Reproductive endocrine monitoring of elephants: An essential tool for assisting captive management

Abstract

Considerable information now is available about the basic reproductive biology of elephants, especially females. However, as important as this knowledge is, it no longer is enough to simply compile it into a database. The potential exists for using endocrine monitoring techniques to solve real problems. This review summarizes our current knowledge of elephant endocrinology and offers suggestions on how to use the technology to maximize reproductive potential. The estrous cycle can be monitored through the analysis of serum progestogens, primarily 5α‐reduced compounds, and consists of an 8‐ to 12‐week luteal phase and a 4‐ to 6‐week inter‐luteal period. Proof of ovarian cyclicity currently is mandatory before Species Survival Plan breeding recommendations are approved. However, because many adult females are not cycling normally, the reproductive monitoring of all cows throughout their life span is now encouraged. Complete endocrine evaluations in conjunction with ultrasound examinations and behavioral assessments are needed to identify causes of reproductive failure and develop mitigating treatments. Progestogen analyses also are effective for monitoring pregnancy, but only if longitudinal samples are collected. Alternatively, pregnancy can be diagnosed in occasional samples using serum prolactin or possibly relaxin measurements after 20 weeks of gestation. Parturition can be predicted on the basis of the rapid decrease in progestogens that occurs about 2–5 days before birth. An updated model of ovarian dynamics during the estrous cycle suggests that two waves of follicular development occur 3 weeks apart during the non‐luteal phase, possibly under the control of follicle‐stimulating hormone. Each follicular wave culminates in a luteinizing hormone (LH) surge, with the second surge inducing ovulation and corpus luteum formation. The functional significance of the first, anovulatory LH surge is under investigation, but from a practical perspective it can be used to schedule breeding (by artificial insemination or natural mating) to coincide with the ovulatory LH surge. Less is known about the reproductive biology of bulls, aside from the fact that musth is associated with dramatic changes in androgen secretion. Studies are needed to determine whether poor libido and inadequate semen quality observed in some mature elephants are due to testicular steroidogenic dysfunction. When blood samples cannot be collected for routine hormone analysis, gonadal activity can be monitored non‐invasively through the measurement of excreted steroid metabolites (males: androgens; females: estrogens, progestogens) in urine and feces. Lastly, suggestions for future research priorities are provided. Zoo Biol 19:347–367, 2000. © 2000 Wiley‐Liss, Inc.

Fecal 20-oxo-pregnane concentrations in free-ranging African elephants (Loxodonta africana) treated with porcine zona pellucida vaccine

“…Phase length estimates as well as ovarian cycle length estimates are given as mean ± SD. Females were categorized as having an irregular cycle when overall cycle length exceeded or fell short of the reported norm of 13 to 17 weeks [10,[17][18][19][20][21][22][23][24][25]. The non-cycling category was reserved for females who had no identifiable pattern in 5-pregnan-3-ol-20-on concentrations throughout the study period [46].…”

“…In the female African elephant (Loxodonta africana), estrous cycle length is reported to range between 13 to 17 weeks [17][18][19][20][21][22][23][24][25]. The cycle is divided into a 4 to 6 week follicular phase after 4 which an increase in progesterone levels, believed to trigger ovulation, marks the onset of an 8 to 11 week luteal phase [17,[20][21][22].…”

Assessment of luteinizing hormone and prolactin immunoactivity in Asian and African elephant urine using assays validated for serum

“…Much has been learned about the reproductive endocrinology of elephants in the past decade, and this has contributed significantly to improved breeding management (see reviews, Hodges, 1998;Brown, 2000Brown, , 2006. While most of the initial work was based on analyses of circulating hormones, more recent studies have shown the utility of urine and faecal steroid metabolite assessments for noninvasive monitoring of gonadal function in the elephant (Heistermann et al, 1997;Fiess et al, 1999;Czekala et al, 2003).…”

“…Another hormonal indicator is a marked increase in prolactin immunoactivity after 5 months of gestation (Brown, 2000(Brown, , 2006. The diagnostic advantage of prolactin is that only a single sample is needed after 5 months, compared to the longitudinal sampling that is necessary for pregnancy diagnosis with progestagens.…”

“…The diagnostic advantage of prolactin is that only a single sample is needed after 5 months, compared to the longitudinal sampling that is necessary for pregnancy diagnosis with progestagens. Whereas progestagens can be measured in blood, urine and faeces, LH and prolactin have only been quantified in blood (Brown, 2000), and as such are impractical assessment tools for elephants that are not trained for routine blood collection or are free-ranging. This is especially true for LH, because characterizing the double surge requires daily blood sampling throughout most of the follicular phase.…”