Production of earthworms as a potentially economical source of protein

The main objectives of this study were (1) to determine the optimum frequency for transferring a fixed population of Eisenia foetida into fresh surroundings to effect maximum production of earthworm biomass, (2) to determine carrying capacity and maximum production of E. foetida biomass per unit area–volume–time at 24°C, and (3) to measure the nucleic acid concentration of this earthworm. Population were rapidly decimated in limed peat moss with horse manure as food when transferred weekly or when held for ten weeks in the same substrate; no significant differences and high survival obtained at intermediate intervals. Significantly more cocoons were produced when transfers were made every two weeks, and a trend was seen toward a lower level of cocoon production with length of detention in substrate. The growth rate of adults was approximately similar in relation to the frequency of transfer, as was biomass, at transfer frequencies of every 2 to 9 weeks. One interpretation of the data is that a detention interval of 6 to 8 weeks is optimum for maximizing production of biomass; eight weeks is the interval commonly selected in commercial practices. Carrying was 9.5 g live weight on a surface area–volume of 24 cm²–110 cm³ with horse manure as food on 20 g of soil as substrate; maximum production in this space was 2 g live weight in 7 weeks, which extrapolates to 6685 kg protein/ha yr. Nucleic acid concentration was 2.9%, which falls below values of about 6–28% obtained for microbes, and may exceed values for mammalian muscle by about twofold.