Tons of a nutritious mix that's left over from rearing sexually sterile Mediterranean fruit flies make a safe, nourishing, and highly digestible feed for livestock. ARS and University of Hawaii scientists have shown that this recycling of the leftover material, called "spent diet," could help solve the costly problem of its disposal. Spent diet is generated when insectaries rear millions of medflies. The insects are sterilized, then used to prevent wild, fertile medflies from gaining a foothold in warm-weather states like California and Florida. When sterile males mate with their wild female counterparts, no viable offspring result, so the population crashes. The caramel-to-brown spent diet looks something like moist sawdust or dried oatmeal and contains water, wheat germ, sugar, yeast, and milled wheat bran or milled corncobs. A medfly factory run by USDA's Animal and Plant Health Inspection Service in Hawaii is currently shipping spent diet to North Shore Cattle Co., Haleiwa, HI. The insectary 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. Some foreign insectaries already recycle their leftovers as feed, but the ARS and University of Hawaii study is the first to provide data needed for the commercial trial with cattle in Hawaii. University researchers are monitoring the effect of the new rations on livestock weight gains.

U.S. Pacific Basin Agricultural Research Center, Hilo, HI
Eric B. Jang, (808) 959–4300, ejang@pbarc.ars.usda.gov