Research: Liquid Semen Storage in Elephants

/ / / Research: Liquid Semen Storage in Elephants

Liquid Semen Storage in Elephants (Elephas maximus and Loxodonta Africana): Species Differences and Storage Optimization

Artificial insemination (AI) plays a key role in genetic management of elephants in captivity. Currently, freshly extended or chilled semen is used in all AI attempts. To maximize AI efficiency, it has become imperative to optimize conditions for liquid storage and semen transport. The objectives of this study were to examine the interactions between different extenders and storage temperature on sperm total motility (%tMOT), progressive motility (%pMOT), and acrosomal integrity (%INT) in Asian (Elephas maximus) and African (Loxodonta africana) elephants. Ejaculates were collected by rectal massage and diluted using a split-sample technique in five semen extenders TL-Hepes (HEP), Modena (MOD), Biladyl (BIL), TEST Refrigeration Medium (TES), and INRA96 (INR) and stored at three different temperatures (35°C, 22°C, and 4°C). At 0, 4, 6, 12, and 24 h, aliquots were removed and assessed for %tMOT, %pMOT, and %INT. After 24 h of storage, African elephant spermatozoa exhibited greater longevity and higher values in sperm quality parameters compared to Asian elephants. In both species, semen storage at 35°C resulted in a shape decline in all sperm quality parameters after 4 h of storage, while storage at 22°C and 4°C facilitated sperm survival. In Asian elephants, MOD and HEP were most detrimental while BIL, TES, and INR maintained sperm motility up to 12 h when cooled to 22°C or 4°C. In African elephants, there were no differences among extenders. However, MOD, BIL, and INR were most effective at lower temperatures, while HEP and TES maintained sperm motility at all storage temperatures. In conclusion, liquid storage of Asian elephant sperm was most efficient in BIL, TES, and INR at 22°C or 4°C. In contrast, semen from African elephants maintained sperm parameters in all media at 22°C or 4°C. This clearly demonstrates species-specific differences in storage sensitivities between Asian and African elephant spermatozoa and recommends media choices for liquid storage.

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Elephant Endothelial Cells: A System to Isolate Elephant Endotheliotropic Herpesvirus

PROGRESS UPDATE: Elephant endotheliotropic herpesviruses (EEHVs) are a leading cause of reproductive failure and neonatal and juvenile deaths in Asian elephants. These viruses kill young elephants and thwart efforts to maintain a self-sustaining captive population. To address this problem, scientists at Cornell University are investigating ways to isolate the virus in the lab in cultured elephant endothelial cells (cells that line the blood vessels). The ability to isolate EEHV in cell cultures is crucial to provide the tools necessary to study disease mechanisms, including how EEHV infects animals and which animals might be susceptible to fatal infection or resistant to the virus’s effects. For the first time, scientists have isolated endothelial cells from elephant umbilical cords and established an endothelial cell culture system for propagation of EEHV. The scientists have shared the technology with other laboratories in the United States and Europe, establishing an international collaboration to further refine the elephant endothelial cell culture technique and isolate EEHV. Once established, an in vitro endothelial cell culture system capable of propagating EEHV can be used to test types and doses of antiviral medications and thereby improve treatments for EEHV-infected elephants. This in vitro system will also become a valuable tool in the future development of an effective and safe vaccine that will benefit elephants worldwide.

Elephant Endotheliotropic Herpesvirus Research

Infectious disease is one of the factors threatening the long-term survival of Asian and African elephants. EEHV can be a fatal disease of elephants in human care and in the wild, and is one of the many conditions which can impact the overall health and survivability of elephants. Young elephants are most vulnerable to EEHV, making it a particularly devastating disease. Reproductive failures and early deaths of juvenile elephants in North America and Europe have been attributed to EEHV, and EEHV has been confirmed as the cause of death in up to ten wild elephants in India, Thailand and Cambodia including both orphaned and free-ranging calves

[Reid et al 2006; Zachariah et al, IEF Conservation & Research Symposium conference abstracts Bangkok 2008, Pretoria 2010]. It is not known if there have been widespread outbreaks in Asia; however the impact of EEHV may now be exacerbated by increased fragmentation of elephant populations. Little is known regarding basic epidemiology of this virus, such as transmission patterns, incubation period, site, and cell tropism for viral latency.

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Luteogenesis during the estrous cycle in Asian elephants (Elephas maximus)
Dr. Imke Lueders

The occurrence of multiple corpora lutea (CLs) in the ovaries of the cycling and pregnant elephant, a monovulatory mammal, has driven scientific discussions during the past five decades. However, fundamental knowledge on luteogenesis is lacking. In this long-term study, CL formation and regression throughout the estrous cycle were monitored using transrectal 2D- and 3D ultrasonography in 33 captive Asian elephants. Serum or urinary progestagens (Pm) were measured to determine the reproductive cycle stage. In seven females, serum Pm and LH concentrations were directly related to ovarian events.We have found two different modalities of luteal development: one for the accessory CL (acCL) and one for the ovulatory CL (ovCL). acCLs were derived from luteinization of larger, subordinate follicles after the first anovulatory LH peak. The dominant follicle produced the largest CL after the second (ovulatory) LH peak. The first luteal tissue formation became visible w10 days after the respective LH peak. After ovulation, it took 29.8G5.0 days for the acCLs to reach their maximum diameter, whereas the ovCL reached a significantly larger size (33.2G2.3 mm, P!0.0001) about 10–15 days later. All CLs were visible throughout the new follicular phase, with some of the larger ones still present in the subsequent luteal period. In this study, we have demonstrated that Asian elephants have evolved a novel method for luteal development and function, and by repeatedly forming two types of distinctly different CLs for every reproductive cycle, they have ensured that there will be sufficient luteal capacity for maintaining a 22-month pregnancy should conception occur.
Reproduction (2010) 140: 777–786