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Type of publication: Journal Article
Type of document: Full Paper

Year: 2012

Authors: Hermes, R; Hildebrandt, TB; Walzer, C; Göritz, F; Gray, C; Niemuller, C; Schwarzenberger, F

Title: Estrus induction in white rhinoceros (Ceratotherium simum).

Source: Theriogenology. 2012; 78(6):1217-1223

Authors Vetmeduni Vienna:

Schwarzenberger Franz
Walzer Christian

Vetmed Research Units
Institute for Medical Biochemistry
Research Institute of Wildlife Ecology

The estrous cycle length in the white rhinoceros (Ceratotherium simum) is either 4 or 10 wk. The cause(s) for this variation as well as the poor fertility rate in captivity remains under debate in this species. Most captive adult white rhinoceros undergo long anovulatory periods without luteal activity which are considered a major reason for their low reproductive rate. In this study, the synthetic progestin chlormadinone acetate (CMA) was tested in combination with hCG or the GnRH analogue deslorelin for its efficiency to induce ovulation in fourteen females without luteal activity and in three, regular cycling females. HCG (N = 12), injectable GnRH analogue (N = 8) and GnRH analogue implants (N = 15) were given to induce ovulation after CMA treatment. Treatment success was determined using both transrectal ultrasonography and progesterone metabolite EIA analysis. A preovulatory sized follicle (3.5 ± 0.1 cm) or a corpus luteum (5.1 ± 0.7) was present on the ovary one day after induction in 93.1% of the treatments. Despite this high rate of ovarian response, ovulation rate differed between the study groups. The ovulation rate for hCG, injectable GnRH analogue and GnRH analogue implants was 66.7%, 62.5% and 93.3%, respectively. Ovulation rate in cyclic females treated with GnRH implants was 100% (6/6) compared with 89% (8/9) in females without luteal activity receiving the same treatment. The length of the estrous cycle when induced with hCG was 4 wk (85.7%). The estrous cycle when induced with GnRH analogue was predominantly 10 wk long. Two females without luteal activity treated with GnRH became pregnant. In conclusion, CMA in combination with GnRH analogue implants was highly effective to induce ovulation in white rhinoceroses and thus can contribute to efforts aimed at increasing natural mating and reproductive rates in the captive white rhinoceros population.

Keywords Pubmed: Animals
Chlormadinone Acetate/administration & dosage*
Chorionic Gonadotropin/administration & dosage
Drug Implants
Estrous Cycle/drug effects
Estrus/drug effects*
Estrus Synchronization/methods
Ovarian Follicle/ultrasonography
Ovulation Induction/methods
Ovulation Induction/veterinary*
Treatment Outcome
Triptorelin Pamoate/administration & dosage
Triptorelin Pamoate/analogs & derivatives

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