Preliminary Studies for Developing a Semen Importation Protocol to Increase the Genetic Diversity of the Captive Gerenuk Population
Gerenuk antelope (Litocranius walleri walleri) in US institutions are derived from a small group (n=28) introduced into the country 20 yr ago, of which ∼80% of the F1 generation were sired by one male. Intensive management is required to prevent inbreeding, but even so, infant mortality and disease susceptibility is high and certain genetic lineages have produced offspring with severe facial deformities and retinol colobomas, thus it is thought that the population would benefit from the introduction of new genes. Also, captive gerenuk ejaculates studied to date contain high proportions of morphologically abnormal sperm (45–94%; 1), that are partially attributable to age, but are not linked to seasonal effects. Previous studies in other species have linked semen quality and reproductive fitness with inbreeding. Gerenuk are relatively abundant in the wild, and preliminary studies show the heterozygosity of wild gerenuk (n=13; 0.714 haplotypes) is greater than that of captive gerenuk (n=26; 0.565 haplotypes). Retaining genetic diversity is a primary concern for species conservation. Assisted breeding techniques can augment the genetic management of a population by introducing new genes into a captive population without translocating animals. However, the practicalities involved in the concept of introducing genetic material from animals in range countries to individuals in captivity, have prevented these techniques from revolutionizing the captive management of closed populations.
For the past 4 yr we have studied the reproductive biology of the gerenuk; developing semen freezing protocols, using fecal hormone monitoring to determine estrus cycle length and developing estrus synchronization and artificial insemination (AI) protocols. These studies culminated in a pregnancy following AI with frozen-thawed sperm, though the calf was stillborn. Concomitantly, we have been involved in discussions with the U.S. Department of Agriculture (USDA) to develop a protocol outlining the necessary steps for importing semen from an African country. Earlier this year, we conducted a trial at the Ol Jogi ranch, Kenya and two wild gerenuk males were captured and safely maintained in temporary captivity for 44 days (the time specified by the USDA to fulfill quarantine requirements). Semen was successfully collected from both animals, revealing that higher numbers of morphologically normal spermatozoa and higher numbers of sperm/ejaculate were present in wild caught versus captive gerenuk. Upon release, both wild males were observed in their original territories, associated with their original gerenuk group. Blood samples collected from five different wild caught male gerenuk were tested at the USDA laboratory at Plum Island and all were negative for rinderpest, brucellosis, Rift Valley fever and foot and mouth disease. Four out of five samples were negative for bluetongue. These findings show that the importation of semen collected from wild caught gerenuk in Kenya, for use inseminating captive U.S. gerenuk, is an attainable goal.