Medfly Leftovers=Gourmet Feed
ARS entomologist Eric Jang
(left) and Stuart Stein, director
of the USDA-APHIS Hawaii Fruit
Fly Rearing Facility, examine a
spent larval diet before shipping
it to livestock yards where
it will be fed to cattle.
Nutrients left over from
mass-rearing of Mediterranean fruit flies make a good feed for livestock,
according to ARSand university
researchers in Hawaii. Their investigations could help convert a costly
environmental problem into a new supplement for cattle or other animals.
To fight outbreaks of the Mediterranean fruit fly, or medfly, states like
California and Florida rely on shipments of millions of sexually sterile
medflies reared in laboratories. A medfly factory run by USDA's Animal and
Plant Health Inspection Service (APHIS) in Waimanalo, Hawaii, for example,
supplies some 300 million sterile medflies every week for medfly control in the
Los Angeles basin. When these sterile males mate with wild medfly females, no
viable offspring resultand the population dies out.
For part of the time when the medflies are growing at the mass-rearing
facility, they eat a nutritious mixture of water, milled wheat bran or milled
corn cobs, wheat germ, sugar, and yeast. The diet is caramel-to-brown in color
and looks something like moist sawdust or dried oatmeal.
Stuart Stein (left) and Eric Jang inspect
a larval diet for medflies.
Once the mix is no longer needed
to nourish the insects, APHIS pays about $100,000 a year to dispose of the used
or "spent" medfly diet. The Waimanalo plant generates about 12,000
pounds of this material every day. Getting rid of it is an environmental and
economic problem, according to Waimanalo director Stuart H. Stein.
Now, ARS scientists and their University of Hawaii colleagues have shown
that spent diet can be used as livestock feed. The researchers determined the
amount of protein, fat, carbohydrate, minerals, and other nutrients in spent
diet from the APHIS facility and two other rearing labs in the state. Their
tests with cattle and sheep showed that it is safe to eat and highly
digestible. Harvey T. Chan, now retired from ARS, and Eric B. Jang of the ARS
U.S. Pacific Basin Agricultural Research Center in Hilo, collaborated in the
research with James R. Carpenter, Ruth Y. Niino-DuPonte, Harry M. Ako, and
Halina A. Zaleski of the University of Hawaii College of Tropical Agriculture
and Human Resources.
Medfly larvae consuming a highly
nutritious corn-based diet.
The idea of recycling medfly diet
isn't new. University scientists, for example, fed it to pigs for a study in
the 1980s. In addition, some foreign labs that rear medflies already recycle
their leftovers as feed. But the new studies are apparently the first to
provide the data needed for a commercial trial with cattle in Hawaii.
The North Shore Cattle Company on the island of Oahu now has an agreement
with the Waimanalo factory to receive all of the used diet that it can provide,
according to Stein. University scientists will monitor the effect of the new
rations on the cattle weight gains that are essential for a profitable herd.
Spent diet has the potential to replace 10 to 15 percent of the feed that
Hawaii's livestock producers buy from other states as a supplement for their
animals.By Marcia Wood,
Agricultural Research Service Information Staff.
This research is part of Crop Protection and Quarantine, an ARS National
Program (#304) described on the World Wide Web at
Eric B. Jang is with the
USDA-ARS U.S. Pacific Basin
Agricultural Research Center, Stainback Hwy., P.O. Box 4459, Hilo, HI
96720; phone (808) 959-4300, fax (808) 959-4323.
"Medfly Leftovers=Gourmet Feed" was
published in the March 2000 issue
of Agricultural Research magazine.