With increasing population, the demand for dietary animal protein has increased. This highlights the crucial role of aquaculture in meeting the escalating global demand for nutrition. Sustainability and profitability of large-scale aquaculture production are strongly influenced by the availability and cost of feed, especially protein ingredients, which is not only the most expensive component but also a critical determinant of growth and feed efficiency. However, dependence on fish meal as protein source for aquafeed is increasingly unsustainable due to diminishing supply, escalating costs, and environmental concerns. Freshwater macrophytes such as duckweed (Lemna minor) offer a renewable alternative to traditional fishmeal due to their high nutritional value, rapid growth rates, and broad availability.
Anabas testudineus (Bloch, 1792), commonly known as the climbing perch, has high nutritional value, medicinal properties, and resilience, which makes it good candidate for aquaculture species expansion. However, its aquaculture production remains relatively limited compared to carps, primarily due to high feed costs driven by reliance on expensive animal-based protein ingredients. The development of cost-effective, digestible, and nutritionally balanced feeds is crucial for enhancing the aquaculture potential of A. testudineus. This study examines the potential of L. minor as a cost-effective, alternative protein source to traditional fishmeal in its feed. Juveniles of the fish were fed 60 days with test diets (TD) supplemented with graded levels of L. minor, viz., 0% (TD0), 5% (TD5), 10% (TD10), and 20% (TD20). Results indicate that a 15% inclusion of L. minor (TD15) resulted in optimal growth, feed conversion, and nutrient utilization without adverse effects. Significantly enhanced digestive enzyme activities and higher amino acid content were also observed in TD15 group. Immunoglobulin, lysozyme, alkaline phosphatase, and catalase activities were elevated in fish fed the L. minor-incorporated diet, while aspartate aminotransferase, alanine aminotransferase, superoxide dismutase activities, and thiobarbituric acid reactive substances remained unaffected. Polynomial regression analysis indicated an optimal inclusion range of 16.25% to 17.10%. These findings suggest that incorporation of L. minor in aquafeeds could substantially reduce production costs leading to sustainable aquaculture of the species.
Keywords: Anabas testudineus, digestive enzymes, Lemna minor, plant protein, sustainable aquafeed.