Table of Contents
Journal of Vaccines
Volume 2013, Article ID 181834, 7 pages
Research Article

Effects of a Commercial Canine Gonadotropin Releasing Hormone Vaccination on Intact Male Llamas and Alpacas

1Department of Animal and Rangeland Sciences, Oregon State University, Corvallis, OR 97331, USA
2College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331, USA
3Battelle Toxicology Northwest, Richland, WA 99352, USA
4Animal Health Diagnostic Center, Endocrinology Laboratory, Cornell University, Ithaca, NY 14853, USA

Received 18 December 2012; Accepted 19 February 2013

Academic Editor: Phillip R. Pittman

Copyright © 2013 C. E. Donovan et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We have investigated the effect of immunization against gonadotropin releasing hormone (GnRH) using a commercial canine GnRH vaccine on testosterone concentration, testicular volume, testicular histology, and intermale behavior in intact male llamas and alpacas. Llamas ( ) and alpacas ( ) were either immunized (received 3 mL of vaccine given intramuscularly) or treated as controls (received 3 mL of sterile diluent given intramuscularly) at 0, 3, and 6 weeks. Blood samples and testicular volume measurements were taken at 0, 3, 6, 9, and 12 weeks. Owner surveys grading behavior at 0 and 12 weeks were received for 14 llamas. Two llamas at each time point undergoing the vaccination procedure were also castrated for testicular histological examination. Vaccinated animals elicited a GnRH antibody titer, and there was a significant decrease in testosterone concentration and testicular volume when compared with control animals. Intermale aggressive behavior was also significantly decreased in the surveyed llamas. However, histological examination revealed no significant changes. GnRH immunization using the canine GnRH vaccine may be an effective method for reducing intermale aggression in llamas and alpacas by decreasing circulating testosterone concentrations but cannot be recommended as an immunosterilant because of its lack of efficacy in interrupting spermatogenesis.