Induction of the ovulatory LH surge in Asian elephants (Elephas maximus): a novel aid in captive breeding management of an endangered species

Abstract

A unique feature of the reproductive physiology of Asian elephants (Elephas maximus) is the occurrence of two LH surges before ovulation, instead of one. An anovulatory LH (anLH) surge, the function of which is unknown, occurs consistently 3 weeks before the ovulatory LH (ovLH) surge that induces ovulation. Thus, the ability to induce an ovLH surge would be useful for scheduling natural mating or artificial insemination. The present study tested the efficacy of a gonadotrophin-releasing hormone agonist (GnRH-Ag) to induce LH surges during the follicular phase of the oestrous cycle, which resulted in varied LH responses, but generally none were as high as previously documented natural surges. Thus, for the ovulation-induction trials, nine females were administered 80 microg GnRH-Ag intravenously at three time periods during the oestrous cycle, namely the anovulatory follicular phase, the ovulatory follicular phase and the luteal phase. During the late anovulatory follicular phase, nine of 10 females (90%) responded with an immediate LH surge followed 15-22 days later by an ovLH surge or a post-ovulatory increase in progestagens. In contrast, despite responding to the GnRH-Ag with an immediate increase in LH, none of the females treated during other periods of the oestrous cycle exhibited subsequent ovLH surges. One cow got pregnant from natural mating following the induced ovLH surge. In conclusion, ovLH induction is possible using a GnRH-Ag, but only during a specific time of the anovulatory follicular phase.

Role of the Double Luteinizing Hormone Peak, Luteinizing Follicles, and the Secretion of Inhibin for Dominant Follicle Selection in Asian Elephants (Elephas maximus)1

“…However, a second LH peak was only observed if the first peak was induced between Day 13 and Day 42 of the follicular phase. No second LH peak occurred when the GnRH agonist was administered between Day 9 and Day 12 [44]. We conclude that if the induced first LH peak occurred too early in the follicular phase, then the follicles of the first follicular wave were still too small and, therefore, did not luteinize.…”

“…The absence of LUFs and increased inhibin concentrations at the first compared to the second LH peak may furthermore explain why ovulation takes place only at the latter peak. A study performed by Thitaram et al [44], with the aim to induce the first LH peak, provides further evidence for the importance of LUFs as a source of inhibin. A gonadotropin-releasing hormone (GnRH) agonist administered to female Asian elephants during different time periods of the follicular phase always resulted in an immediate induction of a first LH peak.…”

Successful artificial insemination in the Asian elephant (Elephas maximus) using chilled and frozen-thawed semen

“…In addition to natural breeding, AI with either chilled or frozen-thawed semen will provide genetic diversity. Moreover, ovLH surge, which induced ovulation, induction protocol was developed [ 19 ]. This novel method is an important advance for AI [ 20 ], and is useful for reducing the labor and number of samples needed for identifying the anLH surge to time the assisted breeding 3 weeks later [ 3 ].…”

Differential testosterone response to GnRH-induced LH release before and after musth in adult Asian elephant (Elephas maximus) bulls

“…postmusth) GnRH challenge. The dose of GnRH selected was on the basis of what had previously been shown to stimulate the HPG axis in elephants [18,19]. Blood (5-7 mL) was collected from an ear vein at À15, 0, 30, 60, 90, and 180 minutes and 24 hours after GnRH administration via an indwelling catheter.…”