Reproductive assessment of male elephants (Loxodonta africana and Elephas maximus) by ultrasonography.

Transrectal ultrasonography was performed on five wild and two captive male African elephants (Loxodonta africana) and four captive male Asian elephants (Elephas maximus) to develop standards for assessment of reproductive health and status. The entire internal urogenital tract was visualized ultrasonographically by using a 3.5 MHz or a 7.5-MHz transducer in combination with a probe extension adapted for elephant anatomy. The findings were verified by postmortem ex situ ultrasound examinations in several individuals of each species. Each part of the internal urogenital tract was sonographically detectable except for the bulbourethral glands and the cranial portion of the ureters and ductus deferentes, which were only observed in situ in the neonate. Each structure visualized was measured and described. The size and morphology of the urogenital structures, especially the accessory glands, were indicative of breeding status, if known. There was a notable difference between African and Asian males in the size and morphology of the prostate gland and a slight difference in the shape of the ampullae. No other structure showed significant species differences. The detection of the location and description of the testes may provide information for modifying present castration procedures. Furthermore, ultrasound examination of the male accessory glands may aid in the identification of potential semen donors for assisted reproduction programs in captive elephants.