Chapter
10
WESTERN
RESEARCH ON INSECTS AS FOOD AND ANIMAL FEEDSTUFFS
Introduction
It is well-known
that insects are an attractive and important natural source of food for many
kinds of vertebrate animals, including birds, lizards, snakes, amphibians
(toads, frogs, salamanders), fish, Insectivora and other mammals (McHargue
1917; Frost 1942, pp. 62-63; Brues 1946, pp. 399-407, 418; and many
others). McHargue cites a U.S.
Biological Survey investigation of the stomach contents of 14 species of wild
birds revealing that approximately 50% of the annual food consumption consisted
of insects. McHargue notes that since
insects are available for only about half the year, the wild bird diet consists
almost entirely of insects during the seasons when they are present. McHargue states (p. 634): "The avidity
with which domestic fowls, when allowed to range, seek insect food is familiar
to all, and it is a well-known fact that poultry thrive best when they
have access to this kind of food."
Thus, while looked
upon in the West with disfavor as food for humans, insects have attracted
occasional research attention as feeds for domesticated animals, particularly
poultry, swine, freshwater fish, and certain zoo, laboratory and household
animals. The vast majority of studies
in the West have dealt with the nutritional value of muscoid Diptera
larvae/pupae used to recycle nutrients from poultry manure or other organic
wastes as a high-protein source for broiler production.
Redford and Dorea (1984)
determined the water, ash, total nitrogen and fat content for the worker and
soldier castes of nine species of Brazilian termites, and then compared these
values with those from other species of termites, ants and 22 other species of
terrestrial invertebrates. The tabular
data include some species used as human food in various regions of the
world. Studier and Sevick (1992)
reported the live and dry mass, water content, nitrogen, sodium, potassium,
magnesium, calcium and total iron concentrations for representatives (mostly
adults) of 16 orders of insects (360 species) occurring in south-central
Michigan. The tabular data include
families and a few genera and species that are used somewhere as human food. The authors report that, compared to
published nutritional requirements (when meeting caloric requirements) for
growth and reproduction in birds and mammals, insects are excellent sources of
nitrogen, potassium and magnesium, highly variable sources of sodium and iron,
and, rarely, adequate calcium sources.
The book by Slansky and Rodriguez (1987) is a valuable
source of information on the nutritional ecology of many insect groups that are
important as human food.
Whole dried insects
are about 10% chitin, a carbohydrate polymer found in invertebrate
exoskeletons, protozoa, fungi and algae.
The chitin presents problems of digestibility and assimilability in
monogastric animals, but it, and its derivitives, particularly chitosan,
possess properties that are of increasing interest in medicine, industry and
agriculture. Goodman (1989)
listed some of its capabilities: significantly reducing serum cholesterol,
acting as a hemostatic agent, enhancing burn and wound healing, acting as an
anticoagulant, protecting against certain pathogens in the blood and skin,
serving as a non-allergenic drug carrier, providing a high tensile-strength
biodegradable plastic for numerous consumer goods, enhancing pollutant removal
from waste-water effluent, improving washability and antistatic nature of
textiles, inhibiting growth of pathogenic soil fungi and nematodes, and
boosting wheat, barley, oat, and pea yields as much as 20%. Investigators are
calling chitin, with its abundance, toughness and biodegradable properties, the
polymer of the future, according to Goodman.
While insects and fungi have the highest ratio of chitin to body mass
and global bioproduction is enormous, the primary source to date has been waste
products generated by the shellfish industry. From the foregoing account by
Goodman, it seems apparent that if protein concentrates from insects become
acceptable and produced on a large scale, the chitin byproduct could be of
significant value.
Ritter (1990)
discussed cholesterol in insects. Like
other animals, most insects are approximately 0.1% sterol (i.e., 1 mg sterol/g
tissue), but insects are unable to synthesize sterols de novo and must
obtain them exogenously from the diet or from symbionts. Ritter describes the metabolic conversion,
or lack of conversion, of various sterols to cholesterol. Some insects,
including edible species such as the honey bee, Apis mellifera, and the
leaf-cutter ant, Atta cephalotes isthmicola, contain no
cholesterol. Through diet alterations
in which the Δ5-sterols are replaced by other sterols, some other species,
which are edible could be produced which contain little, if any,
cholesterol. Ritter's research has
demonstrated this with the corn earworm, Heliothis zea, and it might be
done, for example, with the cricket, Acheta domesticus, by feeding a
diet rich in alfalfa sterols (i.e., Δ7-sterols).
DeFoliart (1991)
reviewed the available data on insect fatty acids and reports that the
proportions of saturated/unsaturated fatty acids are less than 40% saturated in
most edible insects, grouping them with poultry and fish. Another notable feature of insect fatty
acids is the very high ratio of the polyunsaturates, linoleic and linolenic
acids, higher in general than found in poultry and fish.
Coleoptera
McHargue (1917)
conducted proximate and amino acid analyses on two species of insects, one of
which was the June bug, Lachnosterna sp. (Family Scarabaeidae) (Phyllophaga
= Lachnosterna). It is stated that
analysis showed "such a large percentage of protein present in the dry
state," that further studies were conducted, but McHargue doesn't give the
percentage found. Data are presented on
the amino acid content in comparison to beef roast and turkey white meat. Lachnosterna was equivalent to the meats
in lysine (8.02% of analyzed nitrogen), slightly lower in arginine (11.53%) and
cystine (0.35%) and had only about 50% as much histidine content (6.57%).
Davis (1918) noted
that the grubs and beetles of Lachnosterna are eagerly preyed upon by
numerous species of birds and mammals, particularly by crows and
blackbirds. Crows often follow the
plough, eagerly picking all exposed grubs.
Davis cites the U.S. Biological Survey having found these insects in the
stomachs of 78 species of birds and two species of toads. Among native mammals, the skunk is probably
the most valuable in eating qrubs.
Farm fowls, especially
turkeys but others also are fond of both grubs and adults, and the domestic hog
"is the most efficient of all grub destroyers where it can be
utilized" (Davis, pp. 12-13).
According to Davis, the practice of "hogging off" corn, thus
saving the expense of harvesting and marketing, is a good preventive control
for white grubs as well as cutworms, wireworms and other soil-infesting
insects. Advantages include not only
(l) control of these insects, but (2) utilization of their food value, and (3)
manuring of the land.
Davis cites an example
of control in which l00 pigs and 8 sows were turned into a heavily infested l0-acre
cornfield in Illinois and destroyed 99% of the grubs within 27 days. Assuming 34.6 grubs per hill (the number at
the beginning of the experiment) and the number of hills per acre at 3,556, the
pigs destroyed approximately l,217,083 grubs, or 11,278 grubs (24 lbs) per
animal. The pigs suffered no ill
effects.
Turkeys search
diligently for grubs, and Davis states that he has seen infested timothy and
sod fields thoroughly scratched up by these birds. Chickens don't search unplowed fields but if allowed the run of
the field during ploughing or cultivation they eagerly pick up every grub and
beetle exposed. Davis cites an instance
in Iowa where a flock of about 150 chickens, encouraged to follow the plough,
harrow, and cultivator, practically eliminated the grubs in a badly infested 15-acre
field. Davis notes that portable
poultry houses have been used in Europe to allow foraging for the European May-beetle
grubs.
According to Davis,
there are no authenticated reports of harmful dietary effects on either hogs or
poultry from feeding heavily on grubs or adult beetles. European tests revealed no difference in
taste of eggs from grub-fed hens and others; in fact, the former had
better yolks "for thickening and were worth three of the others to color
sauces." The only unfavorable
result was "in the case of dried beetles mixed with bread and potatoes,
which proved too exciting for the older fowls."
Davis notes objections
raised to the use of hogs, mainly to pasturing on sod land: l) Need for hog-tight
fences - Davis believes the cost is quickly recouped through the value of
the grubs as feed; 2) Rooting up of pasture land - to which Davis says
the overturned sod reseeds itself the following season with no ill effect other
than a roughing of the surface, which is of little significance; 3) Possible
infection with the giant thorn-headed worm, Echinorhynchus gigas,
an intestinal parasite of hogs, and of which the white grub is an intermediate
host. According to Davis, there is no problem in fields where hogs have not
pastured within the past three years.
Brood sows should be prevented from running in fields that are likely to
contain infected grubs and in which hogs have pastured within the previous
season or two. Less care is needed
relative to hogs being fed for market as they will probably be slaughtered
before the worms become damaging. Davis
(pp. 23-24, his Fig. 14) provides a three-year schedule for using
hogs to harvest grubs and prevent crop damage.
Davis states that there is an average of 106,680 grubs per acre in
infested areas, and that their weight during the fall of their destructive season
averages 1 gram (adults weigh slightly less); thus an infested acre contains
approximately 235 lbs of grubs. Davis
(pp. 3-11) provides information on taxonomy, life cycles, etc.
Finally, Davis
presents the results of proximate analyses (% of fresh weight) of Lachnosterna
grubs and beetles (p. 20):
Grubs Adults
Moisture
70.0 60.4
Crude fat
3.1 4.0
Crude protein 11.1 20.1
Crude fiber
1.6 8.7
Crude ash
2.0 1.6
N-free extract
(carbohydrates) 2.3 0.3
Cotton and St. George (1929, p. 4)
summarized the early use of the meal worm, Tenebrio molitor (Family
Tenebrionidae), as animal feed, stating that it was introduced into Chile
solely for rearing the larvae as bird feed.
In aquariums and zoological parks, they were in great demand for feeding
small birds, amphibians, reptiles, insect-eating mammals, fish and
carnivorous arthropods. According to
Cotton, a fish-bait vendor told him that "he could use 'half a
billion' of them [mealworms] annually."
Cotton cites early references, as early as 1721, on their use as bird
feed in Europe and summarizes his own extensive biological studies on rearing
them.
Fleming (1968, pp. 3-4)
notes that many native birds and mammals feed readily on adults of the Japanese
beetle, Popillia japonica Newman (Family Scarabaeidae). He cites a U.S. Bureau of Biological Survey
report in which stomach contents of 16 of 31 species of birds examined
contained beetle remains. Grackles ate
more than other birds; all 29 grackles examined had eaten beetles and the
beetles constituted 66% of their stomach contents. Chickens, turkeys, ducks and
guineas feed readily on beetles and these along with the grackle, European
starling, crow and gull (Larus spp.) dig up and devour large numbers of
grubs in heavily infested areas, especially when fields are being plowed and
grubs are close to the surface in grasslands.
Among native mammals, skunks are the most diligent predators of the Popillia
grubs. The common toad (Bufo
lentiginosus) eats many beetles.
Hogs have long been known to gorge themselves on grubs.
Fleming cites three
sources in stating that proximate analyses of the beetles revealed 67.4%
moisture, 22.1% protein, 2.1% fat, 1.5% ash, 6.6% crude fiber, and 0.3%
nitrogen-free extract.
With space flight as
well as planet-side food production in mind, Kok (1983)
proposes to apply automated industrial technology wherein substrate is
converted to insects in a manner similar to single cell protein
production. He explores several
possible system types and operating methods using the concept of packed beds
for insect incubation, growth and reproduction and concludes that the concept
is feasible. The drug store beetle, Stegobium paniceum, is the
experimental animal used in the investigation.
Kok et al (1988)
report that it is technically feasible to mass-produce insects for human
consumption by using industrial methods.
The test organism was Tribolium confusum (the confused flour
beetle). The authors describe a semi-continuous
process based on the use of a single, batch-fed plug flow reactor and
three basic unit operations. The
material passed through the reactor in four streams of small, segregated
batches with a phase lag of 2 days between them. The reactor performed four major functions corresponding to the
four streams; 1) feed conditioning, 2) feed conversion, 3) dormant stage
incubation (eggs, pupae) and 4) propagation (egg production). The process consists of two major
"cycles," conversion and propagation. The three unit operations are sifting, air classification and
solids mixing. Bread, sphagetti sauce
and hot dog weiners were prepared with the product pupae. These were found to
be palatable by volunteer consumers.
Kok et al (1991)
report the results of opportunistic sampling of the system described in
previous papers. Samples were analyzed
for moisture, ash, protein and fat, and mass balances were then calculated for
these components. Carbohydrate was
found by difference. The objectives of
nutrient incorporation and fat generation were partially met, but overall yield
of the process was rather low, according to the authors. "Process losses
were dominated by losses incurred during the organism propagation cycle;
nitrogen was lost in organism wastes such as larval exuvia." Results of the study will be used in
designing a second generation process.
Weissling and
Giblin-Davis (1995) tested several artificial diets as alternatives to
decomposing pineapple for culture of Rhynchophorus cruentatus (Fabr.)
larvae. The most suitable diet for
larval growth and survival was a combination of canned pineapple, oats,
sucrose, molasses, brewers yeast, Wesson's salts, vitamins and
preservatives. Poor growth and survival
were obtained on diets not supplemented with brewers yeast. It was found that
larvae would construct a cocoon only when placed in sugarcane stem. Sugarcane
appeared to contribute little to continued growth of maturing larvae and
probably is nothing more than a source of fiber for construction of the cocoon. Although the motivation for this study
pertained to the vector potential of R. cruentatus for the red ring
nematode, Bursaphelenchus cocophilus, the authors state:
. . . although we are aware of no
human consumption of R. cruentatus larvae in the U.S., larvae of R.
palmarum, R. phoenicis, and R. ferrugineus . . . are considered
delicacies by some [in Africa, Asia, Latin America]. The culture of R. cruentatus on artificial diets could be
a potential advancement in developing a niche for consumption of our indigenous
species by palm weevil gourmets or feeding burrowing owls in captivity.
The authors note that, unlike some other Rhynchophorus species, R.
cruentatus is not considered a major pest of palms, but it will attack
transplanted or otherwise stressed ornamental palms; in Florida it is sympatric
with the native cabbage palmetto, Sabal palmetto, which, because of its
low cost, natural abundance, and high transplanting survivorship, is often used
as mature specimens in landscaping.
Diptera
In situations where
poultry manure is not usable as fertilizer in the immediate vicinity where
produced, its disposal poses problems of odor, fly production and N
contamination of soil and water.
Various fly species have received experimental attention for their
ability to recycle poultry and other animal manures into useful feed products
for poultry and livestock. Hodge (1911) calculated that a pair of
house flies, Musca domestica L. (Family Muscidae), starting in April
could produce enough progeny by August, if all survived, to cover the earth
with a layer of flies 47 feet deep.
Although, as pointed out by DeFoliart (1975), this is an
ecological absurdity, it does indicate the tremendous reproductive potential of
some insects. Lindner (1919) appears to have been the first to suggest
that house fly larvae might be used to recycle organic wastes, human waste
specifically, to produce protein and fat as a useful byproduct.
Rodriguez and Riehl (1959)
conducted an experiment to determine whether cockerels could provide fly (Musca
domestica) control in manure under chickens housed in wire cages off the
ground. They described their rationale
thusly:
Young chicks instinctively scratch
and search every bit of surface within their reach constantly and industriously
looking for food. If growing chicks
were allowed to scratch in the droppings under the wire cages, would their
activities control flies? If they did,
what management practices would be useful in obtaining optimum performance?
Impressive control of M. domestica breeding was demonstrated in
a flock of 200 chickens using one cockerel per 10 hens in cages. In four
instances larvae were found in spots where the manure was very wet and hard for
the chicks to work; no pupae were ever found, however, suggesting that larvae
which the chicks did not find in the manure were caught as they left to seek
dryer areas for pupation.
In followup research, Rodriguez
and Riehl (1962) demonstrated control of flies (M. domestica)
by use of cockerels on commercial poultry ranches in southern California. They
reported reductions to zero, in some cases, of fly larvae and pupae in chicken
manure under cages with a raised wire mesh floor when cockerel chicks were
released on the ground. Control was
maintained with ratios of 20 to 100 hens in cages per one cockerel on the
ground. The authors describe management
practices favorable to successful fly control by the chicks. In the laboratory, baby chicks only 1-2 days
old were found to peck instinctively at larvae and pupae although they were
unable to pick them up. At 3 days of
age the chicks ate 100 larvae or pupae per chick per day and by 15 weeks of age
were averaging 8,000 or more per day.
The consumption of the flies (200 g/day) was higher than the consumption
of mash or grain on a free-choice basis.
Under ranch conditions, feed was supplied in the evening for the first
few days but not thereafter unless fly breeding was completely eliminated. At a rabbitry with 175 rabbits, control of
fly larvae and pupae was obtained with one cockerel per five rabbits.
Calvert and colleagues
at the U.S. Department of Agriculture were one of two groups which began
research in the late 1960's on the use of M. domestica for recycling
poultry manure into a high-protein feedstuff for poultry. Calvert et al (1969a) analyzed
pupae produced in CSMA fly medium and found a crude protein content of 63.1%
and fat content of 15.5% (Table 1; see authors' Table 1). Amino acid analysis indicated a protein
quality similar to that of meat and fishmeal; fatty acid analysis showed a
pattern similar to that of some fish oils, although the pupal fat content was
higher. Ash content was lower than that
of fish meal. When house fly pupae were
incorporated into a practical chick starter diet, replacing soybean meal, the
chicks gained significantly more weight than chicks fed the soybean meal diet
during a two-week experiment. The
increase in weight gain was due to an increase in feed consumption as feed-to-gain
ratios were similar in the two qroups.
Relative to recycling
poultry manure, Calvert et al (1969b) reported in a brief
abstract that fresh hen excreta will support a density of 3 pupae per gram at
temperatures of 23 to 26 C, and at this density the feces loses about 20% more
moisture than feces without pupae. With
a moisture content of only about 46%, the feces is loose, crumbly in texture,
and essentially odorless.
Calvert et al (1970)
presented data to support the seeding rate of 3 eggs per gram of fresh excreta
as the optimum seeding rate, and described equipment designed to simplify
collection of pupae from the processed excreta. A seeding rate of 1.5 eggs per
gram of excreta produced the largest pupae (ave. of 16.5 mg), highest survival
(85.1%), and a total pupal weight of 4.23 g from 200 g of excreta in 8 days. A seeding rate of 4.5 eggs per gram of
excreta yielded the smallest pupae (10.0 mg), lowest survival rate (44.4%), and
lowest total pupal weight (3.87 g) (although this seeding rate did result in
the greatest loss of moisture and thus weight, as well as nitrogen reduction in
the fecal samples). At a seeding rate of 3 eggs per gram of excreta (the rate
selected as best), pupal weight averaged 12.0 g, survival 66.4%, and total
weight of pupae 4.55 g.
Regardless of seeding
ratio, odor was reduced to an unobjectionable level within 4 days, and the
excreta were reduced to an essentially odorless, friable material within 8
days. The investigators suggest its
use, with additional drying and pelleting, as a soil conditioner. The pelleted material was found to disintegrate
rapidly with the addition of water, and without renewing the obnoxious odor of
the fresh excreta.
Morgan et al (1970)
re-described and illustrated the pupal harvest apparatus described previously
by Calvert et al (1970) (Fig. 1; see authors' Fig. 1). Fresh poultry feces, 10-12 lbs, were
placed in the center section of the top box to a depth of 2.5 to 3 inches; the
narrow side sections served as air vents for release of the ammonia
accumulating below. The device was kept
lighted from above to prevent the negatively phototactic larvae from wandering
upward in search of pupation sites. By
the sixth day, at 68-80° F, most of the
larvae had passed through the 1/8-inch hardware cloth floor to the tray
below and wriggled through the l/16-inch fiber-glass screen to the solid
floor to pupate. The few particles of
fecal material that dropped through the hardware cloth were retained on the
fiber qlass screen.
Morgan et al note that
the excreta of White Leghorn laying hens average 0.25 to 0.40 lbs/day. Thus, the daily production of 100,000 layers
ranges from 12.5 to 20 tons and creates an enormous disposal problem resulting
from odor and water pollution. Morgan
et al believe that, from the excreta of 100,000 hens, 500 to 1,000 lbs of pupae
can be produced daily while reducing the excreta to a semi-dry, crumbly
waste suitable as a soil conditioner.
Calvert et al (1971)
conducted analyses and feeding trials to determine the value of newly emerged
house flies as a protein source for chicks.
The fresh flies contained 69% moisture; the dried material contained 75%
protein and 7% fat. In feeding trials
to 3 weeks of age, the fly meal slightly improved chick growth and there was
little difference in feed/gain ratios compared to chicks fed a soybean meal
diet. Thus, the adult house fly is also
a good protein source for the young chick. These investigators also tested the
digested manure for chick growth, but growth was substantially less than for
chicks fed the soybean meal diet.
The second group
initiating research on the house fly in the late 1960's was at Colorado State
University. In a brief abstract, Miller
and Shaw (1969) state that of five species tested for their ability
to grow and reproduce in fresh poultry manure, Musca domestica and Muscina
stabulans (Muscidae) were most promising. M. domestica developed from egg to pupa in 56 days at 37° C.
The larvae removed about 80% of the organic matter from fresh poultry
manure, and reduced the moisture content of the manure from 75% to 50% in 5-6
days. No experimental methods are
described in the abstract.
Miller (1969)
discusses the disposal problem, pointing out that fresh manure is heavy,
containing about 75% water, and that the labor needed to move it from points of
accumulation prohibits its use as a fertilizer. Such manure accumulations offer breeding sites for wild flies,
thus creating a sanitation problem.
Miller briefly describes methods of managing the fly breeding colony and
harvesting pupae, presents tables of data on proximate and amino acid analysis
and mineral content of dried fly pupae, weight gains and feed efficiency on
broiler diets containing fly pupae, and analysis of fresh and digested manure,
but gives no experimental methodology.
Leinati et al (1971)
reported that infestations of Hypoderma sp. (Hypodermatidae) in the
backs of cattle on mountain pastures can be reduced by allowing cattle and
poultry (chickens and turkeys) to graze together on the same pastures. The poultry devour grubs after they drop to
the ground for pupation.
Teotia and Miller (1970a,b)
presented brief abstracts of work that was published in full later. Teotia and Miller (1973a)
describe methods of managing the breeding colony, conducting larval density,
humidity and temperature studies, pupal harvest (by flotation), and production
under caged layers. They found the best
seeding rate to be 3 g of fly eggs per 4 kg of fresh manure (Table 2; see
authors' Table 1]) at 27 C and 41% RH.
This seeding rate resulted in the highest total weight of pupae
harvested (76 g), highest percentage of manure lost in digestion (51.3%), and
lowest weight of manure harvested (1,949 g).
It took 8 days at 27°C and 41% RH. At these temperature and humidity
conditions, moisture in the manure was reduced from 78.5% to 55.0% by the
aerating action of the larvae and decomposition of the manure. Teotia and Miller also used fly eggs and/or
larvae seeding to digest the manure under caged birds. This worked fairly well, but temperature
must be kept above 20 C or larval development is inhibited.
Teotia and Miller (1974)
conducted proximate and amino acid analyses on house fly pupae and obtained
values similar to those of Calvert et al (1969) except that fat content was
lower and ash content higher than in the former study. These differences may have been due to the
different rearing media employed, Teotia and Miller rearing their larvae in
poultry manure while Calvert et al used CSMA fly medium. In the feeding trials, day-old single
comb white leghorn chicks were fed to 4 weeks of age on house fly pupae with or
without addition of a B vitamin and trace mineral supplement. Final body weights and feed/gain ratios of
chicks fed the experimental diets and the soybean meal control were not
significantly different. Unfortunately,
the fact that the house fly pupae were merely substituted for soybean meal made
the diets neither isocaloric nor isonitrogenous, which makes a direct
comparison impossible. It appeared,
however, that the pupae were a good source of B vitamins and trace
minerals. The authors also conducted
proximate and mineral analyses of fresh and digested manure. In feeding trials with manure containing
pupae, chick growth was comparatively poor on the digested manure/pupae
mixture.
Teotia and Miller (1973b)
conducted a second set of feeding experiments in which the flaws in the first
experiments were corrected by adjusting the levels of the other dietary
ingredients so that the experimental and control diets were isocaloric and
isonitrogenous. Also, fast-growing
broiler chicks were used which should be more sensitive in detecting
differences in protein quality. Lastly,
this trial was of 7 weeks' duration as opposed to 4 weeks in the earlier
experiments. As before, the
experimental diet was not supplemented with a B vitamin or trace mineral
mix. After 7 weeks there were no
significant differences in weight gain or feed/gain ratios between the two
treatments. Unfortunately, the protein content of the diet was kept constant
throughout the experiment and since the NRC (1977) requirement for broiler
chicks changes from 23% at Day 1 to 18% at 6 weeks of age, the ability of this
experiment to detect anything but a major difference in protein quality was
compromised.
Miller et al (1974)
provide a summary table (Table 3; see authors' Table 2) showing results of
digestion of fresh poultry manure at a seeding rate of 1.0 g of fly eggs/kg of
manure. Approximately 80% of the
organic matter was used by the larvae during their development. About 58% of the moisture was lost while
mineral content was not changed. The
manure residue contained about 15% protein after pupae were removed. Physically, the manure was somewhat granular
and could be dried readily because of the increased surface area, small
particle size and improved aeration.
Hale (1973)
reported that dried larvae of the soldier fly, Hermetia illucens (L.)
(Family Stratiomyidae) contained 45.2% crude protein and 31.4% ether
extract. Amino acid analysis showed the
larvae to be higher in methionine (1.9% of crude protein) than either soybean
meal or meat scraps (both 1.4%). In a two-week feeding trial, there were no
significant differences in weight gained or feed/gain ratio of chicks fed a
diet containing either dried Hermetia larvae or soybean meal as the
major protein source. The chicks fed
the soybean meal diet consumed significantly more feed, however. The author speculates on several possible
causes for the apparently lower palatability of the larval diet: high content
of larval meal (35% of the diets were composed of larval or soybean meal,
respectively); somewhat higher fat content in the larval diet (chicks on the
soybean meal may have compensated by consuming more total feed); and, higher
crude fiber content in the larval diet.
Hale notes that H.
illucens larvae are large, full-grown larvae averaging about 250 mg
in weight compared to about 25 mg for house fly pupae. The larvae are found in a variety of moist
situations high in organic matter, such as decaying fruits and vegetables, damp
feed grains either ground or whole, and animal wastes in and near animal
quarters. About two weeks are required
to reach maturity, and the larvae are very "hardy."
Beard and Sands (1973)
tested larvae of several species of Diptera for their ability to degrade both
anaerobic and aerobic poultry manure.
They found that all species tested except Fannia canicularis (L.)
(Family Muscidae) and unidentified species of Sphaeroceridae (small dung flies)
failed completely in anaerobic manure. Fannia
and the sphaerocerids thrived in aerobic manure, but Beard and Sands concluded
that their small size and their behavior limit their potential practical value
in degrading manure. The house fly, M.
domestica showed the greatest adaptability for managed degradation of
aerobic poultry manure, while larvae of several other species didn't grow well
enough to warrant further investigation, i.e., Phormia regina (Meigen), Protophormia
terrae-novae (Robineau-Desvoidy) and Phaenicia sericata
(Meigen), all of the Family Calliphoridae, and Sarcophaga bullata Park
(Sarcophagidae).
Beard and Sands
provided data on a number of factors affecting degradation of poultry manure by
the house fly. 1) Genetic variability offers the opportunity of selecting
strains that are better degraders of manure.
Seven strains were evaluated on the basis of mean survival-size
scores, including two flightless strains, but none were better than the strain
already adapted to the laboratory. 2) There appeared to be no difference in
fecundity (and therefore dietary protein for egg development) between
sugar/manure-fed flies and sugar/milk-fed flies. 3) When offered a
choice between manure and dog food moistened with yeast suspension as an
oviposition medium, flies discriminated against manure, but in the absence of a
better alternative, manure was acceptable. 4) Measured by survival-size score,
dog meal-yeast medium was slightly better (significant at 5% level) than
manure as a larval development medium. 5) Size-survival scores showed
that flies do better (larvae) in fresh than in aged manure. 6) Rate of oxygen
consumption is a gross measure of metabolic activity of organisms growing in
manure. Oxygen was utilized at
essentially the same rate by manure with larvae alone, with microorganisms
alone, or with both. 7) Bacteria rather than fungi appear to be the dominant
constituents of manure microflora. Some
bacteria may be detrimental to larval development while yeasts appear to play a
minor role as a dietary source for larvae. 8) Although larval activity reduced
N, anaerobic decomposition did also, almost to the same degree. This and the results of respiration studies
suggest that larvae share manure nutrients with microorganisms and that
reduction of N levels is not solely attributable to larvae. The main contribution of larvae appears,
therefore, according to the authors, to be mechanical aeration resulting in
increased loss of ammonia, water vapor, and other gases; hence favoring aerobic
organisms, eliminating offensive odor, and dehydrating the medium. The authors discuss these and other factors
as they interrelate in manure degradation.
Pupal harvest by flotation isn't good because it doesn't retain the dry
condition of the residual manure. The
authors suggest that hens could be used to pick larvae and pupae from the
manure.
Papp (1975)
conducted experiments to determine the economic feasibility of processing pig
manure by house fly larvae. Production yields were as high as 8.05% compared to
a theoretical maximum of 10%, results considered equivocal by the author.
Chemical assays by Dashefsky
et al (1976) showed pupae of Musca autumnalis DeGeer (Family
Muscidae) to contain a high percentage of phosphorus, 5.73% of dry weight. In a 15-day feeding trial, the
phosphorus was found to be at least 92% biologically available to White Rock
chicks, making the pupae at least of the same quality as most of the
commercially sold dicalcium phosphate sources.
Analysis of dried pupae meal revealed a crude protein content of 46.5%.
Newton et al (1977)
conducted a digestion trial on 5-week-old barrow pigs to evaluate
dried, ground soldier fly larvae, H. illucens, as a dietary supplement
compared to soybean meal. The larvae
were collected from cattle feces and urine slurry. Proximate composition and calcium and phosphorus content of dried larvae was 7.9% moisture,
and, on a dry matter basis: crude protein 42.1%, ether extract 34.8%, crude
fiber 7.0%, NFE 1.4%, ash 14.6%, calcium 5.0% and phosphorus 1.5%, respectively
(see authors' Table 2 for these data and data on digestion trial diets). Apparent digestibilities for the larval meal
diet and (in parentheses) the soybean meal diet were: dry matter 77.5 (85.3),
nitrogen 76.0 (77.2), ether extract 83.6 (73.0), crude fiber 53.8 (49.2), ash
45.2 (61.7), NFE 84.7 (91.2), calcium 38.9 (39.3), and phosphorus 24.5 (51.3). Values for dry matter, nitrogen, ash and NFE
were significantly greater (P <.05) for the soybean meal diet than for the
larval meal diet. Pigs did not discriminate against the larval meal diet,
indicating good palatability. The
authors conclude that further studies are needed to determine the optimum
levels of larvae in livestock diets.
Larvae would be especially valuable for their amino acid, ether extract
and calcium content, but because of the high ash and ether extract content
might be better utilized at lower levels than those used in these trials. Booram et al (1977) reported
the results of additional investigations on the recycling of swine manure by H.
illucens.
Calvert (1977)
reviewed the use of both unicellular organisms and invertebrates for protein
production from animal and municipal wastes, including algae, yeasts, fungi,
mixed cultures of bacteria, house fly larvae and earthworms.
Ocio et al (1979)
provided proximate and amino acid analyses of house fly larvae grown in
municipal organic waste (MOW). Feed
trials were conducted with three diets that were isocaloric and isonitrogenous:
1) standard corn-soy diet, 2) fish meal substituted for some of the
soybean meal so that 9% of the dietary protein was from fish meal, and 3) house
fly larvae substituted for some of the soybean meal such that the larvae
furnished 12% of the dietary protein.
There were no significant differences in weight gain or feed/gain ratio
in birds from any of the three treatments after 4 weeks.
Abdel Gawaad and Brune (1979)
tested a mixture (1:1) of dried, ground larvae of Phormia regina (Family
Calliphoridae) and M. domestica as the high-protein source for
broilers fed through the fourth week of age.
Amino acid compositions of the two fly species were similar (data are
given by the authors). Lysine content
of the larvae-meal was high, even higher than in fish meal, but
methionine was low. There were no
significant differences in final weight or feed conversion efficiency of chicks
fed the experimental larval meal diet and the control chicks fed the soybean
meal diet. The investigators observed a
significantly lower weight of feathers in the larval-fed group, which
they suggest may have resulted from the low methionine in the diet. As to carcass composition, the dry matter
content of the breast muscle and the drumstick of the test animals was
significantly greater than in the controls, which the authors attribute to a
significantly higher fat deposition, while protein accumulation was lower in
the test animals. The ash content in
the meat and bones showed no marked difference. In an organoleptic test on the stewed breast meat, no marked
effect on color, smell or taste could be detected.
Abdel Gawaad and Brune
mention a rearing procedure (not yet published) whereby one pair of flies
supposedly produces 190 billion flies from April to September; based on a fresh
weight of 0.023 g per full-grown larva, this would total 4.4 x 106
kg fresh weight or 1.2 x 106 kg dry weight, and about 0.6 x 106
kg of protein.
Koo et al (1980)
conducted studies on the face fly, Musca autumnalis (De Geer), reared in
cattle manure and allowed to pupate in sand.
The authors point out three biological advantages of this insect over
the house fly: 1) It's larger in size, face fly pupae averaging .03 g compared
to .025 g for house fly pupae; 2) Pupation occurs in 3 days following
oviposition at 41°C compared to 5-6
days for the house fly; and 3) Adult house flies are subject to epidemics of
infection with the phycomycete Entomophthoro muscae while there is no
record of face flies succumbing to this fungus. At the conclusion of feeding, face fly larvae, like most other
flies, void the intestine and seek a drier location in which to pupate making
it easy to harvest the pupae free of the manure in which the larvae have fed.
Proximate analysis
revealed 51.7% crude protein in the face fly pupae, which is less than that
found in house fly pupae. Crude fat content was intermediate compared to
reported values for the house fly while nitrogen free extract and fiber were
less than in the housefly.
Interestingly, face fly pupae contained 3 times as much calcium and
twice as much phosphorus as reported for house fly pupae. In feeding trials using Single Comb White
Leghorn chicks, in which dried pupae were directly substituted for soybean oil
meal to 4 weeks of age, there was a slight decrease in feed efficiency which
the authors attribute mainly to the lower gross energy value of the pupal meal
(4.284 kcal/g) compared to the soybean meal used (4.682 kcal/g). Microbial counts of the dried pupae were
well below the tolerances for human food as given by Powers (1976). The authors
conclude that dried, ground face fly pupae are a suitable source of protein in
poultry diets and that, microbiologically, they would be acceptable for human
consumption.
In feeding trials with
channel catfish and blue tilapia, manually collected black soldier fly larvae (H.
illucens) from poultry waste have shown promise as a feed ingredient for
commercial fish production (Bondari and Sheppard 1981). Taste tests
showed that the fish fed soldier fly larvae are acceptable to the
consumer. The authors note that,
because the larvae of this species can be produced from a wide variety of waste
materials, "production of larvae on a large-scale basis for fish and
animal feed will also have an impact on recycling of waste products."
Tests in an
experimental caged layer house demonstrated that soldier fly larvae (H.
illucens), in addition to offering a potential food source, provide house
fly and lesser house fly control and about a 50% reduction in manure volume (Sheppard
1983). The rate of self-collection
by the larvae indicated that a commercial operation with 20,000 hens could
harvest 540 kg of mature larvae per month during the summer.
E1 Boushy et al (1985)
discuss limitations inherent in the value of dried poultry manure (DPM) as
poultry feed and suggest (with a review of the pertinent literature) that the
use of organisms to break down the excreta, such as house fly larvae, earthworms,
or by means of fermentation, or upgrading by aerobic digestion and oxidation
ditch or algae culture are ways of converting the manure to a protein source in
animal diets. In DPM only about half of
the total nitrogen is true protein, the remainder being in the form of uric
acid which cannot be utilised by fowl and may even be toxic at levels above
1.07% in the ration. The low available
energy in DPM is also a problem. Relative to biodegradation of poultry manure
by house fly larvae, E1 Boushy et al note from literature sources that the
digested manure residue and pupae contain a high level of protein but a low
level of non-protein nitrogen. Pupal yields are 3.2% of the fresh manure
and about 4.0% on a dry matter basis.
The authors discuss the technological aspects of the different systems
of handling poultry manure, focusing on both the advantages and disadvantages
of each. For comparison of earthworms and pupae, the two main sources cited by
E1 Boushy (Fosgate and Babb 1972 and Calvert 1977) should also be consulted.
E1 Boushy (1986)
provides numerous tables and data on the world food supply and diets in the
developing countries, stating that diets of the inhabitants are generally
sufficient in calories, mainly from vegetable sources, and short in animal
protein. Increased consumption of
poultry is suggested as the best solution, considering that poultry meat is
most palatable and broilers are fast-growing, reaching a weight of 1.5 kg
in 7 weeks with a food conversion of 1.8.
The total volume of broiler meat produced in developing countries is
estimated to be 7 million metric tons per year, providing an estimated
consumption of 3 kg per capita per year. E1 Boushy advocates the development of
local industries, as opposed to home slaughter, partly because of better
utilization of byproducts such as manure and offal, leadinq to the
establishment of secondary rural industries.
According to E1
Boushy, poultry in the developing countries produce about 40.3 million metric
tons of manure per year, about 26.2 million tons of it from layers and 14.1
million tons from broilers. The use of
dry poultry waste as feed for ruminants, aerobic fermentation, or
biodegradation of the manure with organisms such as fly larvae or earthworms
are ways of upgrading the manure to supply feed products. In the case of house
fly pupae, based on a yield of 3.2%, a metric ton of manure can be converted to
32 kg of high-protein feedstuff.
This compares to 13.3 kg of dried earthworms per ton. The total of 40.3 million metric tons per
year could thus be converted to l.3 million tons of fly pupae.
Glofcheskie and
Surgeoner (1990) investigated the usefulness of Muscovy ducks in an
integrated program for control of house flies (M. domestica). In laboratory trials, ducks removed adult house
flies at least 30 times faster than commercial bait cards, coiled fly paper
rolls, fly sheets, or fly traps. The LT90
for ducks in 0.24m3 cages with 100 flies was 0.6 h compared to 15.3
h for the most effective commercial device.
In pens with calves, ducks survived for test periods of 12 weeks or more
without injury or feed supplement, and ingested a mean of 25 flies per 15-min
observation period when populations were low to moderate. The observed behavior is innate, suggest the
authors, as the experimental ducks had no previous experience with flies, yet
fed on them readily even when provided feed ad lib. One of the ducks penned with a calf was
observed to capture, on average, 23 flies per 32.5 attempts. Two (among several) advantages of ducks were
effectiveness against insecticide-resistent flies and elimination of breeding
sites by removing spilled feed. The ducks were also more economical than the
commercial control devices. The authors
estimate that under their local conditions a producer could make a profit of
$65 on 10 ducks by selling them at the end of the season, while the other
control devices range in cost from $171 to $455 for season-long fly removal.
At a midsize dairy
farm that kept unrestrained Muscovy ducks for fly control, the ducks stayed in
the vicinity of the barn and interacted well with animals and humans. In addition to feeding on adult house flies,
they also picked flies from the lower legs of cows, indicating that they were
also feeding on stable flies, Stomoxys
calcitrans (L.). The investgators
caution that ducks cannot be used in commercial poultry operations because of
disease hazards.
El Boushy (1991)
points out that a chicken ranch with 25,000 caged layers produces 2500 kg of
wet manure per day or 912.5 tons per year, thus creating a major problem of
waste disposal. Dry poultry manure is
not, of itself, recyclable as a good feedstuff for poultry because of its low
energy and high content of uric acid and non-protein nitrogen, neither of which
can be utilized by monogastric animals.
Research during the late 1960s and the decade of the 1970s, however,
showed that house fly (Musca domestica) pupal meal produced by larval
biodegradation of poultry manure is of high protein quality. In addition, digestion of the manure by
larvae converts it into an odorless, loose, crumbly product that can be easily
dried and used as a feedstuff.
Unfortunately, no practical large-scale method of separating the pupae
from the digested manure residue has been found. El Boushy suggests then that the most practical procedure is to
produce a mixture of pupae and manure residue, thus upgrading the latter to
reasonable feedstuff quality. He
describes how this could probably be economically accomplished with equipment
that is already in practical use on many large poultry farms.
Studies on the soldier
fly, H. illucens, appear to have solved the problem of efficient harvest
of pupae from manure under caged layers (Sheppard 1992, Sheppard et al 1992).
This non-pest species is proving to be an excellent manure management agent
that can produce large quantities of high-quality animal feedstuff, almost
completely prevent house fly development and reduce manure residue volume by
50%. Prepupal soldier flies are
self-collected as they crawl out of the manure basin seeking pupation
sites. They crawl up a 40° slope on one wall of the basin, into
a 1/2 inch slit in a 15 cm diameter PVC pipe at the top of the slope, then
crawl to a container at the end of the pipe (in the experimental facility, they
negotiated a 12-meter length of pipe).
The authors estimate that the value of the dried larval feedstuff
produced, savings in the cost of insecticide and manure removal and surface
application would net a small 20,000 hen egg producer an extra US $7,360. They state that the system should easily
adapt to swine waste management, and that soldier flies could be used to
degrade many other organic wastes.
In a second report on
use of Muscovy ducks for fly (M. domestica) control, Glofcheskie and
Surgeoner (1993) found that, in fly-proof calf pens, one duck per
pen reduced adult fly numbers by 96.8% and larvae by 98.7% compared to pens
without a duck. In an enclosed calf
room, fly reductions were 84% and 93% compared to times when ducks were not
present. In open areas of the dairy,
however, which permitted immigration and emigration of flies, reductions were
not statistically significant. Ducks reduced fly numbers on animals by 91% in
an enclosed swine farrowing room and by up to 86% in an open dry sow house. Female ducks were observed to consume flies
up to three times faster than did males.
Ducks had access to flies, water and wasted feed, and duck health was
maintained in most experiments without supplementary feedings. At the end of the tests, the least valuable
ducks were sold for twice their original cost ($4 vs $2), and, in addition,
cooperators saved $100 to $300 by not having to purchase fly control
chemicals. The authors emphasize that
the use of ducks must be considered a supplement to good sanitation. They
report that all of the cooperators indicated that they would use ducks in the
following season.
In a textbook based on
the use of some neglected vegetable and animal wastes as a poultry feedstuff, El
Boushy and van der Poel (1994) include a section on Dried Poultry
Waste under which they discuss biological conversion of layer manure by means
of house fly larvae, earthworms, aerobic fermentation, oxidation ditch and
algae.
Sheppard et
al (1995) add to information on their manure management system using the
black soldier fly. Their Abstract is duplicated below:
Indent margins
A manure management system for laying hens using the black soldier fly,
Hermetia illucens (L.) converted manure to a 42% protein, 35% fat
feedstuff, reduced manure accumulation by at least 50% and eliminated house fly
breeding. No extra facility or added energy was required. Mature larvae
self-harvested producing a feedstuff as they attempted to pupate. Optimal
feedstuff to manure dry matter yield was 7.8%. This insect occurs worldwide in
tropical and warm-temperature regions and can digest many biological wastes.
Homoptera
Hildreth (1830)
described an emergence of Magicicada (= Cicada) septendecim
(Family Cicadidae) (the "17-year locust") in 1829 in Ohio and
mentions their attraction as food for animals: "Hogs eat them in
preference to any other food; squirrels, birds, domestic fowls, etc., fattened
on them. So much were they attracted by
the cicadae, that very few birds were seen around our gardens during their
continuence, and our cherries, etc. remained unmolested."
Marlatt (1907)
lists more than two dozen species of native birds that feed on the periodical
cicada. He states that the English
sparrow (Passer domesticus) is perhaps its greatest enemy, but several
native species neglected other foods when cicadas were available. Fox squirrels eat them and chipmunks (Tamias
striatus) are very fond of them.
Cicada remains have been found in black bass, blue catfish and white
sucker. Marlatt cites a John Bartram
that hogs rooted up the ground a foot deep in search of cicadas and he quotes a Dr. Potter that great
numbers are "devoured by hogs, squirrels, all kinds of poultry, and birds,
which live and fatten on them."
Dogs become fond of them, according to a Dr. Phares (Marlatt, p. 104)
who also reported that they were "said to have killed a few hogs in Amite
County" in 1859.
Cicadas can be
collected by hand if it is done early in the morning or in late evening when
they are somewhat torpid and sluggish.
Marlatt (pp. 141-142) states that if collecting is
"undertaken at the first appearance of the Cicada and repeated each day,
the work of control will be facilitated by the fact that most of the insects
will be on young trees and within comparatively easy reach." Work for the protection of nursery stock in
Pennsylvania is cited in which more than 1,000 cicadas were collected per day
per collector. Despite the collection of 70,000 cicadas over a period of more
than two weeks, 05% of 240,000 peach trees were lost.
Hymenoptera
In the Prairie
Provinces of Canada, Alberta, Manitoba and Saskatchewan, because of the
uncertainty of winter survival of honeybee colonies, the bees are killed off in
the fall and restocked in the spring. Hocking
and Matsumura (1960), of the University of Alberta, reported that,
at the time of killing, colonies may contain from 1/2 to 5 lbs. of mature
capped brood (larvae/pupae), and they estimated that there are 132 metric tons
of this bee brood available annually.
The brood is a rich source of vitamins A and D, and analysis revealed a
protein content of 15.4% and 18.2% for mature larvae and pupae, respectively,
on a wet weight basis.
When brood was
prepared by either shallow frying in butter or deep-fat frying in vegetable
cooking fat and tested by a panel of Canadians, "Most reactions were
favourable and some were eulogistic; initial prejudice proved easier to
overcome than we had expected. When the
tasters were asked to compare the material to some more familiar food, those
most commonly mentioned were walnuts, pork crackling, sunflower seeds, and rice
crispies. In a later, larger taste
test, deep-fat fried, butter fried, and baked preparations were highly rated
while smoked, pickled, and brandied were much less preferred. There was a highly significant difference of
opinion (statistically) between men and women tasters regarding the three best
preparations, the men ranking deep-fat fried first and the baked third, and the
women reversing this. As described by
Hocking and Matsumura, cooking takes about 1 minute; the pupae swell up, turn
crisp and a golden brown color, and retain their form and integrity well.
Gary (1961)
investigated aspects of harvesting bee brood as food. To insure uniformity of larval age at harvest time, brood rearing
was concentrated in certain frames by confining queens in frames having queen
excluder walls. Every fourth day the
comb filled with eggs was removed from the cage and replaced by an empty brood
comb. Brood was allowed to develop
until most of the larvae were capped (9-11 days). Cells can be uncapped with a thin serrated knife, and larvae are
extracted easily and efficiently by spraying the comb with one or more jets of
water. Larvae are removed from both
sides of the comb and allowed to fall onto a cloth filter such as
cheesecloth. After the water is shaken
from the cells, the dark empty brood combs can be returned to the queens. The queens prefer them and they encourage
maximum egg production. The author
states that it is possible to harvest at least one pound of larvae per week
from each producing queen.
Ryan et al (1983) evaluated adult honey bees (Apis
mellifera L.), collected after honey harvest in Canada, as a raw material
for protein extraction. Fluidized bed
dried bees were 36.3% of their fresh weight, vacuum dried bees were 33.5% of
fresh weight. An average of 2.14 kg of
fresh bees, thus equivalent to 0.717 kg of vacuum dried adults, were removed
per colony. The proximate composition
of the dried bees was 49.8% crude protein, 7.54% total lipid, 27.1% sugar and
11.1% chitin. As approximately 20% of
the bees were not recoverable, being wedged in the comb or contaminated with
debris, the investigators estimated that each discarded colony contained the equivalent
of 0.879 kg of vacuum dried bees composed of 0.440 kg crude protein. Several
factors contributed to variations in the quantity of protein precipitated, but
the authors note that these factors would all be present in large scale protein
recovery operations. The average
quantity of precipitate recovered was 18.1 g dry weight/100 g fresh bees. The
precipitate was 66.3% crude protein, 9.4% total lipid and 7.9% ash.
Ryan et al separately
extracted heads, thoraces and abdomens of the bees and observed qualitative
differences in the color and odor of the precipitates. Amino acid analysis of the three protein
fractions found all of them nutritionally deficient in the sulfur-containing
amino acids. Chemical scores relative
to whole egg protein (FAO 1970), calculated by the methodology of Oser (1951),
were found to be 77 for bee heads, 84 for thoraces and 81 for abdomens. These compare with the score of 88 reported
by Oser for beef and fish muscle protein and of 80 for yeast. Tryptophan was not included in the analyses
by Ryan et al, but they state that it is not expected to be limiting and
adequate tryptophan would elevate bee scores approximately 2 points each. Also, whole body scores will be greater than
the component scores as different amino acids reduced scores of the separate
parts.
Ryan et al cite 1981
Canadian statistics that there were 607,800 honey bee colonies in Canada. Relatively few of these colonies are
overwintered, most of them being destroyed after the honey harvest each year
(for example, 123,000 of the 160,000 colonies in Alberta in 1980 were not
overwintered). In combining their data
on adult bees with those of Hocking and Matsumura (1960) on bee brood, Ryan et
al estimate harvest values of 3.6 kg fresh bees and brood per colony. At 607,800 colonies in Canada in 1980, they
estimate that the potentially harvestable production of bees and brood amounted
to a maximum of 2.2 x 106 kg fresh weight.
In tests involving rat
feeding trials, Ozimek et al (1985) studied the nutritive value
of protein obtained after alkaline extraction from whole adult honey bees. Whole dried honey bees contained 56.8% crude
protein (N x 6.25) and 11.1% chitin or 52.0% when corrected for the nonprotein
N in the chitin; the protein concentrate contained 64.2% crude protein and no
chitin. Corrected for non-protein
N in chitin, the apparent protein digestibility of whole dried bees increased
from 62.1% to 68.5% and the true digestibility from 71.5% to 79.8%. The true digestibility in the concentrate
was 94.3%. In addition to the increased
digestiblity, the protein quality of the concentrate was higher than that of
whole dried bees as measured by amino acid availabilities (Table 4; see
authors' Tables 2 and 4), PER (protein efficiency ratio), and NPU (net protein
utilization), as well as by an increased content of some of the amino
acids. According to the authors, the
absence of chitin in the protein concentrate is probably the major reason for
its superior quality compared to that of whole dried bees, as chitin is
indigestible and of no nutritional value to monogastric animals (see Lovell et
al 1968).
Ozimek et al also
calculated the chemical score of the whole dried honey bees and the protein
concentrate in relation to the amino acid content in egg protein (see Block and
Mitchell 1946; FAO 1970, in Chapter ?) and also a "relative chemical
score" which takes into account the availability of the individual amino
acids and is therefore a more accurate prediction of protein quality (Table 5;
see authors' Table 5).
Thoenes and Schmidt (1990) were
able to collect 100 g of larvae/10 min. by using a 500 ml plastic
laboratory wash bottle to
"wash" the cells with a thin stream of water. Larvae of all sizes readily wash from the
cells, less than 1% were damaged and the method can be used in the field as
well as the laboratory. It would be
necessary to uncap cells to obtain mature larvae and pupae. The method is presumably effective for
removing drone larvae although the authors do not so state.
Lepidoptera
Landry et al (1986)
provided proximate and amino acid analyses on larvae of six species in three
families: Family Noctuidae included the armyworm, Pseudaletia unipuncta
(Haworth), the southern armyworm, Spodoptera eridania (Cramer), and the
fall armyworm, Spodoptera frugiperda (J.E. Smith); Family Saturniidae
included Callosamia promethea (Drury) and Hyalophora cecropia
(L.); and the Family Sphingidae included Manduca sexta (L.). The noctuid larvae ranged between 54% and
58% crude protein on a dry weight basis (Table 6; see authors' Table 1). The fat, and thus energy content was higher
in the larvae than in conventional protein supplements. The extremely high fat
content in S. frugiperda, however, which were fed on an artifical diet,
probably reflects the diet and the fact that not all larvae were able to clear
the gut before they were harvested. In
the saturniids, crude protein was 49.4% in C. promethea and 54.7% in H.
cecropia. Fat content was similar to that found in fish and meat
supplements. The sphingid, M. sexta,
contained 58% crude protein and a very high fat content whether reared on
artificial diet or on fresh plant material.
Amino acid analyses of
the larvae indicated them to be marginal or somewhat low in methionine-cysteine
and arginine, especially when reared on fresh plant material as opposed to
artificial diet. In chick feeding trials to 18 and 21 days of age, involving
the saturniid and sphingid larvae in practical diets, there were no significant
differences in weight gain or feed/gain ratio in chicks fed the corn-caterpillar
diets compared to chicks fed a corn-soybean control diet.
In an article
entitled, "Grizzlies come back. By relearning old behavior, the great
bears may yet avoid extinction," author Daniel Glick (1992)
describes studies by Steven and Marilynn French showing that cutworm moths are
an important food of grizzly bears in the Absaroka Mountains east of
Yellowstone National Park in Wyoming.
The Frenches observed bears (Ursus arctos horribilis),
more than 100 totally, feeding on the moths above timberline. In a study on bear feeding ecology in
Glacier National Park, Montana, White and Kendall (1993) found
nine moth aggregation sites in the alpine regions of the park. Moths identified from two of the study sites
all proved to be Euxoa auxiliaris Grote (Noctuidae). Moths collected in mid-July 1992 averaged
24.4% protein and 34.4% fat; mid-August collections averaged 18% protein and
35.4% fat. Bear use of moth aggregation
sites lasted at least from July 12 to September 3 in 1992, and 67% of bear
activity on the talus slopes was directed toward moth feeding. All bears were grizzlies, no black bears
were observed. Several species of birds
also fed on the moths.
The moth has an
interesting life cycle. It undergoes
its development in the Great Plains where the eggs, about 2000 per female, are
laid in the soil in the fall. The
larva, which has a total of seven instars, is in the first or second instar
when it enters diapause. It resumes
feeding in the spring on plants such as alfalfa or small grains. The larval period varies depending on
temperature and location but may be as long as 25-32 days in Kansas and 43-63
days in Montana. Pupation is in
underground cells. The adult moths
emerge in early summer and migrate westward into the Rocky Mountains where they
congregate above timberline. The moths
occupy the interstitia of talus slopes during the day and feed nocturnally on
nectar from alpine and subalpine flowers.
The return migration to the plains occurs in the late summer or early
fall. White and Kendall mention several
areas in the Rocky Mountains of Wyoming and Montana where grizzlies are known
to feed on cutworm moths and other alpine insect aggregations. In the Mission Mountains, grizzlies feed not
only on E. auxiliaris, but also on ladybird beetles (Coccinella and
Hippodamia spp.).
Orthoptera
Glover (1875, pp.
138-140) suggested that some way should be found for using the
devastating hordes of western grasshoppers (Family Acrididae) as a substitute
for manure or drying them as feed for hogs and fowl. He states that turkeys, ducks and other fowl are useful in
destroying them, and "a large flock of turkeys will soon clear a field of
these pests." Also described are
"hopperdozers" and various specialised nets for harvesting
grasshoppers.
Packard (1878, p. 441)
described how the African locust (Acrididae) is used as bait for the sardine
fishery (see under Algeria), and suggested that should a similar need for bait
arise on the Atlantic or Pacific coasts of the United States, large quantities
of fish-bait could be prepared by western farmers in locust years.
Whitney (1892; vide
Wakeland 1959, p. 42) wrote, relative to the preying of gulls on the Mormon
cricket, Anabrus simplex (Haldeman) (Family Tettigoniidae), and
particularly the deliverance of the early Mormon pioneers in the Salt Lake
Valley in 1848:
They were saved, they believed, by a
miracle . . . Just in the midst of the work of destruction, great flocks of
gulls appeared, filling the air with their white wings and plaintive cries, and
settled down on the half-ruined fields.
At first it seemed as if they came but to destroy what the crickets had
left. But their real purpose was soon
apparent. They came to prey upon the
destroyers. All day long they gorged
themselves, and when full, disgorged and feasted again . . . until the pests
were vanquished and the people were saved.
The heaven-sent birds then returned to the lake islands whence
they came, leaving the grateful people to shed tears of joy at the wonderful
and timely deliverance wrought out for them.
Several other early authors have mentioned the gorging, disgorging, and
regorging of gulls upon Mormon crickets.
Walton (1916, pp.
14-15) described two kinds of hopperdozers. McHargue (1917)
stated that with suitable equipment for harvesting grasshoppers, they might
afford a new high-protein source for swine, poultry, and other livestock
rations. He conducted a proximate
analysis on dried Melanoplus spp. (Acrididae) showing 75.3% protein,
7.21% fat, and 5.61% ash. Amino acid
analysis showed the grasshoppers to be high in lysine compared to other
sources. Minerals were also analyzed.
Milby and Penquite (1940),
working in Oklahoma, note that turkey growers have followed the practice of
allowing young birds to range for most of their food, with only a feeding of
grain at night to induce them to come home to roost. Losses are sometimes high with this system, but according to
Milby and Penquite, "good turkeys" are produced. Their food is largely insects and tender
green feed. Where grasshoppers are
numerous, farmers have used the young turkeys to reduce numbers of the pests
and at the same time make a profit on the turkeys. The authors mention that, on the other hand, those concerned with
marketing have discouraged this method of management, claiming that it produces
"tough, stringy birds with an undesirable flavor when cooked."
In feeding trials
conducted by Milby and Penquite, 12-week-old poults were fed the
experimental rations for five weeks, containing dried grasshoppers either
cooked or not cooked, or frozen grasshoppers.
Most of the grasshoppers were immature stages, with Melanoplus
differentialis comprising more than 60% of the samples, and smaller
percentages of M. mexicanus, M. packardii, M. femur-rubrum, M.
bivittatus, and unidentified species.
The mixed sample contained: protein 62.8%, fat 18.4%, ash 3.9%, fiber
10.9%, and N.F.E. 4.0%. No significant
reduction in growth resulted from feeding the rations containing grasshopper
meal, but poults fed grasshoppers required more feed per pound of gain
(significance not determined). In
flavor tests, two birds on the control diet were judged to be the best, but
there were no undesirable flavors or odors in any of the birds.
Wickware (1945)
reported deaths among turkeys from eating grasshoppers in November near Ottawa,
Canada. A moribund turkey, upon
autopsy, was found to have the crop distended and full of grasshoppers which
proved to be Melanoplus femur-rubrum
(Deg.) and M. mexicanus Sauss., two species very common in the area.
Wickware quotes personal communication from H.L. Seamans of the Division of
Entomology, part of which was as follows:
It has been my experience both in
Alberta and Montana that gallinaceous birds may be killed by the grasshoppers
themselves, particularly where they are eaten in abundance without any
appreciable amount of other food being taken at the same time. This occurs most frequently in the autumn
when grasshoppers are sluggish and easily picked up by the birds without any
intervening exercise. In the summer,
when the grasshoppers are active and the birds have to work to catch them, they
are picking up other food between times and do not get their crops filled with
just grasshoppers.
I know that in Montana where farmers
collected grasshoppers by the bushel and dried them for winter poultry feed,
they had to be very careful to make sure that the feed mixture did not contain
too high a percentage of grasshoppers.
When this was not observed, turkeys and chickens died quite readily.
Death is apparently caused by the
hard parts of the grasshopper, particularly the heavily spined legs, not only
irritating but actually puncturing the crop.
Some cases were autopsied where severe hemorrhage had occurred in the
crop, and always the crop was severely inflamed. There were some cases where the intestine was punctured by
grasshopper legs. These conditions were
also produced experimentally where poultry were fed for a few days on nothing
but grasshoppers.
Non-gallinaceous birds are
apparently not affected in any way by feeding an over-abundance of
grasshoppers. Ducks and geese seem to
be able to eat unlimited quantities with no ill effects. Small song birds frequently feed on grasshoppers
almost exclusively but they always clip off the wings and legs before swallowing
the insect.
From the above and
other research cited, Wickware recommends the feeding of a liberal quantity of
mash in the morning during the late fall months to reduce and dilute the
results of foraging.
Wakeland (1959, p.
43) states that hawks feast upon Mormon crickets and that, "Supervisors
commonly follow an unusual assemblage of hawks to guide them to
infestations." Many other species
of birds and mammals are fond of the crickets, including coyotes, skunks,
badgers and rodents, as well as lizards and horned toads (pp. 44-46).
Poultry, hogs and dogs also eat them.
In studies on Mormon
crickets, A. simplex, collected in Colorado (DeFoliart et al 1982),
proximate analysis revealed a crude protein content of 58% on a dry weight
basis (Table 7; see authors' Table 2). Amino acid analysis of crickets
indicated that for broiler chicks, methionine, arginine, and tryptphan in that
order would be the limiting amino acids (Table 8; see authors' Table 3). In feeding trials, however, practical corn-cricket-based
diets produced significantly better growth of chicks to 3 weeks of age than was
produced by a conventional corn-soybean-based diet (Table 9; see
authors' Table 5). Diet #1 in Table 3
is the corn-soy control, Diets #2 and #3 the corn-cricket diets. Diets 1 and 3 were supplemented with amino
acids to bring them up to the levels recommended by the NAS-NRC (1977),
and all of the diets were supplemented up to recommended levels for minerals
and vitamins, since there were no data on these for Mormon crickets. This supplementation with minerals and
vitamins ensured that any differences in growth were dependent on the protein
quality of the diet. As shown in Table
9, supplementation of corn-cricket diet #3 with purified amino acids did
not significantly increase the weight of chicks feeding on that diet over those
on the unsupplemented corn-cricket diet (#2). Some of the difference between Diets 2 and 3 over #1 may have
been due to the higher metabolizable energy content of the corn-cricket
diets because of the high fat content of the crickets.
DeFoliart et al
determined dry weights of cricket life stages over a 3-year period and
found that male weights averaged between 0.71 and 0.95 g during each of the 3
years, while female weights averaged between 1.17 and 1.50 g. The mean dry weight for both sexes combined
in 1980 was 1.09 g. Cricket densities of 10-20/m2 are not
uncommon, and at those densities, and with an average dry weight per cricket of
1.09 g, a 1 km2 band totals 11-22 metric tons of high-protein
powder. Based on 1981 prices of corn
and soybean meal, it was estimated that the wholesale value of crickets in a 1
km2 band ranged from $3,300 to $6,600.
The above authors
(DeFoliart et al) raised several questions relative to possible commercial exploitation
of the Mormon cricket as animal feed.
First, an unanswered question is whether management practices could be
developed that would tend to ensure a reasonably dependable cricket crop, a
factor that would be important in gaining access to the market. Secondly, the efficiency of cricket
utilization of rangeland vegetation in relation to, or in comparison with,
other rangeland livestock production systems would be important. Relative to this, Cowan and Shipman (1947)
had quoted unpublished studies by R.B. Swain showing that cricket food
preferences placed them in direct competition with cattle in northern Nevada
and other areas where the northern desert shrub type of vegetation prevailed.
On the other hand, there was little damage to forage, even in outbreak years,
in the grassland types of range in Montana, Wyoming and eastern Idaho.
According to Ueckert and Hanson (1970), in the arid ponderosa
pine-bunchgrass community in northern Colorado, crickets were primarily
herbivorous but also carnivorous and fungivorous, with forbs contributing about
50% of the diet, arthropods and fungi about 37%, and grasses, clubnoss, and
grass-like plants about 13%.
In a follow-up
on the study by DeFoliart et al, Finke et al (1985) used Mormon
crickets in purified diets (Table 10; see authors' Table 2) and found that
methionine and arginine are colimiting.
Adding either methionine or arginine alone did not significantly improve
either final weight or feed/gain ratio.
In an 8-week chick feeding trial (Fig. 2; see authors' Fig. 1),
however, in which Mormon crickets were incorporated into practical diets
replacing soybean meal as the major protein source, there were no significant
differences in weight gain or feed/gain ratio in the corn-cricket diet
compared to the corn-soy control.
Final body weights averaged 2095 g on the corn-soybean meal diet,
and 1947 g on the corn-cricket diet which were not significantly
different.
Nakagaki et al (1987)
provided proximate, amino acids, and minerals analyses of the house cricket, Acheta
domesticus L. (Family Gryllidae).
Crude protein content was 62.0% on a dry weight basis (5.2% water). The data on Acheta are quite similar
to those obtained on the tettigoniid, A. simplex, amino acid analysis
indicating that methionine and arginine would be the lst-limiting amino
acids, followed by tryptophan. In chick trials to 3 weeks of age using
semipurified diets, however, final weights of chicks fed the experimental diets
were not significantly different.
Feed/gain ratios indicated, however, that tryptophan may be
limiting. In experiments using
practical corn-cricket diets to 2 weeks of age, again the addition of
methionine and arginine resulted in no significant differences in final
weights. There was a significant
improvement in feed/gain ratios, however, when both were added (but not when
either was added alone). That these
amino acids are colimiting is similar to the findings of Finke et al (1985) on
the Mormon cricket.
Finke et al (1987)
reported the results of experiments in which weanling rats were fed diets
containing corn gluten meal (CGM), Mormon cricket (Anabrus simplex
Haldeman) meal (MCM), MCM supplemented with methionine (MCM + Met) or CGM-MCM
mixtures as the sole source of dietary protein in purified diets. Animal response (weight or nitrogen gain)
was analyzed as a function of nitrogen intake and described by a series of
curves using a four-parameter logistic model (described separately by Finke et
al). When used for maximum nitrogen retention,
the protein sources ranked as follows: MCM + Met > 40 CGM-60 MCM > 50
CGM-50 MCM > 60 CGM-40 MCM > MCM > CGM. When used for maximum weight gain, the ranking was: MCM + Met
> 40 CGM-60 MCM > 50 CGM-50 MCM = 60 CGM-40 MCM > MCM > CGM. The rankings of the protein sources when
used for weight maintenance or nitrogen equilibrium were similar to those seen
for maximum weight or nitrogen gain except that the ranking of MCM changed from
fifth to first. The investigators concluded from the results that MCM is a good
quality protein source and that methionine is the first limiting amino acid
when used for growth but not for maintenance.
Finke et al (1989)
evaluated the protein quality of three insect sources, Mormon cricket (Anabrus
simplex) meal (MCM), house cricket (Acheta domesticus) meal (HCM)
and eastern tent caterpillar (Malacosoma americanum) meal (TCM) relative
to that of lactalbumen (LA) and soy protein (SP), using both amino acid
analysis and a rat bioassay. The amino
acid pattern of the three insect meals indicated that methionine should be the
first limiting amino acid for growing rats.
In the rat bioassay, weanling rats were fed graded levels of the five
proteins in purified diets and the response (weight or nitrogen gain) evaluated
as a function of nitrogen intake. When
used either for weight maintenance, nitrogen equilibrium, maximum weight gain
or maximum nitrogen retention, the five protein sources could be ranked in the
following order: LA>HCM>MCM=SP>TCM.
Relative to lactalbumin, the value of all four protein sources decreased
with increasing nitrogen intake. The
results indicate that some insect proteins are equivalent or superior to soy
protein as a source of amino acids for growing rats. The authors suggest that the low values for TCM may have been
related to factors other than protein quality.
Nakagaki and DeFoliart (1991)
estimated the food conversion efficiency of the cricket, Acheta domesticus,
when kept at temperatures of 30°C or higher and fed the high-quality diets used to bring
conventional livestock to market condition, to be about twice as high as those
of broiler chicks and pigs, 4 times higher than sheep and nearly 6 times higher
than steers when losses due to dressing percentage and carcass trim were taken
into account. High fecundity increases
the advantage in favor of the insect.
Female crickets lay an average of 1200 to 1500 eggs over a period of 3-4
weeks. By comparison, in beef production four animals exist in the breeding
herd per market animal produced, thus giving crickets a true food conversion efficiency
some 20 times better than for beef.
Parajulee et al (1993)
developed a model that simulates the harvest of a pre-determined number of eggs
of the house cricket, Acheta domesticus (L.) per day by regulating the
numbers and ages of adults in the breeding colony. This research was done relative to a mass-rearing system for
crickets as food which was being developed at the time by the authors. The system was designed to harvest 6,000
crickets per day, but is expandable depending on the daily production
desired. Previously, it had been
difficult to seed rearing cages with the proper number of eggs per day without
the time-consuming work of daily sorting and counting of thousands of eggs from
the oviposition medium.
Insects
as Food of Non-human Primates
Suzuki (1966)
described insect eating, primarily ants and termites, by wild chimpanzees (Pan
troglodytes) in Tanzania, and cites other studies on the eating of insects
by chimpanzees, Japanese monkeys (Macaca fuscata) and baboons (Papio
anubis). Chimpanzees and the monkeys are largely vegetarian. Also cited is an earlier study by Shaller
who reported that gorillas (Gorilla gorilla) never feed on insects. Suzuki, as had Jane Goodall earlier,
observed chimpanzees "fishing" for termite soldiers. The tools used
for inserting into the termite holes were about 45 cm long and made from either
Hibiscus calyphyllus (Malvaceae) or Acalypha ornata
(Euphorbiaceae). Relative to the former, Suzuki states: "This tree is a
kind of small shrub with soft, strong fibrous bark. The chimpanzees stripped the bark from a twig of this tree and
made the tool from it. The bark
possesses the proper strength as a tool and yet is relatively soft so that
termites can easily bite into it. It
seems apparent that the chimpanzees selected this effective
material." It should be noted that
termite fishing is also a practice among indigenous human populations in
Africa.
Experimental work by Cornelius
et al (1976) demonstrated that chitinolytic enzymes from the gastric
mucosa of the primate, Perodicticus potto, are true chitinases,
suggesting that some other vertebrates also secrete a true chitinase.
Carpenter (1921),
using a captive young monkey, undertook a study in Uganda to determine the
effect of aposematic (warning) coloration or behavior on the acceptibility and
edibility of insects. Insects were
presented individually to the monkey, or, in some cases, the monkey was leashed
and taken on walks. Carpenter appears
to have become quite attached to the monkey (who is designated as M in the
daily experiment write-ups), describing him as a "delightful youngster of
the abundant grey species of Cercopithecus, with a whitish band over the
eyes." After determining the range
of responses to proffered insects from very tasteful to very distasteful,
Carpenter adds, "I may say that the monkey's facial expression
gives a very accurate indication of whether or not the insect is tasty. Carpenter then relates:
Once I offered the monkey my closed
hand. He came up to see what was
inside, and I opened my hand and showed him a beetle which previous experiment
had proved to be very distasteful. The
monkey literally broke into a broad grin and walked away, evidently taking it
as a joke!
The non-aposematic
grasshoppers were definitely among the most consistently relished of the
insects proffered by Carpenter. He remarks: "The species of monkey used
for these experiments eats great numbers of Acrididae; I have often seen them
hunting through long grass in the evenings, catching the grasshoppers which
rose in front of them." He also
mentions that a tettigoniid (katydid), Conocephaloides mandibularis
Charp., which is esteemed as food by the Baganda of Uganda, "was always
found extremely edible by my monkey on L. Victoria, who would eat them until
his overfilled stomach rejected them!"
Insects
as Food for Zoo Animals
Mealworms, both small
(Tenebrio molitor) and large (Xophobas morio), waxworms (Galleria
mellonella) and crickets (Acheta domesticus) are the insects most
commonly fed in zoos and aquaria. In
chemical composition studies (Pennino et al 1991), percent water, and
total N (N x 6.25 = crude protein), crude fat and ash as a percentage of dry
matter varied widely. Values for crickets were, respectively: 73%, 10.3%, 19.9%
and 4.2%; for small mealworms: 61.2%,7.8%, 23% and 2.5%; for large mealworms:
55.6%, 7%, 44.9% and 8.6%; and for waxworms: 59.7% 5.5%, 56%, and 3.2%. Acid detergent-nitrogen (ADF-N) was
determined as a measure of unavailable N (about 7% of total N), and neutral
detergent fibre (NDF) as an estimate of chitin (averaged about 20% of dry
matter). From these data, the authors
discuss true protein values and the nutritional importance of chitin both in
animals with, and those without, chitinase activity.
Retinol and a-tocopherol
content are direct measures of vitamin A and vitamin E activity, respectively
(two of the fat soluble vitamins).
Pennino et al found that the two marine invertebrates tested, krill and
squid, were high in retinol, but concentrations in insects were <2.0 ug/g
dry matter, indicating that insects in general may be a poor source of vitamin
A. Of the insects analyzed, only honey
bees may provide adequate vitamin A levels without need for supplementation. Squid were highest in a-tocopherol,
with insects ranging from 10.4 ug/g dry matter in male honey bees to 179.3 in
cockroaches. Health problems from
vitamin E deficiency have not been specifically documented in insectivores, and
the authors conclude that levels provided by invertebrate prey in general meet
dietary requirements. In a short-term
feeding trial (one week) involving crickets and large mealworms, it was
demonstrated that the vitamin E content of invertebrates used as feed can be
altered by altering the dietary levels of this nutrient (significant only for
mealworms). Nutrient data were also obtained in this study on several species
of insects and other invertebrates (both wild and commercially obtained) which
are not mentioned above.
Dierenfeld (1993)
points out that insects are a substantial part of, or the entire diet fed to
numerous species of amphibians, reptiles, birds and mammals in zoological
parks, and she provides an excellent discussion of the specific quantity,
quality and adequacy of insect-suppled fat, protein, carbohydrate, vitamins and
minerals in meeting the different dietary needs. Dierenfeld et al (1995) reported that retinol and
carotenoid analysis of 10 invertebrates commonly fed in zoos demonstrated low
concentrations of vitamin A activity. A
variety of carotenoids found particularly in free-ranging invertebrates
consuming natural diets implies that insectivores may rely on carotenoid
pigments as vitamin A precursors. The
investigators obtained clinical and histological data suggesting that
specialist insectivores may have low dietary requirements of vitamin A.
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Chapter 10 of
The Human Use of Insects as a Food Resource: A Bibliographic Account in
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21: pages?