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Scientists Seek New Clues on Salmonella

By Jill Lee
April 9, 1998

Molting--a period when hens get a break from egg-laying--is known to raise the birds' overall egg production. Now, scientists are testing some promising new ideas for preserving hens' health as well as food quality before and after the two-week molt period.

Egg production drops when hens reach 60 to 65 weeks of age. Many U.S. farmers solve this problem through feed restriction. Restricting feed temporarily shuts down the egg-producing part of the bird's system. That's because when feed is in short supply, the bird's body halts processes that are not vital for survival--and egg production is usually the first to go. This process, called molting, allows the hen's reproductive system to rest briefly, which ultimately restores 85 percent of the bird's original egg production level.

But undetected infections of Salmonella enteritidis can grow rapidly during this time. That increases the risk that the hen's post-molt chicks or table eggs will also be infected. Many farmers won't take chances. Evidence of salmonella infection prior to molt means slaughter--and money lost.

The farmer's European counterparts are less likely to molt their birds, but they do have treatments for enteritidis. Their veterinarian can prescribe Enrofloxacin. The treatment is re- enforced by another product, Avigard, that helps prevent Salmonella enteritidis from coming back after the Enrofloxacin treatment is completed. U.S. veterinarians can prescribe Enrofloxacin to protect poultry--and Avigard to protect the eggs--but only from E. coli.

Microbiologist Peter Holt with the Agricultural Research Service is testing the effectiveness and safety of Enrofloxacin and Avigard under a cooperative research agreement with Bayer Corporation. As with any new pharmaceutical, an intriguing success overseas is promising, but lacks the evidence needed to make it available for U.S. producers.

But Holt is also researching low-tech, natural alternatives. He found that putting hens on a low-calcium reduced-calorie diet instead of restricted feeding reduces Salmonella enteritidis levels up to 100 fold. Holt is conducting more in-depth studies of the low-calcium strategy at ARS' Southeast Poultry Research Laboratory in Athens, Ga.

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