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Schaffer, N.E.; Meehan, T.P.; Bryant, W.M.; Agnew, D.; Atkinson, M.W.; Wolfe, B., 2001. Ultrasonographic monitoring of electroejaculation in three species of rhinoceros (Ceratotherium simum, Diceros bicornis, Rhinoceros unicornis). Proceedings of the American Association of Zoo Veterinarians 2001: 343
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Location: World
Subject: Reproduction - Management methods
Species: All Rhino Species


Original text on this topic:
Methods for rectal ultrasonography. Rectal ultrasonography was performed with a handheld 5.0-MHz linear probe attached to an Aloka 500 scanner and recorded. The accessory glands in each animal were examined for size and echogenicity. The pelvis was examined from the bladder neck to the external pelvic brim. The structure of the pelvic urethra was identified postmortem by filling unfixed reproductive tracts with water. The effects of stimulation on the urethras of live animals were examined before and during procedures.
Two rhinos were anesthetized with 1 mg i.m. of carfentanil (Wildlife Pharmaceuticals, Inc.. Fort Collins, Colorado 80524, USA) for rectal electroejaculation. A 10-cm-diameter by 21-cm long rectal probe plated with two thin, 6 x 12-cm flat electrodes was placed just inside the anus. Electrical stimulations were performed in 2-sec pulses repeated 10 times each at 4, 5, 6, 7, and 8 V successively and, after a 1-2 min rest, at 6, 7, 8, and 9 V. The rectum and penis of rhinoceros I was massaged at the termination of electrical stimulation. Rhinoceros 2 was massaged throughout stimulation.
Rhinoceroses 3, 4, and 5 were trained to stand quietly with food enticement for rectal ultrasonography with or without restraint in a chute. Rhino 3 was also conditioned to penile massage and regularly produced semen samples. Rhino 4 had no prior penile massage conditioning, and rhino 5 was initially examined before a semen sample had been collected and again after the animal was producing semen samples approximately every other week. The back legs of rhinos 3, 4, and 5 were stroked until the penis was let down from the sheath, and the penis was then massaged directly.
Results
Ultrasonography of the postmortem water-filled reproductive tracts demonstrated a flattened bulbous expansion of the pelvic urethra between the bulbourethral glands and the prostate in both Ceratotherium simum (8x5x2 cm) and Rhinoceros unicornis (5x5x2 cm). Constriction of the bladder neck and prostatic urethra was the cranial border of the expansion, and constriction of the urethra at the bulbourethral glands was the caudal border. A dorsal-cranial bulge into the pelvic urethra just caudal to the cranial constriction was the colliculus seminalis.
Ultrasonography of postmortem morphology was similar to the images from the living animals except for the occurrence, in the live animals, of several small hypoechogenic lines in the colliculus seminalis. These lines were apparent in both resting and stimulated animals. Neither these ducts nor accessory glands grossly changed in their size or echogenicity during stimulatory methods.
Ultrasonography demonstrated that no fluid occurred in the pelvic urethra before electroejaculation began. Electrical stimulation caused rear leg extension and penile retraction. In one animal (rhino 1), the pelvic urethra filled in approximately 4 min after electrical stimulation was terminated. In animal 2, some filling occurred during the 1-min rest period between stimulation series, but maximal filling occurred at termination. In both animals, the urethra filled to a maximum depth of 2 cm, with lateral extensions of the fill area. This expansion was similar to the postmortem images. Massage during electroejaculation kept the penis out of its sheath and appeared ultrasonographically to cause clonic contractions of pelvic musculature and peristalsis of the pelvic urethra. The caudal urethral constriction opened allowing semen to flow into the penile urethra while the cranial constriction remained closed. Initially, when the semen moved into the penile urethra a slight delay occurred before expulsion. Downward pressure through the rectum onto the pelvic urethra and movement of the hand from the prostate caudally appeared to mechanically move the remaining fluid into the penile urethra. Once the urethra emptied, the muscle contractions stopped quickly and seminal emission did not appear to continue even with further stimulation of the penis.
For penile massage collections, stroking of the back legs stimulated the penis to drop from the sheath. Ultrasonography prior to massage revealed fluid in the pelvic urethra in the two conditioned rhinos, but not in the pelvic urethras of the unconditioned animals. In the conditioned rhinos, the filled areas of the urethra resembled and responded similarly to those in the electroejaculated animals. In the two conditioned rhinos, muscle contractions continued until the urethra emptied. In the two unconditioned rhinos, only a few contractions occurred with initial contact with the penis. Fluid with sperm was collected from three of the animals. In rhino 4, fluid was not evident in the urethra, but a small volume was collected during massage. In rhino 5 the urethra was filled, but emptied quickly with contact with the penis. The urethra did not refill upon further massage. In rhino 3, the urethra remained filled and the flow of seminal fluid continued. Massage of this animal was terminated when the cloudy fluid being collected began to clear, as this change had previously indicated a drop in sperm count. When massage was terminated in this animal, semen slowly drained from the pelvic urethra. Whether this semen flowed into the penile urethra or bladder was not apparent on ultrasonography. Semen did not subsequently flow from the penis. Rectal massage was not pursued with any of the animals given penile massage.
Discussion
Ultrasonography was useful for monitoring the effects of stimulation procedures on pelvic urethral morphology and seminal flow in the rhinoceros. These rhinoceroses exhibited the stages of ejaculation common to most mammals: seminal emission and ejaculation. For most species, seminal emission is the issuance of fluids from the vas deferens and accessory glands into the urethra, and ejaculation is the propulsion of fluid from the pelvic urethra by contraction of perineal musculature.
Changes in structure and echogenicity of the vesicular and ampulla glands did not occur in these rhinoceroses. The accessory glands of these rhinos appeared to be normal. Ampullae have not been evident anatomically or histologically in the white, black, or greater one-horned Asian rhinoceros. The rhinoceros vesicular gland compares more closely to the multisacculated structure of that in the bull, and changes in it may not be obvious.
Significant changes in size of the glands might be evident if measurements are made.
On ultrasonography, seminal emission filled a flattened bulbous expansion of the pelvic urethra. This pouch was similar to the area in the waterfilled postmortem specimens. It was shorter and closer to the ischial arch in Rhinoceros unicornis as compared to the African species. This pouch expanded laterally as well as longitudinally and was bordered by cranial and caudal constrictions. The pressure chamber in the rhinoceros may provide volume and force to the propulsion of semen through the extensive length of the penis and through the complicated cervix of the female. This expanded area occurred in these rhinoceroses caudal to the colliculus seminalis. On postmortem examination, the colliculus encompassed the openings into the urethra of the ejaculatory ducts of the prostate, vesicular gland, and vas deferens. These ducts appeared as hypoechogenic lines in all of the animals except the postmortem specimens. These lines helped to locate the area of the urethra that would be subsequently filled by emission.
Semen emitted into the pelvic urethra of the rhinoceroses in this study appeared to persist in the urethra for a longer period of time than reported in other species. In both electroejaculated and manually massaged rhinos, filling and emptying of the urethra took several minutes. In normal ejaculation by humans, the period is measured in seconds.
As long as semen was in the urethra of both massaged and electroejaculated rhinoceroses, penile massage stimulated clonic contractions of perineal musculature. This resulted in expulsion of fluid from the urethra, but filling did not reoccur. This suggested that penile massage may not be effective unless it is preceded by a technique that produces seminal emission. In this study, the electroejaculation and the conditioning of animals produced seminal emission before contact with the penis. Arousal may also produce seminal emission in the rhinoceros and thus be useful before penile massage. .Arousal has improved recovery of semen by manual massage from other species and has been recommended for the rhinoceros. The ability of techniques to produce seminal emission into the pelvic urethra could be investigated with ultrasonography.
A few drops of fluid were collected from unconditioned rhino 4 in this study, although fluid was not evident in the pelvic urethra. Other unconditioned rhinoceroses have produced small volumes from first attempts to collect semen from penile massage. The occurrence of sperm in these fluids may be the result of passive emission. Passive elimination may occur in the rhinoceros, as sperm has been collected in their urine. Also, nocturnal accumulation of semen was indicated when higher quality samples were collected in the morning before urination from manually massaged animals.
Ultrasonography indicated that manipulation of the reproductive tract may have improved the recovery of semen from electroejaculation. Samples collected by electroejaculation from these rhinoceroses were significantly greater in volume than previously reported.
Monitoring of semen in the pelvic urethra during electroejaculation may have resulted in the retrieval of semen from these rhinoceroses at the appropriate time. The pelvic urethra of these rhinoceroses filled during pauses between electrical stimulations. In these rhinos, several minutes were required to fill the urethra. The constraints of anesthesia of the rhinoceros typically result in rapid electroejaculation attempts with short rest periods and abrupt termination. Semen samples may be missed if they appear after stimulation and collection efforts have ceased. Also, longer periods of rest may be necessary to induce seminal emission into the pelvic urethra. However, a prolonged rest period may result in loss of semen, as semen remaining passively in the pelvic urethra may flow into the bladder. Immediate removal of semen from the urethra may be critical in preventing such loss.
Massage of both the rectum and the penis improved recovery of semen during electroejaculation. Rectal massage of reproductive organs has been suggested before stimulation by other methods in the bull and rhinoceros. In this study, semen was mechanically removed from the pelvic urethra after electroejaculation. The rhinoceros penis can be tightly retracted during electroejaculation, and the sigmoid curve may inhibit the release of semen. Encouraging the penis to straighten through massage may improve the release of semen from the pelvic urethra.

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