‘Grubby’ research promises manure benefits

STEPHENVILLE, Texas – Jeff Tomberlin’s research could lend a whole new meaning to the phrase “grub for a living.”
Tomberlin, a Texas A&M entomologist, is looking into the possibility that black soldier fly larvae – “grubs” to the uninitiated – could be used to turn livestock manure into high-protein feed.
The concept. The concept itself has been proven practical for reducing poultry litter: The flies lay their eggs in the animal manure without much encouragement.
The eggs hatch into larvae that eat the manure as if it’s caviar, growing into fat little creatures that are 40 percent or more protein.
The chickens do what chickens do naturally, eat the worm-like larvae with relish, Tomberlin said.
“No special harvest equipment is needed,” he said.
Adaptation. Tomberlin expects to find the same manure-reduction techniques that work with poultry can be adapted to other livestock operations, including feedyards.
Whether the larvae can be recycled as livestock feed is another question, but he has plans to investigate this as well with feeding trials.
Tomberlin does know that when large numbers of soldier fly eggs are introduced to a manure pile, the resulting larvae can reduce dry weight of the manure by 30 percent to 50 percent in two weeks.
Preliminary work with calf hutches shows this to be true.
Phosphorous. “We also showed the residual manure nitrogen and phosphorus was reduced by half. Reducing phosphorus levels are particularly important, as excess phosphorus can be a primary pollutant,” he said.
“We’re just learning to use what Mother Nature has already provided to reduce pollution.”
House flies. The soldier fly does not invade houses or become a pest to domestic animals.
“The adults are short-lived and prefer to live in a wild environment,” he said.
Even better, Tomberlin said, introducing black solder flies to manure can actually reduce the numbers of house flies because the two species compete for larval habitat. Female house flies will not lay eggs where soldier fly larvae are abundant.