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Home / Equine Research Bank / Vaccines (Basel) / Immunocontraceptive Efficacy of Native Porcine Zona Pellucid...
Vaccines2024; 12(1); doi: 10.3390/vaccines12010096

Immunocontraceptive Efficacy of Native Porcine Zona Pellucida (pZP) Treatment of Nevada’s Virginia Range Free-Roaming Horse Population.

Abstract: In North America, range constraints due to burgeoning development increasingly encroach on wild horse habitat and necessitate effective but humane reproductive management. The largest free-roaming wild horse fertility control program by population (>3500) and territory size (≈300,000 acres) is located within Nevada's Virginia Range. Data from a field study investigated porcine zona pellucida (pZP) immunocontraception via remote dart delivery to mares in this population. Analyses aimed to measure efficacy by treatment effects on annual birth rates and population demographics and to evaluate treatment frequency and season against these variables. Analyses included mares' monthly data (January 2019-December 2022; 48 months), characterized by cumulative vaccination numbers subset into four classifications considering the vaccine as having no loss of efficacy or a loss within a 6-, 12-, and 18-month period post vaccination; from foaling data, the likelihood of being in foal and of conceiving in that month; and from age, as mature or immature (<1 years-old). A downward foaling rate and trend in the numbers of mature mares, descriptively presented at monthly intervals, showed markedly declining annual seasonal breeding peaks, with no observed change in foaling season or duration. Within four years, population coverage surpassed 70% and was associated with a 58% reduction in foaling, with only a 10% conception rate. Vaccinated mares increased proportionally: assuming a 12-month decay rate, the system reached stability at an average ≈1.0 vaccination/mare/year, providing a robust recommendation for treatment frequency contributing to best management practices.
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Publication Date: 2024-01-18 PubMed ID: 38250909PubMed Central: PMC10820100DOI: 10.3390/vaccines12010096Google Scholar: Lookup
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  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The study analyzes the use of Porcine Zona Pellucida (pZP) as a contraceptive in free-roaming wild horses in Nevada’s Virginia Range, showing that over four years, treatment resulted in a 58% reduction in foaling and gained 70% population coverage.

Research Objectives and Methodology

  • The study was conducted on the free-roaming wild horse population of Nevada’s Virginia Range.
  • One of the main objectives of the study was to investigate the efficacy of immunocontraception method using porcine zona pellucida (pZP) in managing the reproductive rate of these horses.
  • The pZP contraceptive treatment was delivered to mares via remote darting, a non-invasive method that does not require capturing or restraining the animals.
  • The effects of the treatment on annual birth rates and population demographics were examined, and the frequency of treatment was evaluated in relation to these variables.
  • Researchers recorded the monthly data of mares over a period of 48 months, from January 2019 to December 2022, to track changes in vaccination numbers, chances of pregnancy and conception, and demographic composition based on age.

Key Findings

  • The data showed a noticeable decrease in the foaling rate, indicating the contraceptive treatment was effective in controlling the population growth of the horses.
  • There was also a significant drop in the numbers of mature mares, leading to a decrease in the annual seasonal breeding peaks. However, the foaling season duration didn’t change.
  • After four years, the population coverage of the pZP treatment went beyond 70% of the overall horse population, resulting in a 58% reduction in foaling.
  • Furthermore, the conception rate decreased to 10%, suggesting a significant decline in fertility among the treated mares.

Implications of the Findings

  • Within the examined period, the ratio of vaccinated mares showed a steady increase.
  • The system indicated stability with an average of about one vaccination per mare per year, assuming a 12-month efficacy decay rate for the contraceptive.
  • These results provide practical insights for designing and implementing humane and effective fertility control programs, contributing to best management practices for wild, free-roaming horse populations in regions facing development-related constraints.

Cite This Article

APA
Schulman ML, Hayes NK, Wilson TA, Grewar JD. (2024). Immunocontraceptive Efficacy of Native Porcine Zona Pellucida (pZP) Treatment of Nevada’s Virginia Range Free-Roaming Horse Population. Vaccines (Basel), 12(1). https://doi.org/10.3390/vaccines12010096

Publication

Vaccines
ISSN: 2076-393X
NlmUniqueID: 101629355
Country: Switzerland
Language: English
Volume: 12
Issue: 1

Researcher Affiliations

Schulman, Martin L
  • Veterinary Population Management Laboratory, Faculty of Veterinary Science, University of Pretoria, Pretoria 0110, South Africa.
Hayes, Nicole K
  • American Wild Horse Campaign, Davis, CA 95617, USA.
Wilson, Tracy A
  • American Wild Horse Campaign, Davis, CA 95617, USA.
Grewar, John D
  • Veterinary Population Management Laboratory, Faculty of Veterinary Science, University of Pretoria, Pretoria 0110, South Africa.
  • JDATA, Sandbaai 7200, South Africa.

Grant Funding

  • Christine Stevens Wildlife Award $15 000.00 / Animal Welfare Institute

Conflict of Interest Statement

Two named authors of this manuscript, Nicole K. Hayes and Tracy A. Wilson, are employees of the funder, the American Wild Horse Campaign (AWHC), and during this employment actively engaged in various aspects of the research, design, data collection, data analysis and interpretation, manuscript preparation, and the decision to seek publication of this study. AWHC is a non-profit organization dedicated to preserving wild horses and burros in viable, free-roaming herds that are part of the United States of America’s national heritage. As a result, there is the potential for a perceived conflict of interest, which AWHC has addressed by taking the following steps: 1. Committing to full transparency in the research process, including disclosing the employment and involvement of named authors, as well as the organization’s mission; 2. Committing to make all data generated during the study available to the scientific community and the public for Independent scrutiny; 3. Acknowledging AWHC’s financial and logistical support for this research, at all relevant times.

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