黑水虻

黑水虻 Black Soldier Fly and Others for Value-Added Manure Management Craig Sheppard University of Georgia Tifton, GA 31794 ABSTRACT Many scientists have known insects can digest manure and produce high quality feed for animals. Most of these have studied the house fly because the biology is well known, it is prolific and it produces a high protein feed. These systems have not been widely utilized because of the relatively highcost of managing the house fly. Biosecurity, the need for a separate facility and labor forharvesting increase the cost of production. The black soldier fly’s habits and non-pest statusallows for development of low-cost production. Black soldier fly larvae consume a wide variety of organic matter including animal manures and food waste. While consuming this material they assimilate nutrients thus significantly reduce its volume and ——————————————————————————————————————————————— pollution potential. They also control house flies through competition, and produce high quality feedstuff and other products. The biology and habits of this large wasp-like fly make it well suited to large scale value-added waste management. Adults live and matenear larval habitat, not seeking to enter dwellings as house flies do. Adults do not need to feed,surviving on the large fat body developed as a larvae. This beneficial insect occurs worldwide intropical and warm-temperate regions. Larvae occur in very dense populations, often covering thelarval food resource in a solid layer. Mature larvae migrate from this mass of feeding larvae to find protected pupation sites. The migration of this energy and protein rich prepupae makes self-harvest possible. Prepupae do not feed and have an empty gut, making this the ideal stage tocollect for a feedstuff. A very simple system has been developed for manure management in animal housing where wild populations of black soldier fly colonize the fresh manure that has dropped to a lower level. A simple ramp and PVC pipesystem directs prepupae to self-harvest for resource recovery. No extra facility or energy arerequired. This system can work for a few animals or a large farm. Projections indicate ——————————————————————————————————————————————— that 58tons of prepupae could be self-collected from the manure of 100,000 hens in 5 months. One feeder pig (annual space) averaging 70 kg would produce 63 kg of prepupae worth over 12 USD. These larvae are 44% dry matter, and the dried feedstuff is 42% protein and 35% fat. Manure tolarval conversion on a dry matter basis has been up to 8% for hens and 15% or more for swine. Published feeding studies have shown the dried larval feedstuff to be a good replacement forsoybean or meat and bone meal in the diets of swine, poultry and fish. Bull frogs have beenreared in two trials on a live soldier fly larvae with a pelleted feed mixture. Other utilization ofthis unique larval product may involve oleic-and linoleic essential fatty acids, which make upover 20% of the fats in the prepupae, and chitin with its many medical and industrial applications. Recent feeding studies show that the prepuape can effectively replace high qualitymenhaden fish meal with a value of 500 USD/ton. Current research is being conducted on adult biology, colonization to support large scaleuse of this system in modern animal housing and nutrient depletion from the larval digested manure. This nutrient depletion from manure would aid pollution abatement in areas of confinedanimal feeding operations. Insect Digestion of Manure ——————————————————————————————————————————————— Insects, especially various fly larvae (maggots) and beetles readily feed on fresh manure,converting residual protein and other nutrients into biomass, which is a high quality animalfeedstuff. Considerable research has been conducted to understand and exploit this activity formanure management. Scientists in Vietnam, Thailand, China, USSR, USA, Mexico, EasternEurope, Israel, Australia and Central and South America have studied manure digestion withinsects to produce high quality feedstuff. Lately, the emphasis has shifted from feedstuff production to using insects to solve the problems associated with the large amounts of manureproduced at confined animal feeding operations (CAFO’s). While incorporating and concentrating nutrients from manure into more valuable biomass (animal feedstuff), insect larvaereduce the nutrient concentration and bulk of the manure residue, thus reducing pollutionpotential 50-60% or more. Because of its much higher value ($500/ton), this feedstuff can beeconomically hauled significant distances to relieve local nutrient overloads. Also, whileoccupying the manure the insects aerate and dry it, reducing odors. Maggots modify themicroflora of manure, potentially reducing harmful bacteria. The high-value insect feedstuff,reduction of the manure mass, moisture content, offensive odor and pollution potential are therewards for good management of such a system. ——————————————————————————————————————————————— All published work known to the author on insect digestion of manure relates to maggotproduction. High reproductive and growth rates make flies (maggots are the larval growth stage)the best candidates. Flies that have been used experimentally to process manure include houseof these are considered pests as adults due to their disease vector potential, behavior and preferred habitats. Most current research is being done with the house fly and black soldier fly,so the following discussion will be primarily limited to these. Papp (1974) reported an 8% conversion of pig manure to house fly larvae (dry matter,d.m. basis). Chiou and Chen (1982) found that blow flies converted 50 to 60% (depending onfeeding rate) of swine fecal mass to larval mass, including recovery of up to 55% of the manureorganic carbon as larval carbon. Black soldier fly larvae converted manure in a 460 hen facilityto self-collected prepupal biomass at a 7.8% (d.m. basis) rate (Sheppard et al. 1994), whichwould represent 58 tons from 100,000 hens in 5 months. House flies under optimum laboratoryconditions converted poultry manure to pupae at a 7.6% rate (Miller et al. 1974). In a recentstudy with swine, the authors observed 15% d.m. conversion of manure to black soldier flyprepupae. Research by Engineering, Separation and Recycling (L.L.C.) of Washington, LAfound a 24% d.m. conversion of food waste to soldier fly prepupal biomass. The mouth ——————————————————————————————————————————————— parts ofsoldier fly and blow fly larvae allow them to macerate solids, apparently resulting in utilizationof greater proportions of solid resources than is possible with house fly culture. Manure-fedmaggots convert feed to weight gain with at least the efficiency of our most efficient concentratefed domestic animals. In all successful published trials fresh, aerobic manure was used. Beard and Sands (1973)and Morgan and Eby (1975) reported that anaerobic manure was lethal or at best “unsuitable” forfly larvae development. Even aerobic manure a few days old supported significantly less survival and growth of house fly larvae. This reduced performance may be due to depletion ofnutrients by microorganisms or development of conditions directly detrimental to larval development. Beard and Sands (1973) wrote that established house fly larvae slowed bacterialgrowth. Black soldier fly larvae also require fresh manure. Old or stockpiled manure has supported poor larval growth. Because of the need for very fresh manure, insect digestion is bestdone as a continuous process directly under the poultry or livestock, a practical system with blacksoldier fly. This allows for immediate consumption before any competitive bacterial action andsaves the expense of handling. The manure is reduced in-place and less hauling is required. Serial batches started at short ——————————————————————————————————————————————— intervals have been successful with house flies (Morgan and Eby1975, Eby and Denby 1978), but require much more labor and a separate facility. The blacksoldier fly is well suited to continuous digestion directly under the animals (Sheppard et al.1994). Twenty or thirty years ago in the southern United States dense soldier fly populationswere common in open poultry and swine housing where the animals were held on wire or slats. Here soldier fly larvae were present by the millions in a layer covering the manure bed underthese animals. Fresh manure was consumed immediately. Adults were hard to find since onlythe ovipositing females returned to the facility. These situations were common in the southeastern US and west to California (Furman et al. 1959). These unmanaged populationseliminated house fly breeding and reduced manure residue (Sheppard et al. 1983) but feedstuffharvest was never attempted. A simple ramp and pipe system has been developed (Sheppard etal. 1994) which directs migrating prepupae to collection containers. Modern, environmentallycontrolled animal housing makes the manure inaccessible to soldier fly adults, even though houseflies often flourish there. Recently developed rearing techniques for black soldier flies (Sheppardet al. 2002) allow for introduction of soldier fly larvae to digest manure in these modernfacilities. Wild females can dependably innoculate manure in open sided housing. ——————————————————————————————————————————————— Bacteriological interactions associated with manure digestion by maggots are favorable. Maggots are competitors with bacteria for nutrients and often reduce bacterial numbers greatly, or eliminated them altogether (Beard and Sands, 1973; Sherman, 2000). Maggots may consumeand digest microorganisms, and produce antibacterial and/or fungicidal compounds (Landi, 1960;Hoffmann and Hetru, 1992; Levashina et al., 1995 and Landon et al., 1997). As maggots reducepathogens in manure they may make it safer for organic vegetable production. Foodborne illnessassociated with fresh produce has doubled in the last 20 years in the US and is associated withlikely among people who consume organic foods than those who do not. Preliminary studieswith black soldier fly larvae indicated a reduction of pathogens in an artificial medium or manure innoculated with larvae. Numerous studies using dried, rendered and fresh maggots as animalfeed have revealed no health problems resulting from this practice. Preliminary bacterial culturing of self-collected soldier fly prepupae from a recent swine trial revealed no pathogens. House flies have been the agent of choice in most studies because of their high reproductive rate, short life cycle (2 weeks at 25?C), well understood biology, and the ability toflourish in virtually any animal manure. El ——————————————————————————————————————————————— Boushy (1991) reviewed the use of house flies toconvert manure to high quality animal feed. With any fly species to be used as feed, maturelarvae or pupae are the preferable stage for harvest. Losses of biomass by migrating larvae andin pupal development cause the adult to be about half the weight of the mature larvae (Papp1974) and the more chitinous exoskeleton of the adult may reduce nutrient availability. Feeding studies with house fly and blow fly based feedstuffs have shown them to be generally equal to soybean meal (and other conventional ingredients) in feed value when fed tochicks, rats, pigs, or trout (Calvert et al, 1969; Dashefsky et al., 1976; Finke et al., 1989; Gawaadand Brune, 1979; Too et al., 1980; Teotia and Miller, 1974; Poluektova et al., 1980; Khan et al.,1999). Soldier fly prepupae have been fed experimentally to several animals, replacing soybeanor fish meal, along with added fat, in formulated diets. The prepupae used in these trials contained 41-42% crude protein, 31-35% ether extract, 14-15% ash, 4.8-5.1% calcium, and 0.60-0.63% phosphorus, on a dry basis. These feeding tests utilized chicks (Hale 1973), pigs (Newtonet al., 1977), catfish and tilapia (Bondari and Sheppard, 1981, 1987), or frogs (Newton and Sheppard, unpublished data). The general conclusion of each of ——————————————————————————————————————————————— these studies was that soldier flylarvae or larval meal was a suitable replacement for a high proportion of conventional proteinand fat sources. A recent replicated catfish fingerling feeding study demonstrated that BSFprepuape can replace high quality fishmeal with essentially the same growth, in spite of lossesapparent with the fresh chopped prepupae. Fish on both diets tripled weight in 55 d. Themenhaden fishmeal fed as the standard in this study is valued at about $500 per ton on thecommodity market (Feb., 2002). Separation of the protein and fat in soldier fly prepupae byrendering is feasible and will allow for more precise diet formulation. Simple drying and millingthe prepupae allows for easy incorporation into modern animal diets. Experimental rendering ofsoldier fly prepupae produced a meal with 62% crude protein and an oil which was high indesirable medium chain and monounsaturated fatty acids (Sheppard and Newton, 1999). Insect digestion of manure as a primary treatment is promising. This process reducesmanure mass, nutrient content, moisture and odor, while producing high quality feed. Moststudies have been conducted with the house fly because it is easily reared and well known. Highenergy and equipment costs probably explain why house fly systems have not been adopted. Better understanding of the biology and culture techniques for the black soldier fly are supportingdevelopment of a very low cost system to exploit the advantage of insect digestion of manure. ——————————————————————————————————————————————— Factors relating to the use of these two insects are given in Table 1. There is still considerable interest in using house flies for manure digestion, notably in Israel and Chile. A better understanding of how to utilize the black soldier fly is generating interest in the US, Vietnam,and Israel. Engineering, Separation and Recycling (L.L.C.) from Washington, Louisiana hasdeveloped and patented innovative manure handling equipment to compliment soldier fly manuredigestion by removing the oldest manure from the bottom of the basin. This facilitates thecontinuous process. Current research needs include developing practical commercial scale systems, determining optimum utilization of the high value feedstuffs, determining bacterial interactions,including safety of feedstuffs and developing more efficient culture techniques for the blacksoldier fly. Nutrient depletion of manure residue following maggot digestion has been variable. Studies on maggot culture and environmental conditions are needed to maximize nutrientreduction, especially phosphorous. Table 1. A comparison of some factors relating to house flies and black soldier flies as manure management agents. Life Cycle at 27?COccurs WorldwidePupal WeightPupal: Protein Fat ——————————————————————————————————————————————— Dry Matter Manure to Feedstuff Conversion(d.m. basis)Pest Status 13 daysYes 0.013-0.026gm63%9-15%30% 4.2 to 8.0% in swine manure; 10%maximum theoretical(Papp 1974) Severe - Vectors numerous diseases; Containment necessary;Associated with 277 diseaseorganisms; Adults domesticSeparate facility necessary forrearing and mechanical separationSolid to semi-solid substrateAll published systems requiremoving fresh manure requiringmore labor Equipment and energy input required for separation by floatationor screening Required for successfulreproduction 30-50% compared to fresh manure(Miller et al. 1974)20% (independent of massreduction)Yes Easily cultured in small cages. Biology understood in great detail. Must be cultured and containedbecause of pest status 38 daysYes0.10-0.24gm42%35%43-44% 15-20% seen in practical swineapplication; 24% with food wasteRoutinely not a pest; No knowndisease transmission exceptaccidental enteric myiasis;Containment optional; adultsoccupy wild environment ——————————————————————————————————————————————— Current systems rear larvae in lowerlevel of animal housing where self-collection also occursSolid to semi-solid substrateFresh manure digested in-place;Reduced residue removedperiodically Migratory habits of prepupaeallows self-collection with noenergy input and no separatefacility Not required for successfulreproduction 42-56% compared to same agemanure which was also reduced(Sheppard 1983) 25%+ (independent of massreduction)Yes Requires “walk-in” cage to allowadult mating; Continuous culturemaintained for 2 years, but biologyincomplete; Can exploit wild,managed populations and omitcaptive culture of this virtual non-pest Facility Needs Preferred Larval HabitatManure Handling Insect Harvest for Feedstuff Feeding of Adult FliesManure Mass Reduction Nitrogen Reduction in ResidueReported Odor ReductionCulture Technique Literature Cited Beard, R.L. and D.S. 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