Medfly's Mealtime Leftovers May Nourish Cattle

Hungry cattle may help solve the problem of what to do with tons of a nutritious mix that's left over from rearing millions of sexually sterile Mediterranean fruit flies.

Agricultural Research Service and University of Hawaii scientists have shown that insectary leftovers make a safe, nourishing and highly digestible feed for livestock. That might help solve the costly environmental problem of how to get rid of this byproduct, generated when insectaries rear the sterile medflies needed to prevent wild, fertile medflies from gaining a foothold in warm-weather states like California and Florida.

Called "spent diet," the caramel-to-brown leftovers look something like moist sawdust or dried oatmeal, and contain water, wheat germ, sugar, yeast and milled wheat bran or milled corn cobs.

Harvey T. Chan, now retired from ARS, and Eric B. Jang of ARS in Hawaii, collaborated in the research with a team led by James R. Carpenter of the University of Hawaii. A medfly factory run by USDA's Animal and Plant Health Inspection Service on the island of Oahu, Hawaii, is currently shipping spent diet to North Shore Cattle Co. on Oahu. Carpenter's group is monitoring the effect of the new rations on livestock weight gains.

The APHIS insectary currently provides about 300 million sterile medflies every week for medfly control in southern California, and generates about 12,000 pounds of the leftover food every day, according to facility director Stuart H. Stein.

The idea of recycling medfly diet isn't new, but the Hawaii studies are apparently the first to provide the data needed for a commercial trial with cattle in that state. For details, see an article from the March issue of ARS' Agricultural Research magazine.

ARS is the chief research agency of the U.S. Department of Agriculture.

Scientific contact: Eric B. Jang, ARS U.S. Pacific Basin Agricultural Research Center, Hilo, Hawaii, phone (808) 959-4300, fax (808) 959-4323, ejang@pbarc.ars.usda.gov.