Fish have low ability to absorb sugar, protein is the main nutrient for fish growth, most of which must be obtained from food, so the protein content of aquatic feed is generally required to be much higher than that of livestock feed, only in this way can the healthy growth of fish be guaranteed. In essence, fish and shrimp do not need protein but amino acids. However, animals cannot synthesize amino acids from simple inorganic materials, but must obtain amino acids directly or indirectly from the intake of animal and plant bait. Therefore, fish and shrimp feed should not only pay attention to the quantity of protein, but also pay attention to its quality.
High protein content will not only cause the waste of feed protein resources, may cause hepatobiliary disease, fish body obesity, like human obesity, but also increase the pressure of pond water quality management. The high protein content of fish can not be metabolized, so they will discharge more organic waste into the water, which not only increases the cost, but also causes damage to the water environment, forming eutrophic fat water.
Too low protein content, on the one hand, will cause slow growth of fish, poor disease resistance, on the other hand, will delay the production time. Too low protein content can not meet the physiological needs of the fish body, malnutrition, poor growth, bait coefficient will be high, sometimes also cause physical weakness and disease.
1. The feed protein nutrition of fish with different feeding habits and different growth stages is different.
Different species of fish, different stages of growth, its optimal protein requirements are also different. Carnivorous fish require a diet high in protein, while vegetarian fish require less protein. The appropriate protein content is generally below 30% for herbivorous fish (such as grass carp), 30-35% for omnivorous fish (such as carp) and 35-40% for carnivorous fish (such as catfish).
In order to meet the urgent physiological needs of new life, the nutritional requirements of fish in the stage of seedling should be high, while the nutritional level of fish in the stage of seedling or finished product can be appropriately reduced. Therefore, it is of great benefit to master the optimal protein level of fish feed for guiding fishery production.
The optimal protein content of tilapia fish should be 32% ~ 40% in the stage of juvenile period, 35% ~ 40% in the stage of seedling and 25% ~ 35% in the stage of adult fish.
Catfish, mullet and other carnivorous fish, the optimal protein content in the seedling stage is more than 40%, the optimal protein content in the adult stage is more than 35%.
2. Protein content in feed should be adjusted appropriately for different water temperatures.
For example, the protein content should be relatively reduced in the high temperature season like people eat a little light in the hot summer, in order to facilitate the digestion and absorption of fish, otherwise there will be fatty liver and other phenomena. Similarly, the protein content of the feed should be relatively increased in the low temperature season, just like people eat some dog meat and mutton in winter, so as to increase the heat savings of the fish body to dissolve the erosion of the body by freezing, so as to ensure the energy required by the metabolism and growth of fish.
3. The feed protein index of fish should be mainly animal protein.
Protein by sources of raw materials can be divided into two major categories of animal protein and vegetable protein, including fish meal, meat and bone meal and blood meal, etc are rich in animal protein, because of these proteins contain amino acids and amino acids required for the fish to grow, so the protein is not simply the absorption rate is high, but also absorb quickly, the low degree of water pollution, Therefore, the protein of high quality aquatic feed should be based on this animal protein. However, cottonseed meal, alfalfa meal and rapeseed meal mainly contain plant protein, which is used as the main raw material to produce aquatic feed fish absorption rate is low, slow absorption, serious pollution to water quality.