The Effect of Aging Duration of Organic Substrates on the Growth, Survival, Cocoon Production and Hatchability of African Night Crawler (Eudrilus eugeniae)

Abstract

Knowledge about the effects of aging duration of organic substrates on reproductive characteristics and growth of Eudrilus eugeniae is limited. However, as organic matter decomposes, nutrients such as nitrogen, phosphorus, and potassium are released and are recycled in various chemical forms through microorganisms that are eaten up by the earthworms. In order to promote vermiculture biotechnology on a large scale, it is therefore essential to understand the influence of substrate aging on reproductive and growth characteristics of the earthworms together with the substrate. This study assessed growth patterns and reproduction characteristics of the earthworm including, incubation period, hatching success and hatchlings per cocoon, biomass increase/earthworm/ day and offtake (i.e., percentage number of earthworms weighing at least 1.0 g in 77 days) of E. Eugeniae as affected by aging durations of four organic substrates. The substrates included abattoir waste (AW); cattle manure (CM), soya-bean crop residue (SBCR) in the ratio of 1:2 and a binary combination of cattle manure with soya-bean crop residue (CM+SBCR) mixed with dark loam soil in the ratios of 1:1:4. Results showed that mean growth rate was highest (17.1mg/worm/day) when grown on CM aged for 3-4 weeks, followed by that in AW (16.7 mg/worm/day) aged between 3 to 4 weeks, and lowest in SBCR (14.7 mg/worm/day) aged for 2 to 3 weeks (P<0.05). Cocoon incubation period ranged between 13 - 16 days for CM but it was 10 - 15 days for the SBCR and CM+SBCR. Hatching success was highest in CM (88.9%) aged 2-3 weeks followed by CM+SBCR (83% ) aged for 3-4 weeks and lowest in AW (57%) aged for 4 weeks. Highest mean number of hatchlings per cocoon was 3.0±0.2 observed in CM aged 3-4 weeks, however, this was not different (P>0.05) from 2.8±0.5 and 2.84±0.58 observed in CM+SBCR and SBCR aged for 3-4 weeks, respectively. Survivability was low in all substrates during the first 2 weeks of aging although all the worms died in the AW aged for only 1 week. Percentage offtake in the CM, AW, CM+SBCR and SBCR was 91%, 73%, 72 % and 70%, respectively, when aged for 2-3 weeks. These results demonstrated that aging duration of different organic substrates has an impact on reproductive potential, growth, and survivability of E. eugeniae