By: Dr Mustapha ABA, Aquaculture Scientific Expert. Fish Nutrition.Rabat. Morocco.
In this article, the objective is not to solve all the problems related to aquafeeds, but rather to find solutions to the problems of feed choice in aquaculture, both on the part of the aquaculturist who must require the quality of feed, and on the part of food manufacturers who must be interested in the nutritional efficiency of their products that they sell as aquaculture feed.
Introduction
In aquaculture, nutrition and food are directly linked to the level of productivity and economic efficiency of farming systems, promoting the maintenance of fish health, influencing their performance and, consequently, the nutritional quality of their fish and shrimp meat, the main end product that will be supplied to the consumer market.
For these reasons, research in fish nutrition and feeding has been directed towards the formulation of feeds with high nutritional value, high digestibility, properly balanced to achieve maximum productivity of different fish species, and which minimise production costs, increase product quality and reduce the discharge of organic waste.
Many factors can influence the quality of the food, as each ingredient in the formulation has its own characteristics, taking into account the many factors that can influence the nutritional needs of aquatic animals such as sex, lineage, growth phase, physiological state, production systems and production regimes, water temperature.
However, for the aquaculturist, the best way to measure the quality of the feed is to measure the performance of the fish. However, rapid growth is not always a sign of good nutrition. It is necessary to check the internal organs, in particular the liver, which may be friable and abnormally coloured, or the quality of the carcass (measured mainly by the visceral fat content) is another indicator of the good nutritional status of the fish.
In this context, when choosing foods, it is necessary to assess not only their nutritional value, digestibility and cost, but also criteria related to sustainability and environmental impacts.
The nutritional quality of aquaculture feed depends on the nature and quality of the raw materials used in its composition, the nutritional approach adopted in the formulation of the products, as well as the equipment and manufacturing methods.
Some criteria in aquaculture should be taken into account before deciding which feeds to use. In this article, we will show you what these criteria are.
- Information on the aquaculture species
It is important to know each species you have with your breeder, because each fish has nutritional needs and behaviour during feeding.
It is necessary to have information such as: the species of fish raised, its feeding behaviour, feeding habits, pond size, stocking density, temperature and water quality.
- Knowing the nutritional needs of the farmed species
Meeting the nutritional needs of the species allows for better feed conversion and is expected to cause less damage to the environment.
- The nutritional composition of the feed
Good growth depends on the safety of aquatic animals to receive appropriate nutrient fractions proportional to their dietary needs. This is why food must necessarily contain adequate doses of protein and amino acids.
In addition to protein, the food must contain a content determined according to the species of lipids that are sources of unsaturated fatty acids, carbohydrates, vitamins and minerals.
- Ensure feed quality
It is extremely important for the aquaculturist to know the composition of the feed he is buying, in terms of protein, carbohydrate, fat, ash, dry matter and raw fibre levels. All this information must appear on the label of each food bag. Similarly, the aquaculturist may request a report from the feed manufacturer on its centesimal composition.
- Stability in water
It is important that the food has good stability in the water, so that it is visible to fish, this flotation or stability depends on the content of fat in the food and its processing at extrusion.
- Digestibility
Another important fact, which has not merited the attention of aquatic feed manufacturers, is related to nutrient digestibility. The better the digestibility of the feed components, the more efficient the feed is and more fish produce less feces , which will contribute to the respect of the aquatic environment.
- A better Digestible Protein to Digestible Energy Ratio.
In order to ensure protein savings with greater protein efficiency, for better growth the aquaculture feed must have a good PD/ED ratio, the latter can only be obtained through better use of fats and carbohydrates as an energy source.
- Particle content Fine
A quality food does not contain many fine particles. The quantity of these particles must be measured in each batch of purchased food. After screening the food, the residue (dust) must be weighed and must not exceed 1% of the total weight of the sampled bag.
- Type of food processing
The type of processing the food receives at the plant is also part of good fish feed management practices, so the ideal is always to offer extruded feed rather than granulated or friable feed. This is because extrusion promotes greater stability at the surface of the water, which makes it easier for the producer to visualize consumption.
- Price – quality ratio
Finally, it would be important to raise awareness among aquaculture producers so that the choice of aquaculture feed is not based on price or crude protein content, but on the performance it provides, which will ultimately depend on its quality. The possibility of reducing fish feeding costs can be achieved by a better feed conversion rate (FCR), which may be the main factor to be taken into account.
