Horse owners who transport their animals internationally for equestrian competitions may soon have an easier time ensuring their horses are healthy, thanks to new ARS-developed tests for piroplasmosis. The United States is free of this tickborne disease, also known as equine babesiosis. To keep the disease from infecting American animals, horses coming here for races, shows, and other competitions must be certified free of the disease. That can be costly, because horses must be quarantined while they are awaiting test results and often must be retested to ensure accurate results. In addition, American horses traveling to other countries that have piroplasmosis must be tested before they can return. The new tests—one for each of the two parasites that can cause the disease—should speed up the process once they are accepted as appropriate by international regulatory authorities. The current test, called a complement fixation test, can give false positive or false negative readings. The new tests rely on molecular techniques that give more accurate results. Another advantage: The new tests do not require the use of live horses. Genetic material used in the new tests can be grown in bacteria. The complement fixation test relies on obtaining parasites and blood with antibodies from infected animals. ARS and Washington State University collaborators have applied for patents. VMRD, a Washington company that produces diagnostic test kits, plans to sell the tests under a patent license within the next 5 years.

Animal Disease Research Unit, Pullman, WA
Donald Knowles, (509) 335-6022, dknowles@vetmed.wsu.edu

By scrutinizing the chromosomes that store cow DNA, ARS animal scientists are helping lay the groundwork for a genetic roadmap of the animal’s traits. It may be years before such a map is finished, but some short-term spinoffs are emerging. One possibility is a genetic test to predict the degree to which newborn calves will express traits inherited from a prized bull. It now takes 5 years before a dairy calf’s traits can be fully evaluated. However, using specific stretches of DNA chemicals called nucleotides as markers, scientists envision tests for making such predictions much sooner—either from a few embryonic cell samples, or from a blood sample from a newborn calf. In genetic mapping studies, scientists use the markers to locate DNA regions where important genes are found. On chromosome 27, for example, they’ve identified potential markers for “dairy form,” a trait for the ideal physique in cows. Another marker, on chromosome 23, may point to genes’ influencing a cow’s response to mastitis, an udder disease that costs the dairy industry $1 billion annually in losses. Also of interest are markers for unknown genes that will lead to enriched dairy products and improved cheesemaking.

Gene Evaluation and Mapping Research Laboratory, Beltsville, MD
Melissa Ashwell, (301) 504-8543, mashwell@ggpl.arsusda.gov

GT-HID9, a new germplasm source of yellow dent maize, could mean good news for Southeastern dairy farmers in the form of new commercial hybrids. ARS and University of Georgia researchers released the maize germplasm to plant breeders for two key traits: adaptability to the Coastal Plain’s sandy/loam soils and warm southern climate, and suitability as corn silage that milking cows can readily digest. Currently, few such hybrids are available to dairy farmers in Southeastern States like Georgia, where 95 percent of the Coastal Plain’s corn crop is grown. Now, with the release of GT-HID9 seed to plant breeders, new silage hybrids may become commercially available within 6 years. GT-HID9 is the product of nearly 10 years of work involving a technique called restricted recurrent phenotypic selection. From an older hybrid, Coker 77B, researchers propagated and screened thousands of plants for silage/forage traits with high dry-matter digestibility. With the help of in vitro studies using cow rumen, they zeroed in on GT-HID9, a plant population whose digestibility ranking exceeds Coker 77B’s by more than 1 percent. In the cow’s rumen, where a microbial slurry digests fiber, this seemingly low percentage actually means significant increases in absorption and use of nutrients from silage for producing milk.

Crop Genetics and Breeding Research Unit, Tifton, GA
Neil Widstrom, (912) 387-2341, nwidstro@tifton.cpes.peachnet.edu
Roger Gates, (912) 386-3187, rngates@tifton.cpes.peachnet.edu

Beekeepers who want to replace aggressive, defensive African queens with gentle, easily managed European ones may face a little-known disadvantage, an ARS scientist and University of North Carolina co-researcher have discovered. Within only 1 week after their queen dies or is removed by beekeepers, Africanized worker bees—which are female—can produce their own viable eggs for requeening the hive. That gives the Africanized bees a headstart in the battle for hive rule, because European worker bees’ ovaries can’t start producing eggs until the queen has been missing for at least 3 weeks. Queenless Africanized workers that have developed ovaries and are laying their own eggs are less likely to accept a new European queen—and may attack and kill her. New experiments, however, may yield tactics to undermine the Africanized bees’ competitive advantage. The 1-week time frame was already known to occur in Cape bees of South Africa, but it had not—until now—been reported for Africanized hives in the Northern Hemisphere. Africanized bees, which sting more readily then their European counterparts, have invaded Arizona, California, Texas, New Mexico, and Nevada.

ARS Carl Hayden Bee Research Center, Tucson, AZ
Gloria DeGrandi-Hoffman, (520) 670-6380, ext. 105, gdhoff@aol.com

Canola grown on soils high in selenium or irrigated with water that’s overloaded with this mineral may boost the health of livestock—and the environment. Animals and people require small quantities of selenium to stay healthy. But in high amounts, it can become a toxic contaminant of soil and water. With further testing, canola plants used to remove excess selenium from soil or water might then be fed to farm animals to ensure they get enough of this essential nutrient. Right now, selenium deficiency is a major problem for livestock or wildlife in at least 37 states and costs beef, dairy, sheep, and horse producers an estimated $545 million in losses every year. Ranchers in regions where soil is low in selenium either inject their livestock with the mineral or provide selenium supplements to the animals. In a preliminary study, ARS scientists fed selenium-enriched canola hay to lambs and dairy cattle, then monitored levels in the blood, milk and other samples. The researchers used canola that irrigated with high-selenium drainage water. Selenium content of the canola didn’t exceed a safe level—the equivalent of about a pinch of selenium per bale of hay, or 5 milligrams per kilogram of dry matter. All of the animals remained healthy throughout the study. The experiment was likely the first to use—as an animal feed or supplement—canola that had been grown to remove selenium from soil. Follow-up tests may determine whether this approach to enhancing the selenium content of livestock feed is a safe way to forestall selenium deficiency.

Water Management Research Unit, Fresno, CA
Gary S. Bañuelos (559) 453-3115, banuelos@asrr.arsusda.gov
Northwest Irrigation and Soils Research Laboratory, Kimberly, ID
Henry F. Mayland, (208) 423-6517, mayland@kimberly.ars.pn.usbr.gov

New strides in ascites research could help prevent this fatal heart condition in chickens. Ascites can cost U.S. poultry producers $100 million a year. When a chicken gets it, the right ventricle of its heart enlarges and can’t pump blood efficiently, eventually leading to death. It takes just 6 weeks for birds to grow large enough to go to market, and their hearts and lungs have to work hard to accommodate this rapid growth pace. Some birds’ bodies can’t keep up, leading to ascites. Often, birds raised at high altitudes develop this condition. ARS researchers used a special chamber to simulate higher altitudes and the occurrence of ascites. They then identified and selectively bred ascites-resistant and ascites-susceptible birds. In the fourth year of the study, ARS and University of Arkansas scientists have selected over four generations for broilers that are resistant or highly susceptible to this disease. The resistant population exhibits no more than 20 percent ascites at simulated high altitudes, while the susceptible line has greater than 80 percent. To control ascites, producers now restrict feed, which slows down birds’ growth and reduces mortality. But these birds take longer to reach market weight and can have less white meat, the most valuable part of the chicken. ARS researchers suggest that poultry producers maintain optimal temperatures or increase ventilation in their poultry houses to improve air quality and reduce the incidence of ascites.

Poultry Production and Product Safety Research Unit, Fayetteville, AR
Janice M. Balog, (501) 575-6299, jbalog@comp.uark.edu

ARS scientists have found more than 340 different chemical scents produced by human skin, some of which are attractive to mosquitoes. In laboratory tests, about 90 percent of the mosquitoes come to one particularly alluring mixture. This is impressive, considering a human arm and hand attract about 70 percent of the same species of mosquitoes. The researchers developed a technique using tiny glass beads that adsorb some scents to help identify mosquito-attractive organic compounds from humans. Finding the right chemical scent is important, because what may be attractive for one species may not be for another. Out of 2,700 mosquito species worldwide, four to six dozen transmit diseases, making it difficult to pinpoint attractants unique to each. Ultimately, a better understanding of mosquito attraction should help in developing more effective, environmentally safe repellents for protection from insects that prey on humans and livestock.

Center for Medical, Agricultural, and Veterinary Entomology, Gainesville, FL
Ulrich R. Bernier, (352) 374-5931, ubernier@gainesville.usda.ufl.edu

ARS scientists are closing in on a vaccine that protects fish from a Streptococcus bacterium. ARS is cooperating with scientists of Intervet, Millsboro, DE, to further develop and field test this vaccine under a cooperative research and development agreement. S. iniae is an emerging bacterial pathogen in cultivated tilapia, hybrid striped bass, rainbow trout, yellowtail, eel, and turbot. Worldwide, streptococcal infections are reported in 22 species, both cultured and wild. S. iniae is recognized as one of the most problematic bacterial pathogens in intensively cultured tilapia and hybrid striped bass in the United States. The combination of good health management practices and vaccination is a superior approach to the use of antibiotics or chemicals. Antibiotics are currently used to control the streptococcal disease, which causes $150 million a year in losses worldwide. The Streptococcus bacterium possibly enters the noses of hybrid striped bass and tilapia from the water. The higher the density of cultured fish, the more easily Streptococcus is transmitted and the higher the mortality rate. Signs of the disease in fish are abnormal behavior like erratic swimming, whirling motion at the surface of the water, darkening of the skin, blindness, popeyes, and small lesions on the body, fins, and anus. ARS scientists are also researching fish behavior and health problems related to fungal, algal, bacterial, and chemical toxins implicated in fish kills in U.S. coastal waters.

Aquatic Animal Health Research Laboratory, Auburn, AL
Phillip H. Klesius, (334) 887-3741, klesiph@vetmed.auburn.edu