Reproductive physiology and artificial insemination studies in wild and captive gerenuk (Litocranius walleri walleri)

Abstract

Gerenuk antelope in North American zoos are descended from 28 founders imported from Kenya ~20 years ago. Intensive management is required to prevent inbreeding depression. Artificial insemination has potential for augmenting genetic management, but successful application requires a thorough understanding of species' reproductive norms. Semen collected from captive (n = 10) and wild (n = 6) gerenuk contained low numbers of morphologically normal spermatozoa (~40%). Age, but not season, influenced (P < 0.05) the proportion of morphologically normal spermatozoa (mean � s.e.m., 12?17 months of age, 10.3 � 1.9%; 18?26 months of age, 34.4 � 6.2%; 3?6 years of age, 40.0 � 4.7%). Seasonality was investigated by analysing faecal testosterone and progesterone in males and females, respectively, by radioimmunoassays. Females cycled all year (ovarian cycle length, 18.7 � 0.9 days). Testosterone in males did not vary (P > 0.05) with time of year. Three females (3/9, 33%) became pregnant by insemination with 9.75?54.0 _ 106 motile fresh or frozen sperm after oestrus synchronisation with two prostaglandin F2? injections, 12 days apart. One female inseminated with frozen?thawed sperm delivered a full-term stillborn calf after 213 days gestation. These results characterise gerenuk reproductive norms and indicate that artificial insemination may be a useful tool in the genetic management of gerenuk.