Reasons why the body color of yellow catfish (Pelteobagrus fulvidraco) cultured in flowing water cannot turn yellow
Why can't the body color of yellow catfish cultured in flowing water turn yellow?
Whether pond flowing-water culture or river culture, the body color of yellow catfish cannot turn yellow after being fed color-transition feed. I wonder if everyone has encountered the same problem. Please give some guidance, thank you!
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Is it because yellow catfish consume a lot of energy in flowing water, the fat added to the feed is not enough, and pigment deposition is poor?
Yellow catfish (Pelteobagrus fulvidraco) belongs to the order Siluriformes, family Bagridae, genus Pelteobagrus Bleeker, commonly known as ga fish, yellow aunt, yellow-fin fish, etc., and is widely distributed in rivers, lakes, ditches and other waters in China. Yellow catfish has a bright body color, tender meat and rich nutrition. It is a high-quality and precious economic fish, and has now become one of the species that can achieve relatively good economic benefits in artificial culture. In natural water bodies, because yellow catfish feed on a large amount of algae and plankton rich in carotenoids, their body color is relatively bright. Under normal conditions, there are black spots on the sides of the body, and the rest is yellow. Under artificial culture conditions, the main problem that appears is the change in body color, and because of the change in body color, the commercial value is seriously affected. In addition to factors affecting body color such as water environment conditions and disease, the most important cause of body color change in yellow catfish is the major impact of feed substances on its body color. In fact, the impact of feed substances on fish body color only reflects the impact of feed substances on the overall physiological function of the fish. Based on the results in actual production and under experimental research conditions, this article analyzes the main types of body color changes in yellow catfish and their correlation with feed substances, hoping to provide technical reference for the formulation, production and use of compound feed for yellow catfish.
1. Species characteristics and body color of the genus Pelteobagrus
There are 5 species in the genus Pelteobagrus. The characteristics of each species are respectively yellow catfish (P. fulvidraco), intermediate yellow catfish (P. intermedius), long-barbel (fork-tailed) yellow catfish (P. eupogon), Vachelli's (river) yellow catfish (P. vachelli) and glossy yellow catfish (P. nitidus). Different species have different body shapes and body colors. Some species have relatively bright coloration, while others are relatively
pale. The species mainly cultured artificially are yellow catfish and Vachelli's yellow catfish, with other species mixed in in small amounts. Therefore, when the cultured species are different, the body shape and body color of the fish will be very different. Under artificial culture conditions, if everyone hopes to achieve the body shape and body color of yellow catfish (P. fulvidraco), it cannot be realized. It is only possible to achieve the body shape and body color that the species should have in the natural environment according to the respective body shape and body color of different species.
2. Body color changes of yellow catfish under culture conditions and their relationship with feed
(1) Yellow catfish cultured in large water bodies
Large water body culture mainly refers to yellow catfish stocked in lakes and reservoirs, without feeding compound feed. The fish feed in the natural environment, and the main food includes aquatic insects and their larvae, small shrimp, mollusks and small fish, etc. Therefore, the fish body color is the natural body color, as shown in Figure 2, and the body color is relatively bright.
(2) Yellow catfish lacking yellow pigment
Yellow catfish cultured with feed have relatively normal black body color, but lack yellow body color; there are
relatively obvious black patches, but the skin color is relatively light, and no yellow body color appears (see Figure 3).
The black body color of fish mainly depends on the number and distribution density of melanocytes in the skin, as well as the distribution state of melanosomes in melanocytes. The yellow body color mainly depends on carotenoids absorbed by the fish from the feed, such as the deposition state of lutein in the skin. This type of pigment is fat-soluble and is absorbed, transported and deposited along with feed fat. Therefore, when the body color of yellow catfish appears as shown in Figure 3, it indicates that the nutritional level of the feed is insufficient, or the feed lacks carotenoids that can be absorbed and deposited. As long as corresponding adjustments are made, the body color of yellow catfish can return to normal.
(3) Yellow catfish with yellow body color
As shown in Figure 4, the black spots on the fish body basically disappear, but the yellow body color is relatively obvious. The reason for this phenomenon is the combined result of a decrease in the number and distribution density of mature melanocytes in the skin and the deposition of yellow pigments such as lutein and carotenoids in the skin and muscle. When the number and distribution density of mature melanocytes in the fish skin decrease, if there are relatively large amounts of lutein and carotenoids absorbed and deposited along with fat, the fish body will show a yellow body color.
Like the pigment cells of fish and other vertebrates, new pigment cells do not proliferate through cell division. Instead, neural crest cells migrate to the skin, eyes, etc., differentiate into prepigment cells, and then the prepigment cells differentiate to form young melanocytes, xanthophores and other pigment cells, and the young pigment cells then develop into mature pigment cells. Taking melanocytes as an example, neural crest cells migrate to the skin and eyes, etc., differentiate into premelanocytes, and then the premelanocytes differentiate into melanoblasts. The melanoblasts gradually grow and develop into mature melanocytes. Therefore, the formation of a mature melanocyte must go through several stages, including the migration of neural crest cells, differentiation of premelanocytes, development of melanoblasts, and growth of melanoblasts. During this period, it is regulated and controlled by various hormones and physiological factors. If a physiological error occurs in any link during this period, it will affect the migration, differentiation, growth and development of melanocytes, and lead to a decrease in the number and distribution density of mature melanocytes in the skin, thereby affecting the fish body. In addition to being affected by factors such as the culture environment and disease, it is also affected by feed factors.
Therefore, when this body color appears, it should be the result of feed substances seriously affecting the formation of mature melanocytes and relatively high absorption of carotenoids, indicating that the feed contains substances that can affect the normal physiological function of the fish, such as containing relatively large amounts of oxidized oil, containing melamine-type non-protein nitrogen, insufficient vitamins, etc. The quality of the feed formula and feed ingredients should be checked, and technical measures such as eliminating harmful feed substances and ensuring sufficient vitamins should be adopted.
(4) Yellow catfish with severely affected body color
As shown in Figure 5, the body color of yellow catfish shows severe changes. Both the black and yellow body colors of the fish are seriously insufficient, and the fish body shows albinism. This is the result of toxic and harmful substances in the feed causing severe damage to the physiological function of the fish. Based on the current situation analysis, the direct cause is that the feed ingredients contain melamine-type non-protein nitrogen, or relatively high doses of oxidized oil were used.
Any feed substance that can cause major changes in the physiological function of the fish will cause disorder of the overall physiological function of the fish, and further seriously affect the normal migration, differentiation, development and maturation process of fish pigment cells, and cause changes in fish body color. This kind of fish body color change shows a strong correlation with feed quality and the feed of different feed enterprises. Only after finding and removing this substance that causes major changes in fish physiological function, and after the physiological function of the fish gradually recovers, can the recovery of fish body color and the maintenance of normal body color be ensured. This should be the basic technical countermeasure for solving fish body color changes caused by feed substances.
From the analysis of the breadth and severity of the impact of feed substances on fish physiological function, at the current stage the main feed substances are mainly oxidized oils in feed and non-protein nitrogen such as melamine mixed into feed ingredients, followed by vitamins, minerals, especially some trace elements.
The impact of oxidized oils in feed on fish body color includes two aspects. First, after oxidized oils enter the fish body, they may continue to oxidize and produce relatively large amounts of oxygen free radicals or other free radicals. These free radicals can cause oxidation and breakage of unsaturated bonds in carotenoid molecules, causing carotenoid pigment substances to lose their pigment function and leading to degradation of fish body color. On the other hand, the impact of oxidized oils in feed on the physiological function of cultured fish can seriously affect pigment cells, mainly melanocytes, so that they cannot normally differentiate, grow and mature, resulting in a significant decrease in the density of mature pigment cells, mainly melanocytes, in fish skin and scales. The result is albinism or yellow body color in cultured fish. As for prevention and control countermeasures, the main approach is still proactive prevention. For cultured fish species whose body color is prone to change, such as yellow catfish, African catfish, Wuchang fish, black carp, etc., when formulating feed formulas, try not to use already oxidized oil raw materials such as corn oil, rice bran oil, low-quality phospholipid oil (phospholipid powder), oxidized fish oil, as well as corn DDGS with relatively high corn oil content, corn citric acid residue, and oxidized rice bran, etc. Oils and fats such as lard, soybean oil, rapeseed oil and beef tallow can be selected for inclusion in feed formulas.
The main hazards of melamine to cultured animals are mainly shown in the following aspects: ① It causes organic damage to the main internal organs of the fish body, resulting in organic pathological reactions, such as enlargement and hemorrhage of the hepatopancreas, kidney, spleen, etc. Due to damage to the main internal organ tissues, it may cause damage to the overall physiological function of the fish body, causing severe pathological reactions in the overall immunity and defense ability of the fish body, decreased growth rate, increased mortality, etc. ② Body color changes. At present, in most scaleless fish such as channel catfish, yellow catfish, catfish, and scaled fish such as Wuchang fish and black carp, the body color shows significant "albinism", and in severe cases the muscle color also changes. ③
Severe hemorrhage occurs in the digestive tract, gills, base of fin rays, epidermis, etc. ④ The production performance of cultured fish is seriously affected. For example, some enterprises have found that the culture effect of using feed containing fishmeal is not as good as that of feed without fishmeal, and high-protein, high-price feed is not as good as low-protein, low-price feed. Such difficult-to-understand strange phenomena are caused by adulteration of high-protein raw materials such as fishmeal. At present, the types of protein feed ingredients found to be adulterated with melamine include fishmeal, meat (bone) meal, corn gluten meal, yeast feed, monosodium glutamate protein feed, corn DDGS, rapeseed meal, cottonseed meal, bacterial protein feed, etc. As for biochemical fishmeal, protein essence, biological protein essence, etc., their essence is actually made with melamine as the main raw material. If feed enterprises find that the body color of fish changes severely after using their own feed products, they must first check the feed ingredients used, especially protein ingredients, mainly by measuring the content of 17 amino acids and calculating that the total amount of 17 amino acids must be greater than 90% of the crude protein mass. If it is only about 80%, it can be considered that the ingredient is adulterated with melamine-type non-protein nitrogen. After removing feed ingredients containing melamine-type non-protein nitrogen from the feed formula, and using bile acid products (such as Samp Keilikang), vitamin C phosphate and other products for rapid detoxification, relying on the recovery of the fish's own physiological health, the fish body color can recover in about 1 month.
(5) Impact of extruded feed on the body color of yellow catfish
In the population of yellow catfish cultured with extruded feed, generally 10-20% of yellow catfish will show abnormal melanin occurrence. Therefore, comprehensive analysis shows that the extrusion processing of feed in this city has a relatively obvious impact on feed substances and affects ⑵ at about 5 atmospheres. One possible reason is that vitamins are destroyed during extrusion processing, resulting in insufficient vitamins in the finished feed and affecting the body color of some fish. It is required to increase the amount of vitamin premix used when formulating extruded feed. The impact of extrusion processing on other feed substances still needs to be studied.
3. Body color protection of yellow catfish and the color-enhancing effect of feed pigments on yellow catfish
(1) Body color protection of yellow catfish
Like other fish, the formation of body color in yellow catfish is a complex process. Under artificial culture conditions, changes in body color can reflect the quality and safety of the feed. It can be considered that the change in body color of yellow catfish is essentially the result of the overall physiological function of the fish being affected to varying degrees. Therefore, in the process of formulating artificial compound feed, feed processing and use, in addition to the conventional attention to feed nutritional level and completeness of nutrients, attention should also be paid to feed safety issues. The former mainly affects the normal growth rate and feed efficiency of cultured fish, while the latter will have a major impact on the maintenance of the physiological function and health of cultured fish. Through feed nutrition and safety, ensure the health of cultured fish. The health of cultured fish ensures growth rate and normal physiological function, protects the normal body color of the fish and normal disease resistance and stress resistance. This should be the basic concept and basic technical countermeasure for protecting the normal body color of fish. At present, the main unsafe factors affecting feed safety come from oil oxidation and adulterated substances in feed ingredients. The protection of the normal physiological function of melanocytes must start from the protection of the overall physiological function of the fish, such as ensuring reasonable nutrient types and nutritional levels, and eliminating residues of toxic and harmful substances in compound feed; protecting the normal yellow body color of fish should ensure an appropriate quality level in compound feed, appropriate pigment types in feed, and effective pigment content.
(2) Color-enhancing effect of feed pigments on yellow catfish
The body color of fish can be controlled through the selection and use of feed pigments. Through our experiments and experience summarized in actual production, adding an appropriate amount of lutein (such as Jinhuangsu and Jinjuhuang) to feed has an ideal coloring effect on yellow catfish, while astaxanthin has an unsatisfactory color-enhancing effect on yellow catfish.
As shown in the figure, ensuring about 5% total fat in the feed and adding 100 mg/T lutein has a relatively ideal effect on the body color of yellow catfish after about 60 days of culture, very close to the natural body color of yellow catfish. Among them, lutein mainly comes from products extracted from marigold and corn lutein in corn gluten meal. If about 3% corn gluten meal is maintained in the compound feed, a relatively ideal culture effect can also be achieved. However, corn gluten meal is often found to be adulterated with melamine to increase crude protein content, so when selecting corn gluten meal, quality identification and inspection work must be strengthened. If the quality of corn gluten meal is difficult to guarantee, it is better not to use corn gluten meal and instead choose lutein-type pigment additives.
The culture result of using 100 mg/T astaxanthin in feed shows that the color-enhancing effect on the body color of yellow catfish is not ideal. In addition, the market price of astaxanthin is higher than that of lutein-type products. Therefore, astaxanthin may not be selected when enhancing the color of yellow catfish.
--------------------------------------
Try stopping the water or turning it down, have the fish in other ponds changed color?
--------------------------------------
Following with interest
I really had not noticed this phenomenon before
--------------------------------------
Is it a common phenomenon or individual cases?
Also, should we try changing the feed? Hehe
--------------------------------------
Customers with non-flowing-water culture have all turned yellow, while those with flowing-water culture have not changed color. Fat is definitely added sufficiently, and the quality of raw materials can also be guaranteed. What a strange phenomenon
--------------------------------------
Leaching loss?
Pond culture will be a bit better
--------------------------------------
Is it because yellow catfish consume a lot of energy in flowing water, the fat added to the feed is not enough, and pigment deposition is poor?
Yellow catfish (Pelteobagrus fulvidraco) belongs to the order Siluriformes, family Bagridae, genus Pelteobagrus Bleeker, commonly known as ga fish, yellow aunt, yellow-fin fish, etc., and is widely distributed in rivers, lakes, ditches and other waters in China. Yellow catfish has a bright body color, tender meat and rich nutrition. It is a high-quality and precious economic fish, and has now become one of the species that can achieve relatively good economic benefits in artificial culture. In natural water bodies, because yellow catfish feed on a large amount of algae and plankton rich in carotenoids, their body color is relatively bright. Under normal conditions, there are black spots on the sides of the body, and the rest is yellow. Under artificial culture conditions, the main problem that appears is the change in body color, and because of the change in body color, the commercial value is seriously affected. In addition to factors affecting body color such as water environment conditions and disease, the most important cause of body color change in yellow catfish is the major impact of feed substances on its body color. In fact, the impact of feed substances on fish body color only reflects the impact of feed substances on the overall physiological function of the fish. Based on the results in actual production and under experimental research conditions, this article analyzes the main types of body color changes in yellow catfish and their correlation with feed substances, hoping to provide technical reference for the formulation, production and use of compound feed for yellow catfish.
1. Species characteristics and body color of the genus Pelteobagrus
There are 5 species in the genus Pelteobagrus. The characteristics of each species are respectively yellow catfish (P. fulvidraco), intermediate yellow catfish (P. intermedius), long-barbel (fork-tailed) yellow catfish (P. eupogon), Vachelli's (river) yellow catfish (P. vachelli) and glossy yellow catfish (P. nitidus). Different species have different body shapes and body colors. Some species have relatively bright coloration, while others are relatively
pale. The species mainly cultured artificially are yellow catfish and Vachelli's yellow catfish, with other species mixed in in small amounts. Therefore, when the cultured species are different, the body shape and body color of the fish will be very different. Under artificial culture conditions, if everyone hopes to achieve the body shape and body color of yellow catfish (P. fulvidraco), it cannot be realized. It is only possible to achieve the body shape and body color that the species should have in the natural environment according to the respective body shape and body color of different species.
2. Body color changes of yellow catfish under culture conditions and their relationship with feed
(1) Yellow catfish cultured in large water bodies
Large water body culture mainly refers to yellow catfish stocked in lakes and reservoirs, without feeding compound feed. The fish feed in the natural environment, and the main food includes aquatic insects and their larvae, small shrimp, mollusks and small fish, etc. Therefore, the fish body color is the natural body color, as shown in Figure 2, and the body color is relatively bright.
(2) Yellow catfish lacking yellow pigment
Yellow catfish cultured with feed have relatively normal black body color, but lack yellow body color; there are
relatively obvious black patches, but the skin color is relatively light, and no yellow body color appears (see Figure 3).
The black body color of fish mainly depends on the number and distribution density of melanocytes in the skin, as well as the distribution state of melanosomes in melanocytes. The yellow body color mainly depends on carotenoids absorbed by the fish from the feed, such as the deposition state of lutein in the skin. This type of pigment is fat-soluble and is absorbed, transported and deposited along with feed fat. Therefore, when the body color of yellow catfish appears as shown in Figure 3, it indicates that the nutritional level of the feed is insufficient, or the feed lacks carotenoids that can be absorbed and deposited. As long as corresponding adjustments are made, the body color of yellow catfish can return to normal.
(3) Yellow catfish with yellow body color
As shown in Figure 4, the black spots on the fish body basically disappear, but the yellow body color is relatively obvious. The reason for this phenomenon is the combined result of a decrease in the number and distribution density of mature melanocytes in the skin and the deposition of yellow pigments such as lutein and carotenoids in the skin and muscle. When the number and distribution density of mature melanocytes in the fish skin decrease, if there are relatively large amounts of lutein and carotenoids absorbed and deposited along with fat, the fish body will show a yellow body color.
Like the pigment cells of fish and other vertebrates, new pigment cells do not proliferate through cell division. Instead, neural crest cells migrate to the skin, eyes, etc., differentiate into prepigment cells, and then the prepigment cells differentiate to form young melanocytes, xanthophores and other pigment cells, and the young pigment cells then develop into mature pigment cells. Taking melanocytes as an example, neural crest cells migrate to the skin and eyes, etc., differentiate into premelanocytes, and then the premelanocytes differentiate into melanoblasts. The melanoblasts gradually grow and develop into mature melanocytes. Therefore, the formation of a mature melanocyte must go through several stages, including the migration of neural crest cells, differentiation of premelanocytes, development of melanoblasts, and growth of melanoblasts. During this period, it is regulated and controlled by various hormones and physiological factors. If a physiological error occurs in any link during this period, it will affect the migration, differentiation, growth and development of melanocytes, and lead to a decrease in the number and distribution density of mature melanocytes in the skin, thereby affecting the fish body. In addition to being affected by factors such as the culture environment and disease, it is also affected by feed factors.
Therefore, when this body color appears, it should be the result of feed substances seriously affecting the formation of mature melanocytes and relatively high absorption of carotenoids, indicating that the feed contains substances that can affect the normal physiological function of the fish, such as containing relatively large amounts of oxidized oil, containing melamine-type non-protein nitrogen, insufficient vitamins, etc. The quality of the feed formula and feed ingredients should be checked, and technical measures such as eliminating harmful feed substances and ensuring sufficient vitamins should be adopted.
(4) Yellow catfish with severely affected body color
As shown in Figure 5, the body color of yellow catfish shows severe changes. Both the black and yellow body colors of the fish are seriously insufficient, and the fish body shows albinism. This is the result of toxic and harmful substances in the feed causing severe damage to the physiological function of the fish. Based on the current situation analysis, the direct cause is that the feed ingredients contain melamine-type non-protein nitrogen, or relatively high doses of oxidized oil were used.
Any feed substance that can cause major changes in the physiological function of the fish will cause disorder of the overall physiological function of the fish, and further seriously affect the normal migration, differentiation, development and maturation process of fish pigment cells, and cause changes in fish body color. This kind of fish body color change shows a strong correlation with feed quality and the feed of different feed enterprises. Only after finding and removing this substance that causes major changes in fish physiological function, and after the physiological function of the fish gradually recovers, can the recovery of fish body color and the maintenance of normal body color be ensured. This should be the basic technical countermeasure for solving fish body color changes caused by feed substances.
From the analysis of the breadth and severity of the impact of feed substances on fish physiological function, at the current stage the main feed substances are mainly oxidized oils in feed and non-protein nitrogen such as melamine mixed into feed ingredients, followed by vitamins, minerals, especially some trace elements.
The impact of oxidized oils in feed on fish body color includes two aspects. First, after oxidized oils enter the fish body, they may continue to oxidize and produce relatively large amounts of oxygen free radicals or other free radicals. These free radicals can cause oxidation and breakage of unsaturated bonds in carotenoid molecules, causing carotenoid pigment substances to lose their pigment function and leading to degradation of fish body color. On the other hand, the impact of oxidized oils in feed on the physiological function of cultured fish can seriously affect pigment cells, mainly melanocytes, so that they cannot normally differentiate, grow and mature, resulting in a significant decrease in the density of mature pigment cells, mainly melanocytes, in fish skin and scales. The result is albinism or yellow body color in cultured fish. As for prevention and control countermeasures, the main approach is still proactive prevention. For cultured fish species whose body color is prone to change, such as yellow catfish, African catfish, Wuchang fish, black carp, etc., when formulating feed formulas, try not to use already oxidized oil raw materials such as corn oil, rice bran oil, low-quality phospholipid oil (phospholipid powder), oxidized fish oil, as well as corn DDGS with relatively high corn oil content, corn citric acid residue, and oxidized rice bran, etc. Oils and fats such as lard, soybean oil, rapeseed oil and beef tallow can be selected for inclusion in feed formulas.
The main hazards of melamine to cultured animals are mainly shown in the following aspects: ① It causes organic damage to the main internal organs of the fish body, resulting in organic pathological reactions, such as enlargement and hemorrhage of the hepatopancreas, kidney, spleen, etc. Due to damage to the main internal organ tissues, it may cause damage to the overall physiological function of the fish body, causing severe pathological reactions in the overall immunity and defense ability of the fish body, decreased growth rate, increased mortality, etc. ② Body color changes. At present, in most scaleless fish such as channel catfish, yellow catfish, catfish, and scaled fish such as Wuchang fish and black carp, the body color shows significant "albinism", and in severe cases the muscle color also changes. ③
Severe hemorrhage occurs in the digestive tract, gills, base of fin rays, epidermis, etc. ④ The production performance of cultured fish is seriously affected. For example, some enterprises have found that the culture effect of using feed containing fishmeal is not as good as that of feed without fishmeal, and high-protein, high-price feed is not as good as low-protein, low-price feed. Such difficult-to-understand strange phenomena are caused by adulteration of high-protein raw materials such as fishmeal. At present, the types of protein feed ingredients found to be adulterated with melamine include fishmeal, meat (bone) meal, corn gluten meal, yeast feed, monosodium glutamate protein feed, corn DDGS, rapeseed meal, cottonseed meal, bacterial protein feed, etc. As for biochemical fishmeal, protein essence, biological protein essence, etc., their essence is actually made with melamine as the main raw material. If feed enterprises find that the body color of fish changes severely after using their own feed products, they must first check the feed ingredients used, especially protein ingredients, mainly by measuring the content of 17 amino acids and calculating that the total amount of 17 amino acids must be greater than 90% of the crude protein mass. If it is only about 80%, it can be considered that the ingredient is adulterated with melamine-type non-protein nitrogen. After removing feed ingredients containing melamine-type non-protein nitrogen from the feed formula, and using bile acid products (such as Samp Keilikang), vitamin C phosphate and other products for rapid detoxification, relying on the recovery of the fish's own physiological health, the fish body color can recover in about 1 month.
(5) Impact of extruded feed on the body color of yellow catfish
In the population of yellow catfish cultured with extruded feed, generally 10-20% of yellow catfish will show abnormal melanin occurrence. Therefore, comprehensive analysis shows that the extrusion processing of feed in this city has a relatively obvious impact on feed substances and affects ⑵ at about 5 atmospheres. One possible reason is that vitamins are destroyed during extrusion processing, resulting in insufficient vitamins in the finished feed and affecting the body color of some fish. It is required to increase the amount of vitamin premix used when formulating extruded feed. The impact of extrusion processing on other feed substances still needs to be studied.
3. Body color protection of yellow catfish and the color-enhancing effect of feed pigments on yellow catfish
(1) Body color protection of yellow catfish
Like other fish, the formation of body color in yellow catfish is a complex process. Under artificial culture conditions, changes in body color can reflect the quality and safety of the feed. It can be considered that the change in body color of yellow catfish is essentially the result of the overall physiological function of the fish being affected to varying degrees. Therefore, in the process of formulating artificial compound feed, feed processing and use, in addition to the conventional attention to feed nutritional level and completeness of nutrients, attention should also be paid to feed safety issues. The former mainly affects the normal growth rate and feed efficiency of cultured fish, while the latter will have a major impact on the maintenance of the physiological function and health of cultured fish. Through feed nutrition and safety, ensure the health of cultured fish. The health of cultured fish ensures growth rate and normal physiological function, protects the normal body color of the fish and normal disease resistance and stress resistance. This should be the basic concept and basic technical countermeasure for protecting the normal body color of fish. At present, the main unsafe factors affecting feed safety come from oil oxidation and adulterated substances in feed ingredients. The protection of the normal physiological function of melanocytes must start from the protection of the overall physiological function of the fish, such as ensuring reasonable nutrient types and nutritional levels, and eliminating residues of toxic and harmful substances in compound feed; protecting the normal yellow body color of fish should ensure an appropriate quality level in compound feed, appropriate pigment types in feed, and effective pigment content.
(2) Color-enhancing effect of feed pigments on yellow catfish
The body color of fish can be controlled through the selection and use of feed pigments. Through our experiments and experience summarized in actual production, adding an appropriate amount of lutein (such as Jinhuangsu and Jinjuhuang) to feed has an ideal coloring effect on yellow catfish, while astaxanthin has an unsatisfactory color-enhancing effect on yellow catfish.
As shown in the figure, ensuring about 5% total fat in the feed and adding 100 mg/T lutein has a relatively ideal effect on the body color of yellow catfish after about 60 days of culture, very close to the natural body color of yellow catfish. Among them, lutein mainly comes from products extracted from marigold and corn lutein in corn gluten meal. If about 3% corn gluten meal is maintained in the compound feed, a relatively ideal culture effect can also be achieved. However, corn gluten meal is often found to be adulterated with melamine to increase crude protein content, so when selecting corn gluten meal, quality identification and inspection work must be strengthened. If the quality of corn gluten meal is difficult to guarantee, it is better not to use corn gluten meal and instead choose lutein-type pigment additives.
The culture result of using 100 mg/T astaxanthin in feed shows that the color-enhancing effect on the body color of yellow catfish is not ideal. In addition, the market price of astaxanthin is higher than that of lutein-type products. Therefore, astaxanthin may not be selected when enhancing the color of yellow catfish.
--------------------------------------
Try stopping the water or turning it down, have the fish in other ponds changed color?
--------------------------------------
Following with interest
I really had not noticed this phenomenon before
--------------------------------------
Is it a common phenomenon or individual cases?
Also, should we try changing the feed? Hehe
--------------------------------------
Customers with non-flowing-water culture have all turned yellow, while those with flowing-water culture have not changed color. Fat is definitely added sufficiently, and the quality of raw materials can also be guaranteed. What a strange phenomenon
--------------------------------------
Leaching loss?
Pond culture will be a bit better