive performance under different environmental conditions.