Contraception Used on Island Herds
ontraception is managing the population of wild horse herds on East Coast barrier islands. This method helps preserve the herds’ genetic heritage while controlling numbers in the absence of natural predators and diminishing vegetation, without interfering with the wild lifestyle of the animals.
A birth-control program was begun in January with 31 mares in the 100-member Shackleford Banks herd. The horses (they are now actually pony size) have developed largely isolated on their island home that is nine miles long and one mile wide in the Cape Lookout National Seashore of North Carolina.
PZP has also been used on horses for 13 years at Assateague Island National Seashore in Virginia. It’s manufactured from porcine (pig) zonae pellucidae (a membrane surrounding mammalian eggs) and stimulates the mare’s immune system to make antibodies that block fertilization. Mares that receive an initial dose only need a booster dose a month before breeding season to block fertilization for that year. It has no effect on developing fetuses or nursing foals, has little effect on social behavior, and is reversible.
Assateague studies have shown that contracepted mares live longer and carry more body weight since they get a break from the stress of nursing one foal while carrying another foal. PZP is delivered remotely with a dart by CO2 blowgun or a special .22 caliber rifle. Darts fall out and are recovered to confirm injection. Except for a momentary impact and a new wariness of humans bearing long tubes, the mares go on about the business of grazing.
Lethal White Syndrome
An all-white foal born to a Paint mare often dies within hours of birth, according to Dr. Kelli Cobler writing in Purdue (Ind.) University’s “Equine Health Update.” The gene that causes an all-white foal, when an overo mare is crossed with an overo stallion, also causes nerve cells not to develop in the lower part of the gut, and the foal can’t pass its first feces (meconium). The foal develops severe untreatable gas pain in a few hours.
The gene that causes Lethal White Syndrome has been discovered, and genetic testing can identify carriers. However, the test is not yet commercially available. The easiest way to prevent the disease is to cross an overo with a solid-color or tobiano horse. This makes the syndrome rare and still gives the breeder a 50 percent chance of producing an overo.
An overo is defined as having white markings on the belly extending upward but not over the back. They often have white faces. A tobiano has white marks starting on the back and extending downward. They also have white legs. These two types of Paint horses are genetically unrelated.
AQHA Silver Spur Award
The American Quarter Horse Association and MD Barns are sponsoring an award to recognize a Quarter Horse that has made a significant impact on the lives of others or who has spotlighted a positive image for the Quarter Horse breed. The deadline for nominations is August 1. The winner will be featured on a special segment of “GMC America’s Horse” on ESPN and receive a $20,000 MD Barns gift certificate. For further information: www.aqha.org.
EEE in California
EEE, which has never been diagnosed farther west than Texas, has caused the death of a 16-month-old horse in Ventura County, Calif. The horse had shown in Utah and California. Officials have no idea how the infection was introduced into the area.
California has had sporadic cases of St. Louis or Western equine encephalitis for decades. Officials are sufficiently concerned to have placed a flock of sentinel chickens in close proximity to the stable where the horse originated. Blood from the birds will be sampled at intervals for EEE antibodies to determine if infection is active in that area.
EEE has also been unusually active early in the season this year in Louisiana, where it is endemic. There are one confirmed and two suspected cases as of late May; close to 70 horses were found to be infected in 1999. EEE, like all types of viral encephalitis in horses, can also infect humans.
American Horse Publications announced its awards for 1999 on May 20, with Horse Journal being one of three magazines cited for General Excellence in the category of circulation over 15,000. Equus won the top award, with honorable mentions given to Horse Journal and Practical Horseman.
Horse Journal also won third place in the Service to the Reader category for “Drought ’99: Will It Affect Your Hay Prices’” and honorable mention in the Editorial category for “We Demand Answers.” Both were written by Dr. Eleanor M. Kellon.