Source: UNIVERSITY OF NEVADA submitted to NRP
LONG TERM CONTRACEPTION IN FERAL HORSE: EFFICACY, SAFETY AND BEHAVIOR
Sponsoring Institution
State Agricultural Experiment Station
Project Status
COMPLETE
Funding Source
Reporting Frequency
Annual
Accession No.
0204222
Grant No.
(N/A)
Cumulative Award Amt.
(N/A)
Proposal No.
(N/A)
Multistate No.
(N/A)
Project Start Date
Jul 1, 2005
Project End Date
Jun 30, 2008
Grant Year
(N/A)
Program Code
[(N/A)]- (N/A)
Recipient Organization
UNIVERSITY OF NEVADA
(N/A)
RENO,NV 89557
Performing Department
Ag Nutrition and Vet Sciences
Non Technical Summary
Population control of horses presents management difficulties as current techniques are expensive and not particularly effective. Contraceptive is a proposed alternative, but the efficacy and side-effects of long term contraceptive treatment has not been investigated. This project investigates the efficacy of contraceptive treatment as well as the behavioral side-effects of two different immunocontraceptive agents.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
13508301070100%
Knowledge Area
135 - Aquatic and Terrestrial Wildlife;

Subject Of Investigation
0830 - Wild animals;

Field Of Science
1070 - Ecology;
Goals / Objectives
This project falls into the greater project objectives of evaluating the efficacy and safety of contraceptive treatments for feral horse population control. The specific objective of this project is to: Evaluate the impact of PZP or GnRH immunocontraceptive vaccination on mare behavior (in captive feral and free-living feral mares), as well as impacts on stallion behavior and social group structure.
Project Methods
Specific hypotheses a) Treatment with a PZP vaccine will result in continued cycling throughout the breeding season, and that the continued cycling may change social dynamics between mares and within bands. b) Treatment with a GnRH vaccine will result in the cessation of all breeding behavior by mares. The absence of mating by stallions and mares may impact social dynamics within bands. c) Changes in social dynamics due to contraceptive treatment may change other aspects of behavior, such as band size or ranging behavior, which could influence the environmental impacts of feral horses. Research methodology The Nevada Department of Agriculture (NDOA) is responsible for a small herd of feral horses (950-1200 head) in an area around Virginia City, Nevada. These horses are not under the auspices of the Wild Horse and Burro Act and as such are not under federal government authority. NDOA is coordinating the experimental treatment of horses with the different contraceptive vaccines. Captive feral horses are being kept in the Carson City Correctional Facility. Contraceptives are given via deep intramuscular injection in the lateral muscles of the neck. Fifteen mares will be treated with each contraceptive and maintained in a group with 5 untreated mares and 4 stallions, which will be allowed to form into harem bands. In the field trial, ten feral mares will be assigned to each contraceptive treatment, as well as ten mares being identified as control mares. Horses are identifiable by their color variation and differences in their white markings on, particularly, their face and feet. Therefore, it should not be necessary to mark experimental individuals. Instead, identification photo files will be compiled. Contraceptives will be remotely delivered using a dartgun. Behavior of treated and control mares will be monitored from the treatment date for a period of three years. In addition, the behavior of the stallions in the bands containing control and treatment mares will also be monitored. Locations of these bands will be recorded to determine if ranging behavior changes after the mares first treated breeding season. Both the contraceptives result in mares carrying their current pregnancy to term and begin their effect in the subsequent reproductive cycle, enabling us to collect ranging behavior prior to and after the treatment effect. As the experiment proceeds, we will apply for funding to include more mares in the treatment in subsequent years.

Progress 07/01/05 to 06/30/08

Outputs
OUTPUTS: The contraceptive component of the field research is ongoing. Three years of data have been collected with plans for data collection in 2009. The behavioral component of the research was finished at the end of August 2007. A total of 307.4 hours of behavioral data were taken from January-August of 2007. These data were taken from 44 different bands and comprised of 71 different focal mares and 40 different stallions. From these bands, detailed behavioral data were collected, along with fecal samples and body condition scores. Efficacy data (foaling rates) were taken during the foaling season, and these data will continue to be taken in the spring of 2009. Currently, behavioral data are being transformed and analyzed and will be submitted for publication before the end of the year. Efficacy data are also being analyzed and written up. Several milestones took place with the lab component of research. Over 1100 fecal samples that were collected over the last 3 years were analyzed for hormones at the endocrinology lab at the St. Louis Zoo for both male and female adults. Females were tested for progesterone levels to determine cycling patterns and to assess pregnancy on females that were not seen with a foal. We also looked at how contraception may impact estrous cycles. Females were also tested for testosterone and estrodiol, to look at any impacts of contraception on these hormones. Males were tested for testosterone to detect any seasonal effects or changes due to the treatment status of females within the band. Selected males and females were tested for cortisol to see if any differences existed in stress levels based on contraceptive treatment. We also conducted an ACTH stimulation to verify the cortisol results. All of the fecal samples have been tested for hormones and these data are being analyzed. Progress was made on the genetics of the population and the PCR conditions were optimized for extracted fecal DNA. Only offspring need to be further analyzed and those data will be used to look at paternity and population genetics. This project is continued through NEV053BSA PARTICIPANTS: David Thain, Animal Biotechnology, UNR, Reno, Nevada Meeghan Gray, PhD student, UNR, Reno, Nevada Elissa Cameron, Associate Professor, Director, Mammal Research Institute, Department of Zoology & Entomology, University of Pretoria, Pretoria 0002, South Africa Phil Larussa, State Veterinarian, NV. Dept. of Agriculture (NDA), Reno, NV Michael Holmes, Virginia Range Estray Horse Manager, NDA, Carson City, NV Lowell Miller, USDA, APHIS, WLS, NWRL, Fort Collins, CO Gary Killian, USDA, APHIS, WLS, NWRL, Fort Collins, CO TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: This project is continued through NEV053BSA

Impacts
Reduction of free-ranging horses by limiting fertility holds the greatest promise for economic, humane and effective population control. Contraception in feral horses should be safe and potentially reversible, cost effective, efficacious for several years with minimal handling required, and should not affect normal reproductive and harem maintenance behavior. To date, reproductive control by injectable immunocontraceptive formulations, principally the PZP formulation, has not shown consistent effectiveness for more than 1-2 years, and involves much expense, manpower, and horse handling to maintain infertility. Long-acting contraceptive approaches are urgently needed for feral horse population control. This study will add significantly to the understanding of the behavior effects and duration of two different long-term immunocontraceptive products. Either product will potentially add an economical tool for range management of wild and feral horse populations.

Publications

  • No publications reported this period


Progress 01/01/07 to 12/31/07

Outputs
OUTPUTS: The contraceptive component of the field research is ongoing. Two years of data have been collected with plans for data collection in 2008 and 2009. The behavioral component of the research was finished at the end of August 2007. A total of 307.4 hours of behavioral data were taken from January-August of 2007. These data were taken from 44 different bands and comprised of 71 different focal mares and 40 different stallions. From these bands, detailed behavioral data were collected, along with fecal samples and body condition scores. Efficacy data (foaling rates) were taken during the foaling season, and these data will continue to be taken in the spring of 2008. Currently, behavioral data are being transformed and analyzed and will be submitted for publication before the end of the year. Efficacy data are also being analyzed and written up. Several milestones took place with the lab component of research. Over 1100 fecal samples that were collected over the last 3 years were analyzed for hormones at the endocrinology lab at the St. Louis Zoo for both male and female adults. Females were tested for progesterone levels to determine cycling patterns and to assess pregnancy on females that were not seen with a foal. We also looked at how contraception may impact estrous cycles. Females were also tested for testosterone and estrodial, to look at any impacts of contraception on these hormones. Males were tested for testosterone to detect any seasonal effects or changes due to the treatment status of females within the band. Selected males and females were tested for cortisol to see if any differences existed in stress levels based on contraceptive treatment. We also conducted an ACTH stimulation to verify the cortisol results. All of the fecal samples have been tested for hormones and these data are being analyzed. Progress was made on the genetics of the population and the PCR conditions were optimized for extracted fecal DNA. Only offspring need to be further analyzed and those data will be used to look at paternity and population genetics. PARTICIPANTS: David Thain, Animal Biotechnology, UNR, Reno, Nevada Meeghan Gray, PhD student, UNR, Reno, Nevada Elissa Cameron, Associate Professor, Director, Mammal Research Institute, Department of Zoology & Entomology, University of Pretoria, Pretoria 0002, South Africa Phil Larussa, State Veterinarian, NV. Dept. of Agriculture (NDA), Reno, NV Michael Holmes, Virginia Range Estray Horse Manager, NDA, Carson City, NV Lowell Miller, USDA, APHIS, WLS, NWRL, Fort Collins, CO Gary Killian, USDA, APHIS, WLS, NWRL, Fort Collins, CO

Impacts
Reduction of free-ranging horses by limiting fertility holds the greatest promise for economic, humane and effective population control. Contraception in feral horses should be safe and potentially reversible, cost effective, efficacious for several years with minimal handling required, and should not affect normal reproductive and harem maintenance behavior. To date, reproductive control by injectable immunocontraceptive formulations, principally the PZP formulation, has not shown consistent effectiveness for more than 1-2 years, and involves much expense, manpower, and horse handling to maintain infertility. Long-acting contraceptive approaches are urgently needed for feral horse population control. This study will add significantly to the understanding of the behavior effects and duration of two different long-term immunocontraceptive products. Either product will potentially add an economical tool for range management of wild and feral horse populations.

Publications

  • No publications reported this period


Progress 01/01/06 to 12/31/06

Outputs
Behavioral Results We have continued to monitor 47 different bands that range in total size from 3 members to 11 members, and within which our 93 focal mares are located. The PhD student is currently observer horses every day from sunrise until sundown. The same behavioral measures are being taken which include aggressions, affiliations, approaches and leaves, sexual interactions, maternal behavior, and spatial distancing. Bands were also monitored for band membership, deaths and births. These behavioral data collected will be collected until the end of the year and used to determine differences in social interactions with treated mares versus control mares and to detect differences between PZP and GnRH. Only 5 of the original GnRH-treated mares are left in the population due to management problems. These mares continue to behave more submissively than controls and continue to shift band membership. Due to the fact that the observer is blind to the treatments and this study is a long term behavior study, conclusions based on behavioral observations will not be known until the end of 2007 when field work is concluded. We expect to publish several papers relating to management, social structure, courtship behavior, and maternal behavior. Population Results Only one of the original 8 GnRH-treated mares foaled in 2005 and none of the remaining mares foaled in 2006. These preliminary results indicate that GnRH has efficacy rates similar to PZP products and can be useful to decrease pregnancy and foaling rates. The overall efficacy rates from 2006 gave surprising results. While both control groups had foaling rates around 50%, the GnRH mares and one of the PZP groups foaled at about half the control rates. However, the other PZP groups showed a significant increase in foaling rates compared to controls; appearing to increase fertility. These are the first efficacy results comparing both GnRH and PZP products, and we plan to publish the overall results after the 2007 foaling season. There are also several mares from 2006 in which their pregnancy and possible foaling was unknown. Genetic Results Blood samples collected from the original round-up have been successfully genetically tested in the laboratory. We utilized 13 horse-specific polymorphic microsatellite loci that we validated in our lab and determined allelic and genotypic designation using the ABI GeneMapper 3.7 software of over 200 horses in our study population. Initial results indicate that the population is much more heterozygous than expected and the 13 polymorphic loci will allow us to determine the paternity of every foal born in the population by using a parentage likelihood analysis for each foal, which determines the most likely father. We will use fecal samples to get DNA from the rest of the horses from which we did not obtain a blood sample (i.e. new foals, juveniles, bachelor males, males that takeover bands). We have already successfully extracted DNA from fecal samples and have developed a new approach to improving DNA extraction, from which we expect a methods paper by the end of 2007.

Impacts
At the completion of this study, significant information on the herd behavioral effects of two contraceptive modalities will be evaluated. This will contribute to the knowledge base of the use of GnRh and PZP products for field managers of wild and feral horse populations.

Publications

  • No publications reported this period


Progress 01/01/05 to 12/31/05

Outputs
The project continues to progress well, with many milestones accomplished in 2005. In June 2005, horses were gathered by a helicopter round-up and a total of 93 mares were treated with a contraceptive (2 types, PZP or GnRH agonist) or a control (2 types, adjuvant only, or no treatment). Mares were treated in a systematic order, allowing some bands to have all treated mares, some treated mares, or only control mares. At the time of treatment, mares had blood samples taken, were aged by tooth wear, and permanently freeze-branded. Mares varied in age from yearling to >20 years old. Behavioral data collection and fecal sampling started right after treatment of mares and continues to be ongoing. The field observer is blind to the treatment given to each focal mare. Since the time of treatment, we have continued to monitor 47 different bands that range in total size from 3 to 11 members, within which our 93 focal mares are located. The PhD student is currently observing horses 5 days a week from sunrise until sundown. These field methods are used to determine how contraception changes the behavior of feral horses and are the same methods developed in our first year of research. The study is a long term behavioral study, and the majority of mares were only treated in 2005. Therefore, we will not have our results until next year, but we continue to monitor and document behavior in the horses, and have collected a substantial amount of data to date. However, we have preliminary data on a subset of mares treated in March of 2004, in which a small sample (n=8) of free-roaming mares were treated with GnRH agonist contraceptive. Out of the other 7 treated mares, only one mare had a foal in the 2005 season, while the rest were not observed to be pregnant, nor having a foal. Conversely, each of the 8 control mares foaled in the 2005 season. Preliminary behavioral data from 8 mares treated with GnRH in 2004 suggests that GnRH treated mares may become more submissive during aggressive interactions. Control mares on average were more aggressive towards other band members than GnRH treated mares (t14=2.845, p<0.05). In addition, GnRH treated mares received more aggressions from other band members as compared to control mares (t14=2.262, p<0.05). Our preliminary data indicates that GnRH treated mares behave differently than control mares with respect to the levels of aggressions received and directed towards each mare. Five out of the 8 GnRH treated mares have been observed copulating with band stallions and bachelors, which is surprising since this contraception formulation causes the cessation of cycling hormones and cycling itself. In addition, 2 treated mares have permanently switched from bands they resided in at the time of treatment. Two other treated mares have left their bands, but returned. No control mares changed bands either temporarily or permanently during the same period. These preliminary data suggest that GnRH contraceptive treatment may impact normal behavior and suggests that behavioral data needs to continue to be collected for our increased sample size of contraceptive treated mares.

Impacts
Reduction of free-ranging horses by limiting fertility holds the greatest promise for economic, humane and effective population control. Contraception in feral horses should be safe and potentially reversible, cost effective, efficacious for several years with minimal handling required, and should not affect normal reproductive and harem maintenance behavior. To date, reproductive control by injectable immunocontraceptive formulations, principally the PZP formulation, has not shown consistent effectiveness for more than 1-2 years, and involves much expense, manpower, and horse handling to maintain infertility. Long-acting contraceptive approaches are urgently needed for feral horse population control. This study will add significantly to the understanding of the behavior effects and duration of two different long-term immunocontraceptive products. Either product will potentially add an economical tool for range management of wild and feral horse populations.

Publications

  • No publications reported this period