Learn What Marine Fish Eat
Proteins, amino acids, fatty acids, carbohydrates, vitamins, minerals, energy, energy/protein balance are the essential elements of an animal diet.
The object of feed formulation is to mix ingredients of differing nutritional quality so as to obtain a balanced diet whose biologically available nutrient profile approximates to the dietary needs of the animal in question.
However, the formulation of a practical diet is largely a compromise between what would be ideal from a nutritional viewpoint (i.e. such as the production of a diet in which the protein component is entirely supplied by a high quality fish meal), and what is practical and economical.
According to the F.A.O. the following factors should be considered when formulating a practical fish or shrimp ration:
1. Market value of the species to be farmed: feed cost should not exceed 20–25% of the farm gate value of the cultured fish or shrimp
2. Feeding behaviour and digestive capacity of the farmed species: Is the species a carnivore, omnivore or herbivore; a benthic, pelagic or surface feeder; a day-time, twilight or nocturnal feeder; a visual or olfactory feeder; a moist or dry diet feeder; a rapid or slow feeder; and does the species in question have an acid secreting stomach and possess a full compliment of digestive enzymes?
These factors, together with the proposed production unit (i.e. tank, cage or earth pond) will dictate if a floating, slow-sinking or sinking feed is required, and will also determine the physical characteristics of the feed to be produced (i.e. size, bouyancy, colour, texture, palatability and desired water stability).
Similarly, the formulation of a diet for a stomachless fish species or a shrimp will necessitate the use of dietary phosphorus and calcium sources which release their native elements within an alkaline digestive environment
3. Intended feed manufacturing process to be used: straight mixing, cold pelleting, conventional steam pelleting, expansion steam pelleting, flaking, crumbling or microencapsulation.
For example, expansion steam pelleting requires the presence of relatively high amounts of starch containing cereal grains within the formulation so as to facilitate starch gelatinization and obtain the desired expansion texture.
Cold pelleting techniques require the use of special binders which do not have to be activated by heat (i.e. such as the use of alginate binders within semi-moist pelleted fish feeds); and micro-encapsulation techniques for larval shrimp require the use of soluble and highly digestible dietary protein sources such as egg proteins and invertebrate tissue homogenates
4. Dietary nutrient requirements of the farmed species: including the dietary protein, essential amino acid, essential fatty acid, vitamin, mineral and energy (if known) requirements for all stages of the life cycle.
5. Available feed ingredient sources: This includes the nutrient content of available feed ingredients, including quality control and cost (at source and with transportation).
The availability, nutritional quality and cost of individual feedstuffs (including micro-nutrient sources such as vitamins, minerals, amino acids, antioxidants and mould inhibitors) will dictate the type of ration which can be formulated
