Utilising routine non-invasive faecal samples for the detection of oestrus and early gestation in okapi (Okapi johnstoni)

Abstract

Zoos play a vital role in conservation with an overall aim of preserving species, such as the okapi (Okapi johnstoni), from extinction. To ensure species survival, sustainable ex-situ populations are required, and therefore understanding the reproductive status of individuals is important for population management. In this study, the oestrous cycles and gestations of four okapi (n = 7 pregnancies) were monitored through non-invasive faecal sampling methods to quantify progestagen and oestrogen metabolites. Baseline criteria for determining oestrous cycles was developed using approximately 20 months of sampling from each of two non-pregnant females, before being applied to pre- and early conception data. Pre-conception oestrous cycles were characterised in two females with luteal phase (mean ± SD) was 8.47 ± 1.41 days (n = 59) with an inter-luteal phase of 7.38 ± 1.67 days (n = 58), and overall average cycle length of 15.83 ± 2.02 days (n = 54 full cycles only). Observed in all four females, oestrogen metabolite peaks occurred at the beginning of the inter-luteal phase as progestagen metabolites were decreasing. Gestation was confirmed when progestagen metabolite concentrations remained at luteal phase concentrations for at least 20 days, with concentrations remaining at this level for the first 120 days of gestation without return to baseline values. A secondary increase at around 150 days lasted until parturition. These data demonstrate that okapi exhibit similar oestrous cycles to other members of the giraffidae family, with faecal oestrogens for the first time indicating that ovulation occurs at the beginning of the inter-luteal phase while progestagens are still elevated. Furthermore, we have shown that through routine sample collection and hormone monitoring, gestation can be confirmed within the first trimester, which can benefit the management of the species in ex-situ populations.

Keywords

• Ex-situ
• Progestagen
• Oestrogen
• Pregnancy
• Reproduction
• Management