Effects of Housefly Maggot Meal and Earthworms on Growth and Immunity of the Asian Swamp Eel Monopterus albus (Zuiew)

Abstract

Fly larvae (maggot meal) and earthworms are promising potential replacements for increasingly expensive and unsustainable fishmeal. Apart from being a good protein source, fly larvae also contain substances with immunostimulant capacity, however the impact of their inclusion in feed on the immune system remains only partially understood. To address this, we studied the effects of four diets with varying levels of earthworm (40-70%) and maggot meal (0-30%) on growth and immunocompetence of juvenile Asian swamp eels Monopterus albus (fish n = 480, duration = 40 days). Maggot meal inclusion resulted in a significantly (P<0.05) higher total protein, glutamic pyruvic transaminase activity, anti-oxidizing enzyme and lysozyme activity, and significantly lower triglycerides, in the blood serum. Bacterial (Aeromonas hydrophila) challenge test results showed that adding maggot meal to the feed improved survival rate and immunocompetence at all three tested inclusion ratios. The strongest positive impact on most studied parameters (including 50% higher survival and 21.4% higher immunocompetence) was observed in the 20% inclusion group. As positive effects were slightly lower at the 30% level, the optimal combination of the two ingredients was 20% maggot meal and 50% earthworms