NUTRITIONAL ASPECTS OF INSECTS AS FOOD

[Philsuma]

The tables are 'skewed' and hard to read, but the other information is very helpful IMO.


NUTRITIONAL ASPECTS OF INSECTS AS FOOD

am Authors Reviewer

Joni B. Bernard, PhD Mary E. Allen, PhD Duane E. Ullrey, PhD

Department of Zoology National Zoological Park Department of Animal Science
Michigan State University Smithsonian Institution Michigan State University
East Lansing, MI 48824 Washington, DC 20008 East Lansing, MI 48824

Insectivory is a term that is sometimes used to refer to the consumption of a wide variety of invertebrate
species, including arachnids, annelids and crustaceans, as well as insects. Information in this document
is restricted to insects and annelids. Many captive animals will consume invertebrates, live or dead, but
it is often necessary to offer live invertebrates (primarily insects) to a variety of fishes, amphibians,
reptiles, birds and small mammals. For obligate insectivores, live invertebrates may serve as the primary
dietary item. For most species, however, live insects and other invertebrates offer opportunities for
behavioral enrichment and can prolong time spent feeding.

To successfully manage captive insectivorous species, data on nutritional composition of
invertebrate prey are especially important. Since live insects may be the only food offered to some
species, nutritional deficiencies can quickly arise if the nutrient levels in the live prey are imbalanced.
Unfortunately, the few commercially available invertebrates are an incomplete nutrient package without
appropriate supplementation, and may adversely affect the dietary husbandry of species which consume
them as a substantial portion of the their total diet.

Typical laboratory analyses of invertebrates commonly fed in zoos are provided in Tables 1 and
2. Scientific names of these invertebrates are shown in Table 3, and the methods of analysis are
summarized in Table 4. Protein concentrations in invertebrate species are relatively high, ranging from
40-70% on a dry matter basis (DMB). Estimates of protein concentration are commonly based on
organic nitrogen content multiplied by 6.25 (which assumes protein is 16% nitrogen). However, many
invertebrates contain substantial quantities of non-protein nitrogen, from sources such as chitin, which
2
may artificially elevate available protein estimates. Chitin, an integral part of the invertebrate cuticle
(exoskeleton), can be estimated by determining the acid detergent fiber fraction corrected for ash.
Since chitin contains about 7% nitrogen, each 1% of ADF (presumed to be chitin) contains the
equivalent of 0.4% crude protein (1 x 0.07 x 6.25). It has been reported, that some insectivores have
an intestinal chitinase, while others may rely on chitinases produced by gut microorganisms. Chitin
digestibility in three species of mammals has been shown to range from 2-20%. However, there is no
evidence that the nitrogen released can contribute to the protein available for absorption by the
insectivore.

Ether extract, an estimate of fat, is highly variable among invertebrate species, ranging from 4-
55% (DMB), and may vary substantially within a species depending on developmental stage. Many
insects accumulate fat during larval development, and two of the most commonly utilized insects in zoos
are larval forms, mealworm larvae and wax moth larvae. If these larvae constitute a substantial part of
the diet, they may present a disproportionately high fat content, leading to excess energy (caloric) intake
relative to other essential nutrients.
Annelids, such as earthworms and night crawlers, are readily available prey items. Generally,
these species have less than 20% ether extract (DMB), and contain ample calcium and appropriate
calcium to phosphorus ratios (1.5:1 to 2:1). The nutrient composition of annelids is likely to be variable,
however, depending on the composition of the substrate (e.g., soil) on which they are grown and/or
maintained.

The primary problem in nutrient composition of most insects fed in captivity is that they are poor
sources of calcium. The practice of dusting or dipping insects in calcium supplements, even if the insects
have been sprayed with cooking spray (said to improve adhesion of supplements), generally provides
inconsistent or inadequate levels of calcium and may adversely affect the palatability of the insects.
Additionally, if the insects are not consumed immediately, self-grooming or other activity may
significantly reduce or eliminate the supplement.

The practice of supplementing crickets with a high calcium diet has been established at many
zoos, and the benefits have been documented.1 An example formulation is shown in Table 5.
Commercially manufactured high calcium cricket diets are currently available from the following sources:
Marion Zoological, Plymouth, MN 55441, 800-327-7974; Purina Mills, St. Louis, MO 63116, 314-
768-4592; Zeigler Bros., Gardners, PA 17324, 800-841-6800. Critical considerations in the use of
high calcium diets for crickets are: thorough mixing of feed after shipment and before feeding (minerals
may separate), continuous provision of fresh water with no other foods, and maintenance of insects at
around 27°C with access to the diet for at least 2-5 days, and no longer than 7-8 days.
Pinhead or subadult crickets, contrary to some reports, are also limited in calcium content (see
Table 2). Because pinheads are smaller in size than adult crickets, they may be a more appropriate
food choice in some situations. However, they too must be supplemented with calcium. The high
calcium cricket diets may be used for pinheads following the same general directions; however, it
appears that the diet must be ground extra-fine to accommodate the small mouth parts of emergent
crickets.

Researchers have also described dietary methods of increasing the calcium content of
mealworm larvae and wax moth larvae. The calcium content and calcium-phosphorus ratio of
mealworm larvae were improved by feeding vitamin/mineral supplements.3 However, similar results
may be obtained with more readily applied methods. Feeding mealworm larvae commercially available
3
high calcium cricket diets appears to result in improved calcium content and calcium-phosphorus ratios
(see Table 2). The mealworm larvae should be handled in a manner similar to crickets fed the same
high calcium diet.

Wax moth larvae also may serve as a source of live food for animals in captivity. Methods for
improving their calcium content and calcium-phosphorus ratio have been described.2 A mixture of
honey (12 ml), high protein baby cereal (21.3 g), calcium carbonate (5.7 g), glycerol (10 ml), and
water (4 ml) may be prepared. The container in which the diet and wax moth larvae are kept should
provide for air circulation. Glass jars with cheese cloth tops and plastic cottage cheese-type containers
with air holes punched in the top, in addition to a number of other creative containers, have been used
successfully. Although not mentioned in the original publication, the mixture should occasionally (on
alternate days) be agitated to prevent caking of the larvae in the diet.

High calcium diets fed to insects intended as prey items are not designed to meet the nutrient
requirements of the insect. These diets are intended to fill the insect’s gastrointestinal tract and provide
a more complete nutrient package for the insectivorous animal consuming the insect. Rotating insects
onto the high calcium diet and feeding them out on a regular basis is critical. Extended consumption of
high calcium diets (particularly by crickets and mealworm larvae) may lead to high insect mortality.
Insectivorous animals in the wild likely consume a wide variety of invertebrate species. In
captivity, we can only reliably provide a limited number of invertebrate species, few of which are good
nutrient packages by themselves. Therefore, we have a responsibility to administer a feeding program
with supplements that compensate for known shortcomings in the nutrient composition of the
invertebrates that are available to us.

Literature Cited
1 Allen, M.E. and O.T. Oftedal. 1989. Dietary manipulation of the calcium content of feed crickets. J. Zoo. Wildl.
Med. 20:26-33.
2 Strzelewicz, M.A., D.E. Ullrey, S.F. Schafer, and J.P. Bacon. 1985. Feeding insectivores: increasing the calcium
content of wax moth (Galleria mellonella) larvae. J. Zoo. An. Med. 16:25-27.
3 Zwart, P. and J. Rulkens. 1979. Improving the calcium content of mealworms. Int. Zoo. Yearb. 19:254-255.
4

Table 1. Proximate analysis, fiber fraction and energy content of invertebrates (DMB). abc
Item DM CP EE ASH ADF GE
--------------------------------%----------------------------- kcal/g
Black worm 18.4 47.8 20.1 4.5 0.7 5.57
Blood worm 9.9 52.8 9.7 11.3 * *
Cockroach, American 38.7 53.9 28.4 3.3 9.4 6.07
Corn borer larvae, European 27.3 60.4 17.2 2.9 13.1 5.69
Corn borer pupae, European 28.0 64.2 17.0 2.6 15.4 5.60
Cricket, domestic, adult 31.0 64.9 13.8 5.7 9.4 5.34
Cricket, domestic, adult, hi-Ca diet 30.3 65.2 12.6 9.8 13.2 5.40
Cricket, domestic, pinhead d 47.4 * * * * *
Earthworm 20.0 62.2 17.7 5.0 9.0 4.65
Fish fly 26.5 63.9 19.5 5.8 10.9 5.88
Fruit fly 29.6 70.1 12.6 4.5 27.0 5.12
Fruit fly larvae 21.2 40.3 29.4 9.8 5.9 5.57
Fruit fly pupae 32.4 52.1 10.5 14.1 17.4 4.84
House fly larvae, dry 93.7 56.8 20.0 6.8 18.0 6.07
House fly pupae, dry 96.4 58.3 15.8 6.8 19.9 5.70
Mealworm beetle 38.6 63.7 18.4 3.1 16.1 5.79
Mealworm larvae 37.6 52.7 32.8 3.2 5.7 6.49
Mealworm pupae 39.0 54.6 30.8 3.4 5.1 6.43
Mealworm larvae, king 40.9 45.3 55.1 2.9 7.2 7.08
Mealworm larvae, king, hi-Ca diet 42.2 38.9 45.4 3.5 7.7 6.79
Mosquito larvae, dry 94.0 42.2 16.1 11.8 * *
Night crawler 16.3 60.7 4.4 11.4 15.0 4.93
Tubifex worm 11.8 46.1 15.1 6.9 * *
Water flea, dry 91.7 55.2 6.6 10.8 * *
Wax moth larvae 34.1 42.4 46.4 2.7 4.8 7.06
Wax moth larvae, hi-Ca diet 39.9 * * 2.5 * *
a Data provided by Duane E. Ullrey, Comparative Nutrition Laboratory, Michigan State University, and
Mary E. Allen, National Zoological Park.
b Scientific names of invertebrates provided in Table 3.
c Abbreviations and methods of analysis described in Table 4.
d Analysis by Covance Laboratories, Inc., Madison, WI 83707; DM in vacuum oven (70°C).
* Value not determined.
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Table 2. Major and trace mineral content of invertebrates (DMB). abc
Item Ca P Mg Na K Cu Fe Zn Mn Se
------------------%------------------ ----------------ppm------------------
Black worm 0.11 0.85 0.09 0.28 0.98 10 1091 166 16 0.87
Blood worm 0.38 0.90 0.12 0.62 0.35 30 2940 115 22 0.37
Cockroach, American 0.20 0.50 0.08 0.27 0.87 14 90 57 5 0.36
Corn borer larvae, European 0.23 0.64 0.12 0.02 0.05 24 289 90 18 0.31
Corn borer pupae, European 0.22 0.67 0.13 0.02 0.05 20 269 98 16 0.20
Cricket, domestic 0.14 0.99 0.13 0.49 1.29 28 58 188 31 0.58
Cricket, domestic, hi-Ca diet 0.90 0.92 0.11 0.57 1.41 29 80 237 56 0.49
Cricket, domestic, pinhead d 0.22 1.27 0.14 0.43 1.62 14 200 268 33 *
Earthworm 1.72 0.90 0.14 0.02 0.06 18 4133 250 142 0.92
Fish fly 0.23 1.07 0.16 0.39 1.01 20 216 378 6 1.63
Fruit fly 0.10 1.05 0.08 0.42 1.06 18 138 171 39 0.07
Fruit fly larvae 0.59 2.30 1.89 0.09 1.28 16 235 176 110 0.49
Fruit fly pupae 0.77 2.73 2.41 0.12 1.66 25 1728 200 108 0.33
House fly larvae, dry 0.41 1.13 0.30 0.72 1.28 50 658 320 167 1.20
House fly pupae, dry 0.42 1.18 0.36 0.55 1.34 54 574 319 302 1.30
Mealworm beetle 0.07 0.78 0.19 0.16 0.92 22 77 113 10 0.29
Mealworm pupae 0.08 0.83 0.23 0.15 0.93 18 42 95 12 0.29
Mealworm larvae 0.11 0.77 0.22 0.14 0.91 19 43 100 14 0.31
Mealworm larvae, king 0.16 0.59 0.12 0.10 0.72 14 59 80 13 0.40
Mealworm larvae, king, hi-Ca diet 0.69 0.57 0.12 0.09 0.88 13 58 86 24 0.18
Mosquito, adult 0.82 1.24 0.33 * * 76 616 1057 70 *
Mosquito larvae, dry 0.79 1.07 0.21 0.39 0.52 57 3057 281 93 0.57
Night crawler 1.52 0.96 0.16 0.44 0.87 9 1945 1119 29 5.44
Tubifex worm 0.19 0.73 0.09 0.46 0.79 108 1702 190 30 2.16
Water flea, dry 0.10 1.17 0.16 0.98 0.99 39 3049 250 73 1.46
Wax moth larvae 0.11 0.62 0.11 0.05 0.72 9 22 76 3 0.66
Wax moth larvae, hi-Ca diet 0.50 0.33 * * * * * * * *
a Data provided by Duane E. Ullrey, Comparative Nutrition Laboratory, Michigan State University, and
Mary E. Allen, National Zoological Park.
b Scientific names of invertebrates provided in Table 3.
c Abbreviations and methods of analysis described in Table 4.
d Analysis by Covance Laboratories, Inc., Madison, WI 83707; Minerals by ICP emission spectrometry.
* Value not determined.
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Table 3. Scientific names of invertebrate species in Tables 1 and 2.
Common Name Genus species
Black worm Tubifex sp.
Blood worm Chironomus sp.
Cockroach, American Periplaneta americana
Corn borer, European Ostrinia nubilalis
Cricket, domestic Acheta domestica
Earthworm Allolobophora calignosa
Fish fly Chauliodes sp.
Fruit fly Drosophila melanogaster
House fly Musca domestica
Krill Euphausia sp.
Mealworm Tenebrio molitor
Mealworm, king Tenebrio sp.
Mosquito Aedes sp.
Night crawler Lumbricus terrestris
Tubifex worm Tubifex sp.
Water flea Daphnia sp.
Wax moth Galleria mellonella
Table 4. Nutrient abbreviations used in Tables 1 and 2, and methods of analysis.
Abbreviation Description Method of Analysis
Proximate analysis DM dry matter Freeze-dried & vacuum oven (60°C)
CP crude protein Nitrogen by Kjeldahl x 6.25
EE ether extract (crude fat) Extraction with diethyl ether
Ash total minerals Combustion overnight at 600°C
ADF acid detergent fiber Detergent digestion/extraction
GE gross energy Bomb calorimetry
Macro minerals Ca calcium Atomic absorption spectrophotometry
P phosphorus Light spectrophotometry
Mg magnesium Atomic absorption spectrophotometry
Na sodium Atomic emission spectrophotometry
K potassium Atomic emis sion spectrophotometry
Trace minerals Cu copper Atomic absorption spectrophotometry
Fe iron Atomic absorption spectrophotometry
Zn zinc Atomic absorption spectrophotometry
Mn manganese Atomic absorption spectrophotometry
Se selenium Fluorometry
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Table 5. Example of a high calcium (8%) diet formulated for crickets.
Ingredient Percentage by weight
Corn grain, ground 8.3
Alfalfa meal, dehydrated (17% CP) 10.0
Soybean meal, dehulled, solvent extracted (48% CP) 28.7
Wheat, ground 27.0
Calcium carbonate (38-40% Ca) 20.0
Dicalcium phosphate (21% Ca, 18% P) 2.0
Salt 0.5
Mineral premix a 0.25
Vitamin premix b 0.25
Soybean oil 3.0
a Contains per kg: 144g Ca; 0.04g P; 4.3g Mg; 0.6g K; 84.2g Fe; 83.3g Zn; 81.1g Cu; 119g Mn;
0.32g I; and 0.08g Se.
b Contains per kg: 28,000,000 IU vitamin A; 2,800,000 IU vitamin D3; 132,000 IU vitamin E;
0.6g vitamin K1; 7.1g thiamin; 2g riboflavin; 35.6g niacin; 9.5g D-pantothenic acid; 2g
pyridoxine; 1.5g folic acid; 99mg biotin; 6mg vitamin B12; and 190g choline.

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http://www.prairieexotics.ca/info/Nutri ... s_Food.pdf