Johnny Morgan, Blanchard, Tobie M., Gould, Frances I.
LSU AgCenter animal scientist Glen Gentry examines sodium nitrite being used in research to control feral hogs. Gentry said much of the research now is focused on effective ways of encapsulating the chemical, which loses its effectiveness after prolonged contact with air. Photo by Johnny Morgan
The population of feral hogs in the state is continuing to grow, but LSU AgCenter scientists are working to decrease their numbers.
Researchers at the AgCenter Bob R. Jones-Idlewild Research Station are refining a sodium nitrite bait targeted at the invasive species, said AgCenter animal scientist Glen Gentry.
For the past five years, Gentry and others have sought ways to deliver the bait in a humane, yet lethal way. The challenge is that the sodium nitrite loses its potency when exposed to air.
“Sodium nitrite is known to pull moisture from the air once its container is opened,” Gentry said. “Once that happens, the chemical loses its lethal properties.”
While corn seed has been used as the bait, researchers found the pigs actually like pogie fish more, he said. A major problem with using this type of bait is keeping it encapsulated, Gentry said.
“We want to make sure that when the pigs find the bait that none is spilled,” he said.
Gentry said in order to hold the population at current levels, 70 percent of the hog population would have to be eliminated.
Sodium nitrite is effective in taking the oxygen out of the pig’s blood through the formation of methemoglobin. The process causes them to become drowsy, lie down and die, Gentry said.
“All mammals, including humans, have an enzyme that is able to change methemoglobin, which cannot bind oxygen, back to hemoglobin,” Gentry said. “But pigs don’t have as much of this enzyme, so it takes less sodium nitrite to overload their system.”
Gentry is defining the effective lethal dose of sodium nitrite, an effective delivery medium and selective bait delivery system.
Laws and regulations require that the poison must be publicly acceptable and produce a humane death.
“Sodium nitrite is basically a food preservative and is also used as an antidote for cyanide poisoning,” Gentry said. “It takes just 8 grams of sodium nitrite to kill a 100-pound pig,” Gentry said.
During the research period, a number of traps have been used to catch the pigs. But research shows the pigs become educated and won’t come close to the traps if they are not caught when the traps are triggered the first few times.
A 2013 AgCenter survey showed feral hogs are responsible for more than $55 million in damage to agricultural enterprises statewide. Of the crops listed, soybeans took the greatest hit, with famers losing more than $18 million.