Fishmeal replacement by mealworm (Tenebrio molitor) in diet of farmed Pacific white shrimp (Litopenaeus vannamei): effects on growth performance, serum biochemistry, and immune response

Reducing the use of fishmeal (FM) in shrimp feed means significant savings in the amount of FM consumed globally and subsequently reducing production costs and environmental impacts. Insect meal (IM) is one of the protein sources to replace FM in aquafeeds. In this regard, this study was conducted with the aim of investigating the effect of replacing FM with mealworm (MW, Tenebrio molitor) on the growth performance, haemolymph biochemical responses, and innate immunity of Litopenaeus vannamei. Shrimps with a mean weight of 7.41 ± 0.13 gram were cultured in 300-liter fiberglass tanks (with a useful drainage volume of 200 liters) with a density of 20 shrimp per tank over a period of 60 days. Dietary treatments, including the control treatment (no mealworm; T0), 15% (T15), 30% (T30), 60% (T60), and 100% (T100) level of replacing FM with mealworm (MW), each with three replications, were investigated in the form of a randomized design. The results of this study showed a significant difference in body weight gain (BWG), feed efficiency (FE), feed conversion ratio (FCR), and hepatopancreas index (HPI) among the treatments (P < 0.05). With the increase of the replacement of FM with MW up to 30%, BWG, FE, and HPI were significantly increased then reduced. The levels of cholesterol (Chol), triglycerides (Tg), and glucose (Glu) showed a decreasing trend with increasing replacement of FM with MW and revealed a significant difference with the control treatment at high levels of replacement (P < 0.05). Besides, the results showed that replacing FM with MW had a significant effect on the activities of superoxidase dismutase (SOD), phenol oxidase (PO), lysozyme (LZM), acid phosphatase (ACP), alkaline phosphatase (ALP) and the total count of hemocytes (THC) in the practical diets compared to the control group (P < 0.05). Overall, the findings suggest that MW is a promising alternative protein source for L. vannamei, as it enhances both growth performance and the immune system. The study recommends the use of MW in the diet of farmed species in the aquaculture industry, given its lack of adverse impacts on growth performance and its potential to reduce environmental consequences resulting from its production. The results also underscore the importance of exploring alternative protein sources to reduce dependence on FM and enhance sustainability in the aquaculture industry.