Vaccinating laying hens for a respiratory disease need not lower egg production. Mycoplasmosis, a serious respiratory disease of poultry, is caused by a tiny bacterium that can easily be controlled by vaccination. It affects about 80 percent of all laying hens, which must be vaccinated or they will lose 15 eggs per hen each year. Vaccinating laying hens at 18 weeks of age cuts egg losses to only 8 eggs a year compared with nonvaccinated birds. New ARS studies show that the timing of the vaccination is critical. No eggs are lost if the hens are vaccinated at 10 weeks of age—before egg laying begins. This change maintains yearly egg production of about 253 eggs per hen. The corrected timing could amount to a production increase of $82 million a year for the U.S. egg industry. Its annual egg sales are about $3.8 billion.
Poultry Research, Mississippi State, MS
Scott L. Branton (601) 323-2230, sbranton@ag.gov
J. David May, dmay@ag.gov

Studies by ARS and university scientists show for the first time that dogs can be a host of the calf-killing parasite Neospora caninum. The studies also confirm a suspicion that dogs can shed the parasite in their feces. A Neospora-infected dog could transmit Neospora to cattle by defecating on pasture where the cattle graze or on or near the cattle's stored feed or hay. In California, where herd infection rates are particularly high, Neospora is the chief culprit in calf abortions, costing the dairy industry about $35 million annually. Until recently, the only known site of transmission was between the cow's placenta and her fetus. But in a series of experiments, scientists successfully recovered different growth stages of Neospora from dogs. They recovered mature parasites as well as juvenile forms encased in oocysts, spore-like capsules that dogs can pass in their feces. On the farm, producers may want to store feedstuffs in closed containers or fence off feedlots or choice pasture where dogs may defecate. No antibiotics or vaccines are available for treating infected cows. Producers typically cull infected animals, a practice that can be costly. In puppies, severe Neospora infection causes paralysis and death. Mature dogs generally are more tolerant of an infection.
Parasite Biology and Epidemiology Laboratory, Beltsville, MD
Jitender P. Dubey, (301) 504- 8300, jdubey@lpsi.barc.usda.gov
Department of Biology, University of Wyoming, Laramie, WY
Milton McAllister, (307) 742-6638, milt@uwyo.edu

Turkey breeders will be able to single out potential sires with a technique that examines how well sperm swim. The test objectively measures what's called sperm mobility—how well sperm from each male can swim into a solution at body temperature. The test mimics the environment the sperm encounter in the hen's reproductive tract. ARS scientists in collaboration with Oregon State University scientists modified the test for turkeys. Essentially 100 percent of all turkeys produced annually in the United States are conceived via artificial insemination. With advances in genetic selection, adult turkey toms can weigh up to 85 pounds. A hen, however, weighs only around 20 pounds when she begins to lay eggs. This size difference and the efficiency of artificial insemination have resulted in breeders relying solely on artificial insemination for reproduction of their turkey flocks. Sperm are generally pooled from up to 10 to 15 males. It had been assumed that all of these males would produce similar number of offspring. However, ARS scientists in collaboration with scientists at Tuskegee University in Alabama found that a majority of offspring were produced by few males. So it's critical to determine why paternity efficiency differs so greatly between individuals. In the past, most semen evaluation tests have not predicted fertility potential of sires. The Sperm Mobility Test is predictable. By sorting out infertile toms, turkey breeders could potentially save millions of dollars annually.
Germplasm and Gamete Physiology Laboratory, Beltsville, MD
Ann M. Donoghue, (301) 504-8580, annie@ggpl.arsusda.gov

Beef cattle herd replacements may be raised less expensively without affecting their performance as cows. The key: Reduce their feed and defer some of their weight gain until grass is available during breeding season. In a study that included 1,275 crossbred heifers from seven breeds of sires, the most heavily fed heifers gained about a 1.5 pounds per day between weaning and breeding while those fed 20 percent less gained about 1 pound. Differences between the two groups' rate of gain reversed during the breeding season, when heifers were allowed free access to grass. Heifers that had been fed the moderate level gained 0.4 pound per day more than heifers that had been on the high level of feed. Depending on sire breeds, heifers differed in their age at puberty, age at calving, milk production and weaning weight of their calves. Prebreeding feed level had no influence on these traits.
U.S. Meat Animal Research Center, Clay Center, NE
Harvey C. Freetly, (402) 762-4202, freetly@email.marc.usda.gov