The Influence of Wet Feed pH on the Growth of Tenebrio molitor Larvae

For optimal growth, Tenebrio molitor needs both dry feed and wet feed. Storing dry feed is not a problem, but storing wet feed over a prolonged period is more challenging due to spoilage. It could be stored in a refrigerated room, but this process is energy consuming and therefore increases the price of production. Another option is to ferment the feed, as is done regularly in other branches of agriculture. No energy is needed, and the feed remains stable due to low pH levels. In this study, we assessed the growth of mealworm larvae fed with wheat bran and agar-agar gel. Different treatments received agar-agar gel of a specific pH, varying between 3 and 9 in increments of one pH unit, resulting in seven assessed pH values. The average weight of the larvae was determined every week until maximum weight was achieved. Mealworms at harvest grown at the lowest pH (3.02) were on average 8.1% lighter than their counterparts grown at higher pH levels. However, within ranges that could realistically occur in a mealworm production setting (pH > 3.5), no significant differences were found. In conclusion, fermentation can be used to store mealworm wet feed, without pH having a detrimental effect on mealworm growth.