Table of Contents
The importance of fish feed formulation in aquaculture cannot be overstated. As the global demand for fish products continues to grow and the aquaculture industry continues to expand, the provision of high-quality, efficient and cost-effective fish feeds has become a key issue. At the same time, factors such as aquaculture environment and seasonal changes also affect the appetite and nutritional requirements of fish. Therefore, in-depth research on fish feed formulation is of great practical significance.
Basic ingredients in fish feed formulations
Nutritional Composition
Protein: Protein is a key nutrient for fish growth and the maintenance of body structure, consisting of amino acids, which are essential for muscle development, enzyme and hormone synthesis. High – quality protein sources, which are key fish feed ingredients, include fish meal, soybean meal, and meat and bone meal. Fishmeal is rich in a wide range of essential amino acids and closely aligns with fish needs, effectively promoting growth. Soybean meal, on the other hand, is a more affordable, plant – based protein source. However, care must be taken to ensure an optimal amino acid balance, especially in carnivorous fish feeds. To meet protein needs, fishmeal can be used in higher proportions for carnivorous species, while omnivorous and herbivorous fish can be supported with a mix of plant proteins like soybean meal.
Fat: Fat serves as an essential energy source and is crucial for maintaining cell structure, synthesizing hormones, and promoting vitamin absorption. Fish oil is a high – quality fat source, rich in essential omega – 3 and omega – 6 fatty acids like EPA and DHA, which improve immune response and stress resistance in fish. Vegetable oils such as rapeseed oil and sunflower oil can also serve as fat sources, but their digestibility must be considered. The fat requirements of fish vary, with cold – water species requiring higher levels of unsaturated fatty acids for physiological functions, whereas warm – water species have relatively lower fat requirements. Therefore, the type and level of fats in feeds should be adjusted based on species and growth stage.
Carbohydrates: While fish have limited ability to utilize carbohydrates, including them in moderation helps save on protein consumption. Wheat flour and corn are common carbohydrate sources, with wheat starch offering better digestibility and stability in water. It’s essential to choose carbohydrates based on the fish’s digestive capabilities and feed processing methods. Wheat flour helps improve feed pellet stability, ensuring reduced nutrient loss in water.
Vitamins and Minerals: Vitamins and minerals are vital for various physiological functions such as growth, immune response, and reproduction. Water – soluble vitamins (e.g., vitamin C and B vitamins) and fat – soluble vitamins (e.g., vitamins A, D, E, and K) play indispensable roles in metabolism, antioxidant functions, vision, and bone development. Minerals such as calcium, phosphorus, magnesium, and iron contribute to bone development, osmotic pressure regulation, and nerve function. Since fish are unable to synthesize many of these nutrients, they must be sourced from feeds, making vitamin and mineral premixes an essential part of feed formulations.
Additives
Colorants: The addition of colorants, such as spirulina, astaxanthin, and synthetic carotenoids, can enhance the marketability of farmed fish by improving their coloration. Astaxanthin is commonly used to enhance the red/pink pigmentation in species like salmon. The addition of spirulina not only provides color but also boosts the fish’s immune system due to its nutrient content.
Binders: The role of binders is to maintain feed particle stability in water, reducing nutrient loss and ensuring effective feed utilization. Common binders include starch, cellulose, pectin, and gelatin. The binder choice depends on the feed type, with floating feeds requiring binders that offer buoyancy, and sinking feeds needing stable binding agents.
Preservatives: To extend shelf life and prevent fat oxidation and microbial growth, preservatives are used. Vitamin E (a natural antioxidant), BHA, and BHT are common preservatives, ensuring feed quality over time. Preservatives also contribute to the storage stability of feeds, minimizing nutrient degradation.
Food Attractants: To improve palatability and stimulate fish feeding, food attractants such as fish hydrolysates, glycine, and betaine are added. These additives enhance the feeding motivation of fish, particularly when switching to new feeds, thereby improving feed conversion rates and growth performance.
Steps of Feed Formulation
Determine the Nutritional Requirements
The nutritional requirements of fish vary significantly among species, growth stages, and culture environments. For instance, juvenile fish require higher protein levels for rapid growth, while adults need more balanced energy intake. It is essential to reference relevant nutritional data and industry standards to ensure the formulated feed meets fish needs. Environmental factors, such as temperature and water quality, also influence these requirements. For instance, fish in high – temperature environments exhibit increased metabolic rates and require more energy, while those in poor water quality may need additional vitamins and minerals to boost immunity.
Selection of Raw Materials
The selection of raw materials, which are the fish feed ingredients, must be based on nutritional requirements, availability, and cost – efficiency. Fishmeal, soybean meal, and other plant proteins such as algal protein and insect protein can be considered. Insect protein offers high amino acid content and is an environmentally friendly option. Algal proteins are rich in nutrients beneficial for fish health. The fat sources (fish oil, vegetable oils, or microalgae oil) should be chosen according to the fatty acid profile required by the fish. The quality control of raw materials is crucial to ensure feed safety and nutritional integrity.
Calculate Proportions
Pearson Square Method: The Pearson Square method is a simple and practical calculation method suitable for formulating feeds with two raw materials. For example, if you want to prepare a feed with a protein content of 30%, and you have fishmeal (with a protein content of 60%) and wheat bran (with a protein content of 15%). First, write the protein content of fishmeal and wheat bran in the upper – left and lower – left corners of the square, respectively, and write the target protein content of 30% in the middle. Then calculate the proportion of fishmeal and wheat bran in the feed. The proportion of fishmeal is (30 – 15) / (60 – 15)=33.3%, and the proportion of wheat bran is (60 – 30) / (60 – 15)=66.7%. This method is simple and intuitive, which is very helpful for small – scale farmers or beginners to initially determine the feed formula. However, its limitation is that it can only consider one nutrient at a time and is only applicable to the situation of two raw materials. For complex multi – raw – material formula calculations, it is not very suitable.
Linear Programming Method: For complex formulas with multiple raw materials, the linear programming method can be adopted. This method establishes a mathematical model, comprehensively considering factors such as the nutritional composition, price, and supply limitations of raw materials, to achieve the goal of minimizing feed costs while meeting the nutritional needs of fish. For example, if there are multiple raw materials such as fishmeal, soybean meal, corn, and wheat flour, and you want to prepare a feed that meets the nutritional needs of specific fish, and at the same time, you need to consider the market price and inventory of these raw materials. Through linear programming software, the objective function can be set to minimize the feed cost, and the constraint conditions include the minimum and maximum content requirements of various nutrients, the usage limitations of raw materials, etc. Then solve this mathematical model to obtain the optimal dosage ratio of various raw materials. This method can optimize the feed formula more accurately, but it requires certain mathematical knowledge and professional software support. There are also some fish feed formulation calculators available that use this principle to help users quickly calculate the proportion of different ingredients based on input parameters.
Trial – and – Error Method: The trial – and – error method is a more traditional method. It involves continuously trying different combinations and proportions of raw materials, observing the growth effect and feed utilization rate of fish, and gradually adjusting the formula. In practical applications, first, initially determine the types and approximate proportions of raw materials based on experience or by referring to similar successful formulas. Then, prepare a small amount of feed for feeding experiments. Observe the feeding situation, growth rate, and health status of fish, and adjust the formula according to the test results. For example, if it is found that the fish grow slowly, it may be that the protein content is insufficient or the amino acid balance is not good. It is necessary to appropriately increase the proportion of high – quality protein raw materials or adjust the dosage of amino acid additives. Although this method is relatively cumbersome and time – consuming, it has certain flexibility and practicality for the formula design of some new raw materials or under special breeding conditions.
Trial – and – Error Method: The trial – and – error method is a more traditional method. It involves continuously trying different combinations and proportions of raw materials, observing the growth effect and feed utilization rate of fish, and gradually adjusting the formula. In practical applications, first, initially determine the types and approximate proportions of raw materials based on experience or by referring to similar successful formulas. Then, prepare a small amount of feed for feeding experiments. Observe the feeding situation, growth rate, and health status of fish, and adjust the formula according to the test results. For example, if it is found that the fish grow slowly, it may be that the protein content is insufficient or the amino acid balance is not good. It is necessary to appropriately increase the proportion of high – quality protein raw materials or adjust the dosage of amino acid additives. Although this method is relatively cumbersome and time – consuming, it has certain flexibility and practicality for the formula design of some new raw materials or under special breeding conditions.
Adjustment and Optimization
After initially determining the formula, small – scale experimental feeding is required to observe the growth performance, health status, and feed conversion rate of fish. Adjust and optimize the formula according to the test results. If the growth rate of fish is not satisfactory, it may be necessary to check whether the ratio of protein and energy is appropriate and whether there is a lack of certain essential amino acids or fatty acids and other nutrients. If the feed conversion rate is low, it may be necessary to adjust the digestibility of raw materials or add additives to promote digestion and absorption. At the same time, factors such as the stability and palatability of the feed in water also need to be considered. For example, if the feed disintegrates too quickly in water, it is necessary to increase the amount of binder or replace it with a raw material with better binding performance. If the fish are not enthusiastic about eating the feed, it may be necessary to adjust the type and amount of attractant. Through continuous experiments and adjustments, a feed formula that can not only meet the nutritional needs of fish but also has good economic benefits and environmental friendliness can be finally determined.
Specific Formulations of Fish Feeds
Examples of Common Fish Feed Formulas
Carp Feed: Carp is an omnivorous species, and its feed may contain 40% fishmeal, 30% soybean meal, 15% wheat bran, 10% corn, and 5% vitamin – mineral premix. This provides a balanced mix of proteins, carbohydrates, and essential nutrients. Adjustments can be made based on growth stages, such as increasing protein content for juveniles or reducing it for adults to lower cost.
Grass Carp Feed: For herbivorous grass carp, a formula consisting of 50% rice straw meal, 20% soybean cake, 15% rice bran, 10% fish meal, and 5% additives supports digestion and ensures a balanced diet. Green feeds like alfalfa can be added seasonally for improved palatability and nutrition.
Perch Feed: As a carnivorous fish, perch requires a high – protein diet. A suitable formulation for perch includes 60% fishmeal, 20% shrimp meal, 10% wheat flour, and 10% fish oil, along with a vitamin – mineral premix.
Special - Purpose Feed Formulations
Ornamental Fish Feed: For ornamental fish, apart from meeting their nutritional needs, color enhancement is essential. The feed can include astaxanthin, spirulina, and high – quality protein sources to improve color and health.
Fry Feed: Since fry have underdeveloped digestive systems, their feed needs to be finely ground and highly digestible. A common formula for fry feed includes 60% fishmeal, 25% soybean meal, and 15% corn flour, ensuring rapid growth and immune support.
Scientific Feeding Methods
Control of Feeding Amount
Based on Fish Weight and Growth Stage: The feeding amount should be adjusted reasonably according to the weight and growth stage of fish. Generally, the feeding rate is relatively high at the juvenile stage and gradually decreases as the fish grow. For example, the daily feeding rate may reach 5% – 10% of the body weight of the fish during the nursery stage, while the feeding rate may be reduced to 1% – 3% of the body weight of the fish during the later stages of adult fish culture. Fish can be sampled and weighed at regular intervals, and the feeding rate can be adjusted according to changes in body weight and growth to ensure that the fish receive sufficient nutrients without causing feed wastage and water pollution.
Observing Fish Feeding Behavior: During the feeding process, closely observe the feeding behavior of fish. If the fish quickly finish eating the feed in a short time and show signs of continuing to forage, it indicates that the feeding amount may be insufficient, and the feeding amount can be appropriately increased; if the feed remains for a long time after feeding and the fish are not interested in the feed, it may be that the feeding amount is too much or the feed palatability is poor, and the feeding amount needs to be reduced or the feed formula needs to be adjusted. At the same time, it is necessary to avoid over – feeding, so as not to cause problems such as obesity, decreased immunity of fish, and water quality deterioration.
Feeding Frequency
According to Fish Species and Habits: Different species of fish have different feeding habits, and the feeding frequency should be adapted to them. Some carnivorous fish such as sea bass and mandarin fish usually have strong feeding abilities and fast digestion speeds, and the number of feedings can be appropriately increased, but the amount of each feeding should not be too much; while some herbivorous fish such as grass carp and pomfret have relatively slow digestion, and the number of feedings can be relatively less. For example, carnivorous fish may need to be fed 3 – 4 times a day, while herbivorous fish can be fed 2 – 3 times a day.
Avoid Excessive One – Time Feeding: Dividing the daily feeding amount into multiple feedings helps to improve the feed utilization rate and reduce water pollution. For example, the feed for one day can be divided into three feedings in the morning, noon, and evening, and the amount of each feeding is reasonably allocated according to the fish’s feeding situation and growth stage. This can prevent the fish from ingesting too much feed in a short time, reduce the burden on the digestive system, and at the same time help maintain the stability of water quality.
Feeding Time
Choose the Appropriate Time Period: Generally, choose to feed during the day when the water temperature is suitable and the fish are active. For most fish, 8:00 – 10:00 am and 3:00 – 5:00 pm are more suitable feeding times. During this time period, the water temperature is relatively stable, and the fish have a strong appetite and can better ingest and digest the feed. Avoid feeding at night or during periods when the water temperature is too low or too high, so as not to affect the digestion and health of the fish.
Maintain Regularity: The feeding time should be relatively stable, so that the fish can form a good feeding biological clock. This can improve the fish’s feeding enthusiasm and feed utilization rate, and is also convenient for farmers to manage. For example, feeding at a fixed time every day, the fish will gradually adapt to this rule and will actively gather in the feeding area when the feeding time arrives, improving the feeding effect.
Conclusion
The formulation of fish feeds is an evolving science that requires in – depth research into the nutritional needs of specific fish species, the availability of quality raw materials, and the technological advancements in feed manufacturing. By ensuring nutrient balance, optimal digestibility, and feed stability, we can promote sustainable aquaculture, reduce costs, and improve the quality of farmed fish. Moreover, future research into alternative proteins and environmentally sustainable ingredients will further enhance the sustainability of the industry, reducing the environmental impact while meeting the growing demand for fish products.
