Title page for ETD etd-05252012-102013


Document Type Master's Dissertation
Author Benavides Valades, Gabriela
Email gabeva@yahoo.com
URN etd-05252012-102013
Document Title Induction of anoestrus in free-ranging African elephant (Loxodonta africana) cows using a gonadotrophin-releasing hormone vaccine
Degree MSc
Department Production Animal Studies
Supervisor
Advisor Name Title
Prof M L Schulman Co-Supervisor
Dr H Anandale Committee Co-Chair
Dr H J Bertschinger Supervisor
Keywords
  • South Africa
  • Loxodonta africana
  • vaccine
  • African elephant cows
Date 2012-04-13
Availability unrestricted
Abstract
The GnRH vaccine may offer an alternative to the current immunocontraceptive method in elephant cows which uses native porcine zona pellucida proteins derived from abattoir slaughtered pigs as the immunogen, greatly limiting its availability. The pZP vaccine is stored at -20 °C and must be mixed with an adjuvant before use. The GnRH vaccine ImprovacŪ is commercially available, already contains the adjuvant and can be stored at 4 °C.

The aim of this study was to evaluate the efficacy of the gonadotrophin releasing hormone (GnRH) vaccine ImprovacŪ (Pfizer Animal Health, Sandton, South Africa) in the induction of anoestrus in elephant cows. The ImprovacŪ was administered to eight adult, female, healthy, free-ranging elephants, located in Entabeni Private Game Reserve in the Limpopo Province, South Africa. Another four cows were left untreated and served as controls.

The monitoring of the experimental population was conducted over a twelve-month observation period via non-invasive faecal steroid analysis. Progesterone metabolites in extracted samples were measured by Enzyme Immunoassay (EIA) to determine luteal activity and thus the effect of the GnRH vaccine on the endocrine correlates. This study started with a three-month control period prior to vaccination when faeces were collected from each study animal, as soon as possible after defecation to ensure positive identification of the individual with its sample. The three-month period was followed by the immunization protocol. The elephants all received a primary, followed by a booster vaccination dose five weeks later. Each dose of 3 ml contained 600 ėg of RnRF-protein conjugate; both treatments were applied via remote delivery. Monitoring continued until the end of the twelve-month observation period. Observations of oestrous behaviour during the twelve-month period were also recorded.

The results showed no statistical difference between treated and control females. There was, however, marked individual variation in response to GnRH immunization. This was possibly influenced by physiological and environmental factors such as age, where the youngest cows showed a better response in terms of reduced progestagen secretion; as well as season, where progestagen levels increased 1.3 times during the rainy season compared to the dry season. There was no association between average progestagen concentration and social hierarchy ranking. A high percentage (86.48%) of behaviours that could be related to oestrus coincided with the onset of the luteal phase and a subsequent rise in progestagen concentrations.

All the females (treated and control) showed some evidence of ovarian cyclicity during the study, although 75% of the cycles did not fall within the normal 13-17 week oestrous cycle range reported, suggesting that abnormal cycles are a common reproduction irregularity inherent to non-pregnant wild African elephants.

Further research to determine the optimal vaccination protocol is indicated in order to obtain consistent responses to the vaccine that will provide an efficient and safe contraceptive for use in female African elephants.

Copyright Đ 2011, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria

Please cite as follows:

Benavides Valades, G 2011, Induction of anoestrus in free-ranging African elephant (Loxodonta africana) cows using a gonadotrophin-releasing hormone vaccine, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-05252012-102013 / >

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