Examination of jackass (Equus asinus) accessory sex glands by B‐mode ultrasound and of testicular artery blood flow by colour pulsed‐wave Doppler ultrasound: Correlations with semen production

Abstract

The accessory sex glands play a major role in the production of seminal plasma, and testicular artery blood flow seems to strongly influence testicular function. However, very little ultrasound imaging of these organs has been undertaken in donkeys. The present work reports the results of such examinations in five jackasses along the year. The accessory glands were inspected by B‐mode ultrasound while the testicular artery blood flow was assessed by colour pulsed‐wave Doppler ultrasound. The testicular artery was examined at pampiniform plexus (PPT), supratesticular area (ST) and capsular artery (CA). Values were recorded for the total arterial blood flow (TABF), peak systolic velocity (PSV), end‐diastolic velocity (EDV), resistive index (RI), pulsatility index (PI) and time average maximum velocity (TAMV). Semen was obtained and assessed for sperm concentration, viability, abnormalities and motility using a CASA system. The bulbourethral glands, prostate and ductus deferens ampullae were relatively larger than in the stallion. Bulbourethral glands and ampullae sizes were inversely correlated with sperm motility. An reduction in blood flow between the level the PPP and the CA was observed, helping to reduce testis temperature and oxygen pressure. Blood flow at the CA showed the strongest correlation with semen production. PI and RI were positively correlated with the CASA motility variable STR (p = .02, p = .06) and sperm viability (p = .01), while sperm concentration (p = .05) correlated inversely with PSV, EDV, TAMV and TABF. EDV also correlated negatively with the CASA variables VSL, LIN, STR and VAP (p ≤ .05). PI and RI were also negatively correlated with testis length (p = .0093, p = −.0438).

Multivariate models for estimating jackass semen production and quality

“…Ultrasonography is an easily applicable non‐invasive method for assessing the gonad and accessory sex gland and detecting different pathologies, and provides information related to the clinical fertility evaluation of animals (Kandiel & Shafey, 2017). Although ultrasound examination of gonads and accessory gonads in donkeys has been reported (Contri et al., 2008; Gacem et al., 2020; Pricking et al., 2017), studies on the effects of seasons on the glands are limited. Abou‐Elhamd et al.…”

“…Gacem et al. (2020) reported bulbourethral glands and ampulla sizes were inversely correlated with sperm motility of jackass. In contrast, Contri et al.…”

“…Additionally, compared with LSM, male donkeys in HSM1 had wider long axis of the spermatic cord also and larger vascular diameter in this study (Figure 3d,e). The vasal and cremasteric arteries coil in the proximal pampiniform plexus of the spermatic cord before entering the testes, helping to reduce testis temperature (Lloyd‐Jones et al., 2015) and to reduce the tissue oxygen pressure (Gacem et al., 2020). This implies that the wider long axis of the spermatic cord and blood vessels dilate increased heat dissipation and influence sperm quality.…”

“…In donkeys, the gonads and accessory sex glands can be easily examined by B‐mode (greyscale) ultrasound imaging (Gacem et al., 2018). However, only a few studies have reported an association between reproductive organs and semen production and quality based on ultrasonographic information (Gacem et al., 2020).…”

Optimization of CASA-Mot Analysis of Donkey Sperm: Optimum Frame Rate and Values of Kinematic Variables for Different Counting Chamber and Fields

“…However, comparative studies in both species have identified differences in reproductive strategy as well as in the sperm form and function [15,16]. Effectively, the donkey testis is bigger and has been proved to have more efficient spermatogenesis than a stallion [17][18][19][20]. In effect, donkey sperm heads are smaller with a larger mid-piece than the stallion resulting in differences in motility patterns [21].…”