Ultrasonographic characterization of ovarian events and fetal gestational parameters in two southern black rhinoceros ( [formula omitted][formula omitted][formula omitted]) and correlation to fecal progesterone

• Published in: Theriogenology Vol. 55; no. 5; pp. 1033 - 1049
• Main Authors: Radcliffe, R.W., Eyres, A.I., Patton, M.L., Czekala, N.M., Emslie, R.H.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15.03.2001
• Subjects: [formula omitted][formula omitted]; Animals; black rhinoceros; Conservation of Natural Resources; Embryonic and Fetal Development - physiology; estrous cycle; Estrus - physiology; Eye - diagnostic imaging; Eye - embryology; Feces - chemistry; Female; Gestational Age; Hoof and Claw - diagnostic imaging; Hoof and Claw - embryology; Male; Ovarian Follicle - diagnostic imaging; Ovarian Follicle - physiology; Ovulation Detection - methods; Ovulation Detection - veterinary; Perissodactyla - physiology; Pregnancy; Progesterone - analysis; reproduction; Sex Determination Analysis - methods; Sex Determination Analysis - veterinary; Ultrasonography, Prenatal - veterinary; estrous cycle; black rhinoceros; Diceros bicornis; pregnancy; reproduction
• DOI: 10.1016/S0093-691X(01)00464-2
• ISSN: 0093-691X

A tremendous potential exists for the application of transrectal ultrasonography as a tool to enhance the captive management of endangered species. Reproductive study of two southern black rhinoceros ( Diceros bicornis minor ) females was performed daily to every other day for a ∼60 day period to document ovarian changes, and three times weekly in early pregnancy to once monthly in late pregnancy in order to characterize changes in fetal parameters throughout gestation. All ovarian and fetal anatomical structures were measured in millimeters. The mean (+/− SD) length of the estrous cycle or interovulatory period was 26 +/− 1.4 days (n=2 cycles). Follicular growth rate of a dominant follicles was ∼3 mm/day once the follicle reached 35 mm in diameter. Ovulation was observed to occur at a mean (+/− SD) follicular diameter of 49.5 +/− 2.6 mm (n=4) and within 48 to 72 h after observed estrus (n=2). Large ovarian structures [mean (+/− SD) diameter of 71.7 +/− 2.9 mm; n=3], considered analogous to equine anovulatory hemorrhagic follicles, were observed to form in the winter months and suggest seasonal periods of reduced fertility. Fecal progesterone assays confirmed ultrasonographic events. Although preliminary, the results of fetal sexing are presented and compared to the horse. Our data indicate that fetal eye or fetal foot diameter measurements can be used to accurately predict gestational age from about 2 months to term, providing useful information to managers of both captive and wild rhino populations. The ability to identify and quickly release animals in late term pregnancy in the wild and thereby reduce abortions and neonatal mortalities in holding bomas is one potential practical conservation benefit of the fetal are predictive models.