Effect of different levels of earthworm (Eisenia fetida) meal on some of growth parameters and skin pigmentation in Oscar (Astronotus ocellatus) fry

This study aimed to investigate the effect of replacing a commercial feed with different ratios of earthworm meal (0 (Control), 5, 10, and 15%) on growth parameters and skin pigmentation in Oscar fry. For this purpose, the experiment was performed in a completely randomized design with four treatments and three replicates. One hundred and twenty of Oscar fry with an initial average weight of 4.32±0.35g were dispersed into 12 aquaria. The stocking density was 10 fingerlings per aquarium. After 8 weeks, three fish from each treatment were randomly selected to measure the studied characteristics. The highest final weight (18.31±0.49 g), specific growth rate (2.51±0.11 %/day), survival rate (100 %), and the best food conversion ratio FCR (1.74±0.14) were observed in the fish fed with 5% earthworm meal compared to others (p<0.05). Total carotenoid at all treatments was significantly higher than the control group (p<0.05). The mean level of a* and b* factors in treatments replacing with 5 and 10% of earthworm meal was significantly higher than the control group (p<0.05); While, L* factors in mentioned levels (5 and 10%) was significantly lower than the control group (p<0.05). In conclusion, the results of this study showed that replacing the commercial feed with earthworm meal at 5% had positive effects on growth parameters and skin pigmentation factors in Oscar fry.