Ultrasonography of the urogenital tract in elephants (Loxodonta africana and Elephas maximus): An important tool for assessing male reproductive function

The success rate of captive elephant breeding programs worldwide is poor. A long with undiagnosed reproductive disorders in females and fatal diseases such as the newly discovered herpesvirus infection, male infertility now is considered a major contributing factor in the failure to maintain self-sus taining captive populations. To address questions related to male reproduct ive dysfunction, approximately 309 ultrasonographic assessments combined wi th semen collection were performed in captive (n = 10) and wild (n = 4) Afr ican (Loxodonta africana) and captive (n = 61) Asian (Elephas maximus) elep hants. Bulls ranged from 4 to 50 years of age and were examined at 9 instit utions in North America, 13 in Europe, 2 in Africa, and 7 in Asia. About ha lf of the reproductive assessments were performed in protected contact situ ations with elephants handled in a restraint device, and half involved asse ssments of trained Asian bulls managed in free contact. Four wild African a nd two Asian elephant bulls were evaluated after receiving general anesthes ia. Transrectal ultrasound was used to characterize the morphology and func tionality of the entire urogenital tract, including the testes and accessor y sex organs. Bulls were categorized on the basis of breeding status (breed ers vs. non-breeders) and social history (i.e., type of interaction with co nspecifics and keepers). Most of the bulls were non-breeders (designated Ty pes I-V). Type I (n = 3 African, 6 Asian) and Type V (n = 1 Asian) were imm ature and castrate, respectively. On the basis of keeper evaluations, Type II bulls (n = 2, 4) were subordinate to older cows and keepers, whereas Typ e LII bulls (n = 4, 28) were dominated by other bulls. Type TV (n = 1, 8) w ere older bulls of unknown history that exhibited numerous testicular patho logies resulting in poor semen quality. Non-breeding bulls included those t hat were exposed to females, but failed to breed, as well as these that had no opportunities to breed. Type VI individuals (n = 4, 14) were proven bre eders. The percentage of observable reproductive tract pathology in adult m ales was remarkably low (14%), even in older bulls. However, apparent infer tility of non-organic cause (i.e., not due to specific anatomical abnormali ties) in these otherwise healthy bulls was high (32%). Semen quality varied markedly in ejaculates collected from the same bull, as well as from diffe rent bulls. In conclusion, although many of these bulls could serve as seme n donors for natural mating or artificial insemination, the inconsistent pr oduction of good-quality ejaculates raises questions as to the reliability of these individuals to participate in breeding programs. The apparent inhi bitory effect of suppressive social interactions on reproductive potential also needs to be investigated. Ultrasound examinations combined with semen collection should be conducted periodically to estimate the reproductive va lue of each bull and determine whether altered management strategies are ne eded to enhance captive breeding. Zoo Biol 19:333-345, 2000. (C) 2000 Wiley -Liss, Inc.