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.

中文翻译：

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黄粉虫幼虫（黄粉虫）消化酶的本体发育及其用作鱼饲料的适宜收获时间。

黄粉虫幼虫（黄粉虫）是在饲料和食物中消耗的食用昆虫。在当前的研究中，调查了在孵化后30-90天（DAH）年龄中用作水产饲料的粉虫幼虫的最佳收获时间。使用来自非洲cat鱼（Clarias gariepinus）和尼罗罗非鱼（Oreochromis niloticus）的消化酶开发消化酶，其组成和体外蛋白质消化率均作为标准。胃蛋白酶和胰蛋白酶的比活性随年龄的增长而显着降低（p<0.05）从第一次收获到分别达到50和45 DAH，然后开始观察到这些酶活性的稳定。在所有收获时间中，胰凝乳蛋白酶的比活性均保持恒定。淀粉酶的比活性在发育后期显着降低，而纤维素酶表现出不同的模式，这表明相对于淀粉而言，淀粉酶在膳食纤维利用中具有重要作用。关于粉虫幼虫的最近组成，水分和灰分含量随着年龄的增长而显着下降，而蛋白质含量则呈现相反的趋势，含量从60到90 DAH最高。粗脂质通常相当恒定，但在最早阶段观察到其最低值。两种鱼类在所有收获时间的体外蛋白质消化率均无显着差异，但尼罗罗非鱼在65 DAH时的消化率值相对于30和35 DAH时显着降低。但是，基于时间的经济利益，可以增加生长量和接近化学组成，因此建议将大约60 DAH用作捕捞拟用于鱼饲料的粉虫幼虫。