Marine fish actively drink sea salt water, providing the necessary level of water for normal functioning, and excess salt is removed from the body. The exchange of chlorine ions, sodium, potassium between the organism and the environment both in freshwater and marine fishes occurs through special chloride cells located in the gills, but in freshwater they are used to remove metal ions from water, and at sea to remove them from the body. This process is connected with energy expenditure, as occurs against the gradient. Energy is provided by the involvement of sodium and potassium. “Gill pump” that creates the possibility of a permanent replenishment of salts in freshwater fish, has high efficiency and is able to extract sodium and chloride ions from water millimolar and even lower concentration. Table salt since ancient times used in feed for fish as a preservative, to increase the appetite of fish, improve the absorbability, promote growth, and juvenile anadromous fish in which to prepare for the marine period of life. Due to the active exchange of sodium and chlorine with the environment, their constant intake of fish and disposal along with a large volume of liquid fish not afraid of high content of sodium chloride in the feed.
The absorption of potassium is much higher than other macro – and micronutrients from different food products. Despite the high content and availability of potassium from the commonly used fish feed ingredients, the addition of potassium to kormov 1.6 g/kg improves growth rate.
Sulfur is a sulfur-containing amino acids methionine and cystine, which take part in the formation of protein and other essential for life compounds (glutathione, insulin, etc.). Entering into the composition of the protein amino acids, sulfur is prevalent in almost all tissues and organs of fish. The main flow of sulfur in the body is protein, a small amount of it comes with some sulfur-containing vitamins — thiamine, Biotin.
Sulphur can be absorbed from the water, but from food it arrives in much larger quantities — up to 100 times more than water. Because it is part of the essential amino acid methionine and certain vitamins, the intake of sulfur depends on the content of these nutrients in the feed. Special additives of sulphur in the diet of fish is not required. During the metabolism of sulfur appears in a lot of water’.
Essential trace elements for fish are iron, copper, manganese, zinc, cobalt, selenium, iodine, chromium. There is anecdotal evidence of a positive impact on fish of very small amounts of molybdenum, Nickel, vanadium. To highly toxic trace element for animals and humans include mercury, cadmium, lead, arsenic.
Iron is part of the respiratory pigment hemoglobin, which binds and carries oxygen. Remasterizada in the composition of enzymes catalyzing respiration, iron is actively involved in redox processes. Compared to mammals, fish have very low amounts of iron due to small blood volume. 1 g fish contained 2-3 times less of this element than in mammals. As an integral part of the hemoglobin molecule contained in the red blood cells, iron is consumed very sparingly, making the circulation in the body. The destruction of red blood cells In th iron is again used for the synthesis of hemoglobin.