Factors Affecting The Practical Mass-production And Harvest of Fly Larvae

Larde, G. 1989. Investigation on some factors affecting larval growth in a coffee-pulp bed. Biol. Wastes 30:11-19. Instituto Salvadoreno de Investigaciones del Cafe, Nueva San Salvador, El Salvador, C.A.

The author studied factors affecting the practical mass-production and harvest of fly larvae (as a protein source for domestic animals) developing in an open coffee-pulp (CP) bed, contained in a rectangular concrete tank 2.67 m long, 1.0 m wide and 0.51 m deep. The depth of the CP bed varied from 20 to 50 cm during the larval observation period of approximately 120 days. One-day-old CP was added periodically in amounts ranging from 4-13 kg wet matter per loading, the total weight loaded being 44.8 kg. Inoculation of eggs was by wild flies of the species Ornidia obesa (green hover fly), Hermetia illucens (soldier fly) and Musca domestica (house fly). Larvae migrating out of the tank dropped into a water-filled pit from which they were collecting for weighing.

An undesirable feature was the formation of an anaerobic zone that constituted 49% of the total volume of the CP bed. Larvae developed only in the aerobic zones extending about 12 cm deep from the top of the bed and 8 cm inward from the tank walls. Young fly larvae of all three species were found in the bed within the first week after initial loading. Larvae of M. domestica, which has the shortest life cycle, were pupating within a few days after the initial loading, and 815 larvae of this species migrated out of the bed on day 9. Heavy migrations from the bed occurred on days 36 and 50 after initial loading as the result of a heavy addition of coffee-pulp the preceding day in each case. These migrations presumably were caused by increased temperatures resulting from the heat generated by the rapid aerobic fermentation of the large volumes of substrate added. Such migrations did not occur when smaller lots of CP were added. The only rain, on day 82, also initiated a major migration. Turning of the CP, beginning on day 90, was expected to increase migrations, but that did not happen, probably because of the smaller numbers of larvae in the bed at that time.

Larvae of 0. obesa and H. illucens were found to tolerate temperatures from 22.50C to 35°C in the medium and the latter was found in zones up to 40°C. 0. obesa larvae were more migratory than H. illucens larvae, and this clearly contributed to the greater weight of the former that migrated out of the bed (11.8 kg wet matter or 0.3 kg wet matter kg1 wet matter total CP loaded, compared to 2.2 kg and 0.05kg, respectively, for H .illucens). The author recommends emphasis on harvest of these two species because the larvae are about 20 times heavier than M. domestica larvae. Some larvae of at least two of the species, H. illucens and M. domestica, were lost because of pupation within the medium, but there was apparently no attempt to determine the proportions lost in this manner.

The author states that under the management conditions of the experiment, it would not be possible to achieve a constant daily level of larval production. A mass recovery can probably be accomplished, however, within 3-5 weeks after the initial loading by flooding the bed or by heat. Also a better ventilation of the substrate

is needed to prevent formation of anaerobic zones. Data on minerals analyses of one-day-old CP and at 104 days and 145 days after initial loading are presented in tabular form.

Finke, M.D.; DeFoliart, G.R.; Benevenga, NJ. 1989. Use of a four-parameter logistic model to evaluate the quality of the protein from three insect species when fed to rats. J. Nutr. 119:864-871. Departments of Nutritional Sciences, Entomology, and Meat and Animal Science, University of Wisconsin, Madison, WI. 53706,

Author’s Abstract. The quality of three insect protein sources (Mormon cricket meal (MCM, house cricket meal (HCM and Eastern tent caterpillar meal (TCM was evaluated relative to that of lactalbumin (LA) and soy protein (SP) by 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 Sprague-Dawley 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. The individual nitrogen intake – animal response results could be described by a series of curves using a four parameter logistic model. The use of parameter sharing permitted the full range of responses to be described so that statistical differences between the dose-response curves could be identified. When used for either weight maintenance, nitrogen equilibrium, minimum 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 low values obtained for TCM may have been related to factors other than protein quality. The results of this study indicate that some insect proteins are equivalent or superior to soy protein as a source of amino acids for growing rats.