Potentials of Leaf Meal and their Protein Concentrate in Aquafeed

Abstract

The quest to sustain current aquaculture growth trend has necessitated the search for alternative feed ingredients in the light of conventional ones whose supply have dwindled and have become prohibitive. A major group of under-utilized, renewable, abundant and cheap unconventional source is leaf meal. They can be derived from the vast array of terrestrial and aquatic plants; most of which are nutrient-rich with little or no direct relevance in human nutrition. The nutritional composition of leaf meals usually varies widely; depending on plant cultivars from which they are derived, soil and climatic conditions, richness of medium in which they grow in case of aquatic plants, age and maturity of plants among other factors. Their limitation in fish nutrition is usually improperly balanced amino acid profile with methionine and lysine often limiting; nutritional-stress factors such as tannins, phytic acid, protease inhibitors among others; high fibre and palatability. The significance of these limitations is evident in impaired growth and reduced digestibility. Several efforts such as soaking, sundrying, fermentation, enzyme or amino acid supplementation have proven to be useful in improving the nutritional composition of leaf meals such that they are incorporated in aquafeed at higher inclusion levels relative to their raw state. Production of proteins from green leaves provide means of reducing antinutrients and high fibre contents associated with leaf meals while also providing a rational and sustainable strategy of sharing leaf resources among ruminants and non-ruminants. The technology of leaf protein extraction from green leaves may be increasingly relevant in future aquafeed if the drawbacks associated with its production are addressed. Further empirical information through intensified and co-ordinated research on the utilization of available leaf meals, either as protein or energy source, is needed to ensure feed security in aquaculture production.