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The Food Insects Newsletter

Large-scale Feed Production from Animal Manures
with a Non-Pest Native Fly

July 1992. Volume 5, Issue #2.
By D. C. Sheppard, Ph.D.
University of Georgia
Coastal Plain Experiment Station
Tifton, GA 31793

The black soldier fly, Hermetia illucens (L.), is an attractive manure management agent that can produce large quantities of high-quality animal feedstuff, control house flies and reduce manure residue by half. Based on a 480 hen pilot scale test (Sheppard et al 1992) a modest-sized 20,000 hen caged layer facility could collect over 13 tons of larvae from June through December. Sixty thousand hens per house is now the preferred size and farms usually have multiple houses. This 13 ton production estimate from a small commercial unit is probably low. Future systems will be managed better than this first trial. Early season collections were not measured, and a late summer manure clean-out lowered production. Deeper manure basins in future systems should allow utilization of manure collected during the winter.

Prepupal soldier flies were self-collected as they sought pupation sites and crawled out of the manure basin. A 40° slope on one wall of the basin directed these mature larvae. They crawled into a U2 inch slit in a 6-inch diameter PVC pipe at the top of this slope. Then they continued to crawl to a container at the end of the pipe. In the experimental facility they easily negotiated a 40-foot length of pipe. The masses of exiting prepupae sometimes clogged a 4-inch pipe, which was used at first, but the 6-inch pipe worked well. The opposing 12-inch wall was vertical and kept the masses of larvae off of the house's central walkway. If not contained, these masses of larvae can cause aesthetic problems.

Newton et al (1977) found that manually collected soldier fly larvae contained 42% crude protein and 35% fat. Self-collected prepupae should be of higher feed value since they average larger, have emptied their gut and have more stored fat. Tests are underway to determine the feed value of the self-collected prepupae. Manually collected larvae have been studied, and show promise as a feed ingredient for swine (Newton et al 1977), poultry (Hale 1973) and fish (Bondari and Sheppard 1981). Swine relish the fresh larvae.

Little is known about adult biology. The only adults commonly seen are newly emerged adults and ovipositing females. Eggs are laid in batches of about 500 in dry cracks or crevices above the chosen larval media Other adults apparently live in a wild environment and their habits are largely unknown. They do not try to enter houses and are usually not a problem. In 15 years of investigating this insect, I can remember only one complaint about adults entering a residence.

Besides offering a potential feed source, soldier fly larvae provide two other significant benefits: house fly control and about a 50% reduction in manure volume (Sheppard 1983). The larvae repel ovipositing female house flies (Bradley and Sheppard 1984) and house fly larvae that do attempt to compete with dense populations of soldier fly larvae usually die. In the pilot scale manure management test mentioned earlier no house fly breeding occurred from June to December. Many Georgia egg producers use this insect for house fly control without any management to contain the soldier fly larvae.

The economics of this manure management system are attractive. Construction costs should be less than the currently popular flush systems and resource recovery is greater.

The only insecticide able to approach the level of control achievable with this system is Larvadex, when house flies are susceptible. With low levels of Larvadex resistance, soldier fly larvae provide house fly control superior to Larvadex (Sheppard et al 1989). Larvadex costs an egg producer 10 cents per hen if used for 6 months. Thus a conservative value to place on house fly control with this soldier fly system is 10 cents per hen per year. Manure removal and surface application costs 65 cents per hen, per year in shallow pit houses (Ritter 1992). Assuming 50% reduction in manure build-up through soldier fly activity (Sheppard 1983) for half the year gives a 25% reduction on an annual basis. Actual reduction may be much more if manure basins deeper than 12 inches are used, and soldier fly larvae can digest manure from the previous winter. At any rate, the conservative 25% reduction estimate produces an economic benefit of 0.25 x 65 cents = 16.2 cents per hen per year. This assumes the manure is a liability, which it generally is in high production areas. Value of the dried larval feedstuff has been estimated at $340-400 per ton. At 44% dry matter, the fresh larvae are worth about $160 per ton or 8 cents per pound. So, the 1.32 pounds of larvae produced per hen per year are worth 10.6 cents. Adding the easily measured economic benefits of this system yields a total value of 36.8 cents per hen per year. This would net our small hypothetical 20,000 hen egg producer an extra $7,360. This system should easily adapt to swine waste management, and a trial is currently underway. Soldier flies could be used to degrade many other organic wastes. They have even been found breeding in ketchup and formalin preserved tuna (May 1961), and can eliminate house fly breeding in privies (Kilpatrick and Schoof 1959).

References cited:
Bondari, K., and D.C. Sheppard. 1981. Soldier fly larvae as feed in commercial fish production. Aquaculture 24: 103.
Bradley Susan W., and D.C. Sheppard. 1984. House fly oviposition inhibition by larvae of Hermetia illucens, the black soldier fly. J. Chem. Ecol. 10:853-859.
Hale, O.M. 1973. Dried Hermetia illucens larvae (Diptera: Stratiomyidae) as a feed additive for poultry. J. Ga. Entomol. Soc. 8:16-20.
Kilpatrick, J.W., and H F. Schoof. 1959. Interrelationship of water and Hermetiaillucens breeding to Muscadomeshca production in human excrement. Am. J. Trop. Med. Hyg. 8: 597-602.
May, B.M. 1961. The occurrence in New Zealand and the life history of the soldier fly Hermetia illucens (L.)(Diptera: Stratiomyidae). N.Z.J. Sci. 4:55-65.
Newton, GL., C.V. Booram, R.W. Barker, and O.M. Hale. 1977. Dried Hermetia illucens larvae meal as a supplement for swine. J. Anim. Sci. 4:395-399.
Ritter, W.F. 1992. Selecting poultry waste systems increasingly important. Feedstuff 63: 30-32,41-42.
Sheppard, C. 1983. House fly and lesser house fly control utilizing the black soldier fly in manure management systems for caged laying hens. Environ. Entomol. 12: 1439-1442.
Sheppard, D.C., N.C. Hinkle, J.S. Hunter III, and D.M. Gaydon. 1989. Resistance in constant exposure livestock insect control systems: a partial review with some original findings on eyromazine resistance in house flies. Fla. Entomol. 72: 36~369.
Sheppard, C., L. Newton and S. Thompson. 1992. Manure management for house fly control, volume reduction and feed production, using the black soldier fly. Proc. of the Nat. Organic Farming Sym., Pacific Grove, California Jan 22-23, 1992.

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