Micro-ingredients for aquafeeds : the importance of product formulation

Micro-ingredients are a group of essential or beneficial compounds included in small quantities in the diet of animals. They include vitamins, minerals, carotenoids, amino acids, enzymes, attractants and immunostimulants. These feed micro-ingredients must resist prolonged contact with possibly aggressive components in premix concentrates. They must be handled with great precision in the feed mill and they must withstand the aggressive processes commonly experienced in the aquaculture feed industry. Indeed, most of the active substances are sensitive to factors such as temperature, oxygen, humidity, light and pH. In order to preserve their nutritional functions, it is necessary to optimize four major characteristics of the active substance: bioavailability, stability, handling and miscibility. This is achieved by formulating the active ingredients into product forms using appropriate processes and high quality auxiliary materials. A broad variety of processes can be used to ensure the quality of the products. The selection of the process and materials used depends on the nature of the substance to be formulated and the application foreseen. Vitamin C is prone to oxidative degradation, but does not require the same level of protection when it is used to supplement a pelleted broiler feed compared to when it is used to supplement extruded tilapia feed. Formulation processes include encapsulation of the active substance in a matrix or a cross linked matrix, coating, spray-drying, adsorption and high shear granulation. Furthermore, heat labile substances can be esterified in order to become stable. The art and science of product formulation enables the microingredient manufacturer to transform an unstable molecule into one that is stable, while not reducing the bioavailability of the active substance. It is therefore important for the fish or shrimp nutritionist to be well informed on the major characteristics of micro-nutrients in order to select the best product for a given application. This paper reviews formulation techniques and simple tests to evaluate the quality of formulated micro-ingredients.