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Context Testicular blood flow (TBF) is crucial for testicular function. The pattern of TBF in Shiba goats indicates seasonal variations. Aims This study aimed to investigate the effect of diurnal variations on TBF, testis volume (TV), testicular echogenicity, and reproductive hormones in goats over a 24-h period. Methods In three trials that went for three consecutive days each, 12 bucks were scanned using Triplex ultrasonography to assess the TV, pixel intensity of testicular echotexture (PIX), and Doppler indices of TBF (resistive index: RI and pulsatility index: PI) in four-time points a day (at 6.00, 12.00, 18.00, and 00.00 h). Concomitantly, the changes in circulating FSH, LH, inhibin, testosterone (T), estradiol (E2), cortisol, and melatonin were assessed. Key results Results revealed diurnal alterations in the calculated RI of TBF and the PIX of testicular parenchyma (P < 0.05). Lower RI values of the TBF were observed at 6.00 h compared to other time points. There were significant diurnal alterations in the levels of FSH (P < 0.05), LH (P < 0.05), T (P < 0.0001), E2 (P < 0.0001), cortisol (P < 0.0001), and melatonin (P < 0.0001). FSH attained a higher concentration at 18.00 h compared to 12.00 h. Concentrations of LH were significantly higher at 06.00 h compared to those at 18.00 h. Concentrations of T were significantly higher at 6.00 compared to other time points. E2 showed higher concentrations at 6.00 h and 00.00 h compared to 12.00 h and 18.00 h. On the contrary, concentrations of cortisol were significantly higher at 12.00 h and 18.00 h compared to 06.00 h and 00.00 h. The highest concentrations of melatonin were observed at 00.00 h compared to other time points, while the lowest concentrations were at 12.00 h. Conclusions Diurnal rhythm induces significant changes in TBF, testicular PIX, and circulating FSH, LH, T, E2, cortisol, and melatonin over the 24-h day. Implications The outcomes of the study are reflected in the advisability of monitoring the TBF at a fixed time a day to avoid the circadian rhythm effect.

In all organs, control of blood flow is important but might be particularly critical for testicular functions. This is because of the very low oxygen concentration and high metabolic rate of the seminiferous tubules, the physiological temperature of the testis, and its location outside the abdominal cavity. Many factors affect the characteristics of TBF in farm and companion animals, such as environment (thermal and seasonal effects) and physiological (species, breeds, age, body weight, and sexual maturity). Thermal environment stress has detrimental effects on spermatogenesis and consequently has more serious impacts on both human and animal fertility. Numerous studies have been performed to assess TBF in different animal species including bulls, rams, bucks, alpacas, stallions, and dogs with varied results. Hence, assessment of TBF by Doppler ultrasonography is of great importance to estimate the effect of high environment temperature on testicular functions. Also, differences observed in the TBF may result from different technical aspects such as the identification of the segment of the testicular artery to be examined. In the current review, we focused on the imperative roles of TBF in various animal species. Besides, we discussed in detail various factors that could affect TBF. These factors can significantly modify the TBF and thus should be considered when establishing reference values in farm animals for better clinical diagnosis. The information provided in this review is valuable for researchers and veterinarians to help them a better understanding of testicular hemodynamics for the proper evaluation of breeding soundness examination in males.

Under field conditions, sedation may be required for a full assessment of the reproductive potential of farm animals. The present study aimed to investigate the effect of xylazine sedation on testicular hemodynamics (TBF), echotexture, testicular volume (TV), and circulating hormones in goats. Sixteen male Shiba goats were sedated using the recommended dose of xylazine (0.05 mg/Kg BW). Testicular hemodynamics were evaluated using color pulsed Doppler ultrasonography before and after sedation. Echotexture of the testicular parenchyma and TV were assessed using computerized image analysis. Concentrations of testosterone, estradiol (E2), inhibin, cortisol, follicle-stimulating hormone (FSH), and ‎ luteinizing hormone (LH) were measured using radioimmunoassay. There were no effects of xylazine sedation in TBF, TV, testicular parenchyma parameters, testosterone, inhibin, FSH, and LH (P ˃ 0.05). However, after sedation, there was significantly (P ˂ 0.05) lower cortisol and E2 concentration (42.88 ± 6.79 ng/ml and 2.47 ± 0.58 pg/ml, respectively) than before sedation (94.89 ± 13.74 ng/ml and 8.65 ± 1.79 pg/ml, respectively). The required time to perform full scanning of the testis was significantly lower (8.50 ± 1.50 min) after xylazine sedation compared to the non-sedated goats (25.75 ± 4.57 min). In conclusion, xylazine sedation may be practically recommended for the evaluation of TBF in goats because it did not significantly alter velocities parameters and Doppler indices of blood flow within the testicular arteries. Most plasma hormones did not significantly change; however, E2 and cortisol were significantly reduced after xylazine administration.

Under eld conditions, sedation may be required for a full assessment of the reproductive potential of farm animals. The present study aimed to investigate the effect of xylazine sedation on testicular hemodynamics (TBF), echotexture, testicular volume (TV), and circulating hormones in goats. Sixteen male Shiba goats were sedated using the recommended dose of xylazine (0.05 mg/Kg BW). Testicular hemodynamics were evaluated using color pulsed Doppler ultrasonography before and after sedation. Echotexture of the testicular parenchyma and TV were assessed using computerized image analysis.Concentrations of testosterone, estradiol (E2), inhibin, cortisol, follicle-stimulating hormone (FSH), and luteinizing hormone (LH) were measured using radioimmunoassay. There were no effects of xylazine sedation in TBF, TV, testicular parenchyma parameters, testosterone, inhibin, FSH, and LH (P 0.05). However, after sedation, there was signi cantly (P 0.05) lower cortisol and E2 concentration (42.88 ± 6.79 ng/ml and 2.47 ± 0.58 pg/ml, respectively) than before sedation (94.89 ± 13.74 ng/ml and 8.65 ± 1.79 pg/ml, respectively). The required time to perform full scanning of the testis was signi cantly lower (8.50 ± 1.50 min) after xylazine sedation compared to the non-sedated goats (25.75 ± 4.57 min). In conclusion, xylazine sedation may be practically recommended for the evaluation of TBF in goats because it did not signi cantly alter velocities parameters and Doppler indices of blood ow within the testicular arteries. Most plasma hormones did not signi cantly change; however, E2 and cortisol were signi cantly reduced after xylazine administration.

The beneficial effects of melatonin were investigated to mitigate various detrimental effects and toxicity on reproductive performance. The present study aimed, for the first time, to explore the effect of intravenous melatonin injection on testicular artery hemodynamics (TH) and metabolomic changes, reproductive hormones in heat-stressed bucks. Ten bucks were randomly split into two groups (five each): (1) the melatonin group, treated with a single intravenous dose of melatonin solution containing 10 mg melatonin each, and (2) the control group, which was treated with 10 mL of the vehicle without melatonin. Changes in the TH at the level of the supra testicular artery (STA) were assessed by triplex ultrasonography just before (0 h) and at 0.5, 2, 7, 24, and 168 h after melatonin or vehicle administration. Doppler velocity parameters of peak systolic velocity (PSV; cm/s), end-diastolic velocity (EDV; cm/s), and time average maximum velocity (TAMAX; cm/s) were measured. Doppler indices (resistive index; RI and pulsatility index; PI), systole/diastole (S/D) ratio and total arterial blood flow volume (TABFV; ml/minute) were measured. Peripheral concentrations of FSH, LH, inhibin, melatonin, testosterone (T), estradiol (E2), and cortisol were measured just before injection (0 h) and at 0.5, 2, 7, and 24 h and daily up to day 7 post administration in both groups. Results revealed reductions in the RI values and increases in the TABFV in the melatonin group compared to the control one, especially 2 h after administration. Significant increases in concentrations of FSH, T, E2, and melatonin and decreases in cortisol and inhibin in the melatonin group compared to the control one. Plasma metabolomic analysis at 2 h indicated the up-regulation of L-glutamine, L-arginine, sorbitol, D-glucose, ascorbic acid, and ornithine and the down-regulation of D-xylose, D-arabitol, ribitol, and oleic acid in the melatonin versus the control group. In conclusion, acute administration of melatonin (10 mg IV) enhanced testicular artery blood flow and plasma reproductive hormones in the Shiba goat under heat-stress circumstances.