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Protein from Thin Air:

Breeding Fly Maggots for Poultry Feed

A Crucially Important Advisory to the Reader

Please be advised that, despite what is said below about the chances for disease with this system, and despite the fact that I have used it successfully for years, I have recently indeed had problems—including deaths of several chickens—that probably resulted from “limberneck”—that is, botulism poisoning.

On one occasion, I cycled through the maggot buckets offal from chickens (from a buddy who came over to share my equipment) that had not been properly starved—their crops were filled with feed, which may have soured and supported the growth of Clostridium botulinum (the microbe that produces botulinum toxin). In another, I put a couple of groundhogs into the buckets that had been sitting around perhaps too long—maybe the C. botulinum had had longer to get a start, than it would have if I were using fresher carcasses.

In any case, I have a duty to warn the reader about these problems I have had, and advise that I'm more cautious about use of this method of generating “free protein” than when I wrote this article. I have not given up on the maggot buckets—I may well experiment further to determine how to reap the benefits of the system, without creating a danger to my flock—but for the moment I have suspended use of the maggot buckets. Fresh carcasses that come my way I am feeding to the layer flock directly, not as maggot-generating substrate. My past experience indicates that the chickens resist eating a carcass encased in fur. However, if I open it up a bit with a hatchet, they utilize the muscle tissue and internal organs quite efficiently.

If there is an inherent problem with the maggot buckets, it has much to do with the anaerobic nature of the feeding medium—anaerobic conditions are more conducive to pathogens (including C. botulinum) than aerobic ones. That's why I am excited about use of Black Soldier Fly larvae for responsibly recycling various organic residues, recapturing their residual nutrient content for soil fertility applications, and even (as with blowfly maggots) generating high quality live animal feed for the flock (42% protein, 35% fat on a dry-weight basis). I am now experimenting with a “BioPod” for working with this species. The feeding activity of BSF larvae is a much more aerobic process, with a greatly reduced chance there could ever be a disease complication.

My next article in Backyard Poultry Magazine will be an introduction to Black Soldier Fly; and eventually I will post more information on the site. In the meantime, please check Black Soldier Fly Blog and The BioPod for more information. Stay tuned!

~Harvey, August 1, 2009

This article was published as a sidebar to “Feeding the Flock from the Homestead's Own Resources” in the Oct/Nov 2006 issue of Backyard Poultry Magazine.

Using food grade 5 and 7 gallon buckets, I drilled numerous 3/8-inch holes in the bottoms, sides, and screw-on lids. (Holes of this size allow flies to enter, but prevent pecking by the chickens.) My buddy Sam keeps me supplied with 30-35 lb beaver carcasses. These I seal inside the buckets. After just a few hours, flies have “blown” the carcasses with eggs, which within a day hatch into a mass of greedily feeding larvae, or maggots.


Suspend the Buckets

Please note that for this system to work, it is essential that the buckets be suspended, either by hanging (from a tree or a rafter of a shelter) or by placing on a wire platform. When the larva has grown enough to pupate, it has the instinct to leave the feeding medium and burrow into the ground—it will not pupate in the feeding medium. By suspending the buckets, I ensure that larvae migrating out of the carrion will free-fall, attracting the attention of the ever-alert chickens, who instantly snap them up.

I have found the beaver carcasses from my friend to be tremendously productive. He also passes on the occasional raccoon, and I have even cycled the odd roadkill through my buckets, as well as a groundhog who sadly did not understand the intensity of my feelings about my sweet potato planting. When I slaughter poultry for the table, I now run the offal through the buckets as well—a more efficient, and productive, way of disposing of them than burying or composting. I even put in any domestic birds that died by accident, though of course do not use carcasses of birds who may have died of disease.


Divide the Carcass

No doubt the reader has anticipated potential problems with the use of carrion to breed maggots, so let’s consider them:

The first beaver Sam gave me I simply stuffed, whole, into my largest bucket. The bucket produced an abundance of maggots but, not surprisingly, smelled pretty “ripe” during the last few days of “processing.” I now have five working buckets, so I chop each beaver carcass into five pieces. I line the bottoms of the buckets with litter from the poultry house (mostly oak leaves), lay in the beaver chunks, then pad with more leaves around and on top, and screw on the lids. (The loose leaves do not impede access to the carrion by the flies.) With this adjustment, I find that the processing time—the time from carrion addition until the maggots have reduced it to hair and bones—is greatly accelerated, and there is very little smell. Indeed, I catch a whiff only when I am working in the immediate vicinity of the buckets. (Suburban flock owners, however, would do well to seek free protein elsewhere.)
Curiosity seekers
The buckets would certainly draw dogs, foxes, raccoons, and other curiosity seekers if allowed access to them. Therefore this system is useful only where access can be denied. I use electric net fencing, and never have problems with raids on the buckets. Placing the buckets inside permanent predator fencing would work as well. Only once have I had a visit from buzzards, drawn to that first heavily scented bucket. They hung around most of a day, clearly intoxicated by the heady aroma, but frustrated they could not get at its source. They finally gave up and lumbered into flight, never to return. I think the lack of repeat visits has much to do with the greatly reduced odor in the buckets these days.
“Breeding flies”
Many people have objected to my system because it amounts to a deliberate breeding of flies. Let me emphasize that I am breeding fly maggots, not flies, and actually my methods should decrease the ambient fly population. Imagine there are 100 female flies in the vicinity, and I manage to convince 20 of them that my carrion buckets are the best place imaginable to lay their eggs. They do so (rather than laying them elsewhere). But not a single fly larva gets to pupate and hatch—my sharp-eyed chickens see to that. I’ve just reduced the local fly hatch by 20 percent.
Naturally my reader, however dedicated to the ideal of self-sufficiency, will worry about the potential for generating disease out of carrion worked by maggots. I am duty bound to pass on industrial-strength warnings I’ve received to that effect: There is a condition the old-timers called “limberneck,” which turns out to be paralysis caused by botulin poisoning. My friends who warned me about limberneck insisted that it could be caused by maggots ingested by chickens from any source. However, in all the links they sent, the references actually described the condition associated only with spilled feed which had become wet, had soured and begun working with maggots, and then been consumed by the birds. Sounds to me as if the botulism bacterium was growing in the soured feed mash, not in the maggots. In any case, I have always avoided using a grain mash as a maggot breeding substrate. However, I fed carrion-bred fly larvae the entire fly season last year, and this season I have honestly lost track of the number of beaver carcasses I’ve put through my buckets—and I have not had a hint of a disease problem. Neither has my longtime mentor Joel Salatin, who follows beef cattle on his pastures with a big flock of laying hens, who scratch apart the cowpies for the maggots growing in them. Based on such solid experience, I conclude that the homestead flock owner need not fear disease if he chooses to tap into this rich source of free protein.