Abstract
BackgroundSemen evaluation is used to estimate the testicular function. In bulls, the spermatozoa present in the ejaculate are the result of a process that begun more than 2 mo earlier, bequeathing a delayed depiction of the actual function of the testis. Since testis vascularization might be critical for the gonad function, selected pulse wave Doppler ultrasound parameters were assessed in this study, for instance the peak systolic velocity, the end diastolic velocity and the resistive index of the testicular artery along the spermatic cord, the marginal portion of the testicular artery and the intratesticular branches of the testicular artery both in healthy adult and young bulls. Correlations between these parameters and characteristics of semen that was collected numerous times, before and after the Doppler ultrasound examination.ResultsThe peak systolic velocity and the end diastolic velocity measured in the testicular artery along the spermatic cord (supratesticular artery – SA) were variable among the bulls and within individual bulls, likely due to the convoluted course of the vessel. The resistive index was found highly repeatable in the same bull. A reduction in the resistive index was found between the supratesticular artery and the marginal portion of the testicular artery (P < 0.01), and between the marginal portion of the testicular artery and the intratesticular branches of the testicular artery (P < 0.05). No differences were recorded for the pulse wave Doppler ultrasound parameters in young bulls compared with adults. A significant correlation was found between the resistive index of the marginal portion of the testicular artery and total sperm in the ejaculate (r = 0.516, P < 0.05), the immature sperm (r = 0.462, P < 0.05), the teratoid sperm (r = 0.375, P < 0.05), and the “Dag defect” sperm (r = 0.389, P < 0.05). Similarly, the resistive index of the intratesticular branches of the testicular artery were found correlated with the total sperm number in the ejaculate (r = 0.568, P < 0.05), the immature sperm (r = 0.523, P < 0.05), the teratoid sperm (r = 0.418, P < 0.05), and the “Dag defect” sperm (r = 0.341, P < 0.05).ConclusionsThe data presented in this study suggest that the resistive index, measured at the marginal portion of the testicular artery, could be an easy-to-perform parameter to evaluate the spermatogenesis quality in young bulls and normal adults.
Highlights
Semen evaluation is used to estimate the testicular function
All pulse wave Doppler ultrasound (PWDU) values (PSV, end diastolic velocity (EDV), resistive index (RI)), were significantly higher (P < 0.01) in spermatic cord testicular artery (SA) than in marginal portion of the testicular artery (MA), which was in turn significantly higher (P < 0.05) than the intratesticular branches of the testicular artery (IA) for peak systolic velocity (PSV), and RI
The generalized linear model (GLM) for repeated measures showed that the values of PSV and EDV recorded in the SA artery were significantly variable (P < 0.01) in the same bull, but the MA and the IA were similar (P < 0.05)
Summary
Semen evaluation is used to estimate the testicular function. In bulls, the spermatozoa present in the ejaculate are the result of a process that begun more than 2 mo earlier, bequeathing a delayed depiction of the actual function of the testis. Since testis vascularization might be critical for the gonad function, selected pulse wave Doppler ultrasound parameters were assessed in this study, for instance the peak systolic velocity, the end diastolic velocity and the resistive index of the testicular artery along the spermatic cord, the marginal portion of the testicular artery and the intratesticular branches of the testicular artery both in healthy adult and young bulls Correlations between these parameters and characteristics of semen that was collected numerous times, before and after the Doppler ultrasound examination. Since the duration of spermatogenesis in the bulls takes approximately 62 d, and the epididymal transit takes 11 d [2], the mature spermatozoa that are present in the ejaculate had entered spermatogenesis approximately 70 d earlier For this reason, the results of semen evaluation performed at any given time, reflect an actual testicular function with a significant delay [3]. Kay et al [11] reported that a totally absent spermatogenesis, or existing only in a small proportion of seminiferous tubules, was obtained by the experimentally-induced restriction of the testicular artery in bulls, demonstrating the central role of the perfusion in the testicular function
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