Using Soldier Files as a Manure Management Tool for Volume Reduction, House Fly Control and Feedstuff Production (LS93-056)
Manure is the principal food of many insects, especially larval flies. The insect utilization aids in the natural recycling of manure and the insects produced are food for many larger animals. Several researchers have proposed using manure as a larval fly medium, thus producing high quality insect-based feedstuff, while reducing manure residues. These systems all required separate facilities and sophisticated separation equipment. The results were good, but too expensive to be practical. The system we report here utilizes wild populations of the black soldier fly, Hermetica illucens (L.), directly under caged layers. No separate facility or special equipment is needed for production or harvest. This is possible due to certain habits of this large wasp-like fly, i.e. it is not a significant pest (especially as managed in our system) and the migrations of the last immature stage facilitate a simple self-collection of the mature larvae (prepupae).
Soldier fly larvae have been fed experimentally to several animals, with larvae used to replace soybean or fish meal in a formulated diet. These feeding tests have involved chickens, swine and fish, and response has been good. The dried prepupae, as collected in this system, contain 42% protein and 35% fat. Fat and protein meal fractions were easily separated by a commercial rendering plant. Amino acid and fatty acid profiles of these fractions are favorable. Bull frogs were raised for two years (two trials) on this unique, live feedstuff and may be the best way to capture maximum value from this system.
The black soldier fly is an attractive manure management agent since it can (1) eliminate house fly breeding: (2) reduce manure bulk by half or more when compared to similar unoccupied manure; and (3) produce economically attractive quantities of larval based feedstuff. An earlier study with this soldier fly driven manure management system produced almost 1.2 lb of larvae per hen annually, from May to December. This would be 58 tons in a 100,000 hen high rise caged layer house.
The currently reported study tested this system in a 1900 hen, small scale high-rise layer house to determine feasability of transfering this technology to a full sized house. Configurations of collection systems were tested, as were manure clean-out dates to best manage the soldier flies and not have house fly outbreaks. Changes in plant nutrients in the manure caused by soldier fly larvae were determined. Colonizing of soldier flies was investigated and bull frog culture using the self-collected prepupae was tested.
The following conclusions were drawn from these studies:
1.) Establishment of a self sustaining soldier fly population was easily accomplished with one relatively small innoculation of larvae.
2.) Self-collection ramps 29″ tall with a 35° slope performed very well. Steeper ramps were difficult for prepupae to climb. Overall the self-collection system worked very well in our small caged layer facility. Efficient collections would be possible with a ramp on each side of a full sized caged layer house.
3.) Almost complete house fly suppression was achieved with the naturally regenerating soldier fly population.
4.) House fly outbreaks occurred following hens installed in September and a manure clean out in August. These events presented house flies with abundant, SFL-free manure, and were the only times outbreaks occurred.
5.) Manure clean-out in February or March were desirable both for timely utilization on crops and for house fly suppression.
6.) Nitrogen content in manure residue from SFL is significantly less and phosphorous is not higher.
7.) Winter accumulation of very dry manure led to two problems not seen previously:
a. Prepupal soldier flies pupated in dry manure base and were not self-harvested.
b. A lesser mealworm outbreak occurred in the dry manure.
8.) Conclusion 7b points out that lesser mealworms do not survive in a typical robust SFL population. A recent national workshop on livestock and poultry pests identified the lesser mealworm as a key pest of broiler production. If broiler manure could be managed with soldier flies, then the broiler industry would have a biological control for lesser mealworms, as well as the benefits expected for caged layers.
9.) Preliminary attempts indicate that colonization of BSF is feasible. Management of wild BSF populations has proven very successful for our manure management system, but colonization of this insect would increase confidence in the system with those considering its adoption.
10.) Bull frogs were successfully cultured with an adult diet of live BSF prepupae offered with catfish fingerling diet. Our frog culture was loosely based on a successful commercial system from Latin America which uses expensive live house fly larvae.
Adoption of this system in confined animal feeding operations seems feasible. Economic returns could be significant and manure to be land-applied would be reduced over 50%. Access to the manure in modern high-rise caged layer houses by wild ovipositing females is problematic, but several solutions are possible. This system can readily be adopted to animal production more open to the environment.