Effect of different organic substrates on reproductive biology, growth rate and offtake of the African night crawler earthworm (Eudrilus eugeniae)

There is limited knowledge about how organic substrates influence reproductive characteristics and growth of African night crawler earthworm (Eudrilus eugeniae). It is, however, essential to understand the reproductive characteristics, fecundity, longevity and growth patterns of earthworms to promote vermiculture biotechnology as a strategy for ecological livestock intensification and sustainable production of earthworm biomass as a source of protein and vermicompost. To generate this information, reproductive characteristics, growth and offtake of E. eugeniae were studied using four organic substrates including abattoir waste (AW), cattle manure (CM), soya bean crop residue (SBCR) and a binary mixture of cattle manure and soya bean crop residue (CM + SBCR) aged for 2 weeks. Growth rate was 17.7, 15.8, 15.6 and 14.3 mg/worm/day when earthworms were fed AW, CM + SBCR, CM and SBCR, respectively. Irrespective of the substrate, length and biomass of earthworms increased at a decreasing rate between the 1st and 11th weeks. Clitellum appearance was initiated at 31.5 ± 2.4, 32.8 ± 3.2, 33.7 ± 3.3 and 35.5 ± 2.4 days for AW, CM, CM + SBCR and SBCR, respectively, while cocoon initiation was at 69.0 ± 1.4 (AW), 54.9 ± 2.3 (CM), 51.7 ± 1.7 (CM + SBCR) and 60.0 ± 2.4 (SBCR) days. Cocoon production rate (0.41 cocoons/worm/day) was highest (P < 0.05) in earthworms fed CM + SBCR but abnormally lowest for AW. Cocoon incubation period ranged between 9 and 16 days for CM but was 11–16 days for SBCR and CM + SBCR but no sufficient cocoons were available for incubation from AW. Hatching success was 88%, 82% and 68% in CM, CM + SBCR and SBCR, respectively. Similarly, the highest mean number of hatchlings per cocoon was 3.08 ± 0.73 from CM. Consequently, earthworm offtake in CM, CM + SBCR, AW and SBCR was 86%, 78%, 70% and 62%, respectively. These results demonstrate that the type of organic substrate influence reproductive biology, growth and offtake of E. eugeniae, but suggesting that inadequately aged substrates negatively impact cocoon production and may cause earthworm death.