Abstract
Mealworm larvae (Tenebrio molitor) are edible insects consumed in feed and food. In the current study, the optimal harvesting time of mealworm larvae for use as aquafeed was investigated during the ages of 30–90 days after hatching (DAH). Development of digestive enzymes, proximate composition, and in vitro protein digestibility using digestive enzymes from African catfish (Clarias gariepinus) and Nile tilapia (Oreochromis niloticus), were used as criteria. The specific activities of pepsin and trypsin significantly decreased with age (p < 0.05) from the first harvesting time until 50 and 45 DAH, respectively, while steadiness in these enzyme activities was observed onwards. Chymotrypsin specific activity appeared constant across all harvesting times. The specific activity of amylase significantly decreased in the later stages of development, while cellulase exhibited a different pattern suggesting it has a major role in dietary fiber utilization relative to starch. Regarding proximate compositions of the mealworm larvae, the moisture and ash contents decreased significantly with age, while the protein content exhibited the opposite trend with the highest contents from 60 to 90 DAH. Crude lipid was generally fairly constant, but its lowest value was observed in the earliest stage. In vitro protein digestibility was not significantly different across all harvesting times for both fish species, except for the significantly decreased digestibility value at 65 DAH relative to 30 and 35 DAH for Nile tilapia. However, based on the economic benefits of time for growth increment and proximate chemical composition, approximately 60 DAH is proposed as suitable for harvesting mealworm larvae to be used in fish feed.
Highlights
Mealworm larvae (Tenebrio molitor) are edible insects consumed by people in many Asian countries, in Southeast Asia [1]
Digestive enzymes in mealworm larvae were genetically programed across thirteen developmental stages since only one type of feed was used throughout the experiment
The proximate composition of the mealworm larvae varied with the developmental stage, with protein being the major constituent, which is why they could be an excellent source of protein
Summary
Mealworm larvae (Tenebrio molitor) are edible insects consumed by people in many Asian countries, in Southeast Asia [1]. They are generally found as street food alongside other edible insects, and they can be applied in making a healthy snack food. They are typically used as live feed for pets and zoo animals, including birds, reptiles, small mammals, amphibians, and fish, and they can be used in canned, dried or powdered forms [2,3]. Mealworm larvae have received growing interest in the list of potential protein sources for food and feed.
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