Wen 丨 Yujie History Museum
Editor丨Yujie History Museum
The mainland has vast coastal and inland waters, rich in aquatic resources, among which the large yellow croaker is favored as a unique marine economic fish, and is loved by consumers for its delicious meat quality and high nutritional value.
Before the 70s of the 20th century, the demand for large yellow croaker continued to grow, and the annual catch of wild large yellow croaker reached nearly 100,000 tons, which was one of the main targets of continental marine fishing.
Due to the serious damage caused by overfishing to the marine ecological environment, wild yellow croaker resources have been drastically reduced, so artificial cultivation has become an important way to meet market demand.
Compared with wild large yellow croaker, farmed large yellow croaker usually has problems such as light body color, higher fat content, stronger fishy smell, lower content of taste substances and unsaturated fatty acids, which seriously affects the commercial value of farmed large yellow croaker.
How to improve the quality of farmed large yellow croaker has become one of the key issues for the healthy development of the industry, and the methods used to improve the quality of farmed fish mainly include genetic selection, optimization of breeding environment and regulation of feed nutrition, among which feed nutrition regulation is considered to be a safe and effective improvement method.
So next, let's follow Yujie to see how feed additives improve the growth performance and quality of juvenile fish in large yellow croaker farming.
Feed additives
Feed additives occupy an important position in the aquaculture industry, they are a class of substances that are added in small amounts but have significant effects.
According to their functional differentiation, feed additives are usually divided into two main categories in the market: nutritional additives and non-nutritional additives.
With the rapid expansion of the scale of large yellow croaker farming, the demand for feed additives is increasing, and it is worth noting that with the increase of aquaculture scale, high-density and intensive farming models also bring a series of challenges.
This model not only increases the purification burden of aquaculture water, but also leads to the improper use of drugs, including antibiotics and antimicrobials, which can lead to the growth of resistant bacteria and the problem of drug residues in fish, seriously threatening the health of consumers.
Therefore, the search for safe and environmentally friendly feed additives to improve the quality of farmed large yellow croaker has become a future development trend.
The role of nutritional additives in feed is very important, mainly including amino acids, fatty acids, carotenoids and vitamins, etc., these additives have a significant impact on the growth and quality improvement of large yellow croaker.
Amino acids are the basic components of the protein needed by fish, which is essential for maintaining the normal physiological function of fish, and the essential amino acids of fish include arginine, histidine, etc., a total of 10 kinds, some of which can effectively improve the texture of large yellow croaker meat.
Studies have also shown that the addition of hydroxyproline can significantly increase the crude protein content in the meat of large yellow croaker, and significantly improve the hardness, elasticity and chewiness of the fish.
In addition, the addition of astaxanthin and lutein also has an effect on the body color of large yellow croaker. The experimental results showed that lutein could effectively increase the yellow value of the back and abdomen of large yellow croaker, while the addition of astaxanthin would cause the back and abdomen of large yellow croaker to turn red.
Finally, the interaction between vitamin C and proline also has an important effect on the flesh quality and antioxidant properties of large yellow croaker.
Studies have found that vitamin C and proline have a synergistic effect, which can significantly improve the firmness and collagen content of fish, while improving the antioxidant capacity of muscles.
So, what about non-nutritive additives?
Application of non-nutritive additives
Non-nutritive additives play an important role in feed, including Chinese herbal additives, microbial additives and feed enzymes, which are mainly used to promote growth and development, improve feed efficiency and prevent fish diseases.
Recent studies have also shown that some herbal additives have potential benefits for improving muscle quality in farmed large yellow croaker.
The composition of Chinese herbal additives is quite complex, including glycosides, organic acids, alkaloids, flavonoids, polysaccharides and tannins and other active ingredients, usually with antioxidant, anti-inflammatory, bacteriostatic and other pharmacological activities, and their toxic side effects are relatively small.
For example, ginseng extract can significantly increase the amount of crude protein and crude fat in the muscles of large yellow croaker while increasing the total glycine, lysine, and amino acids.
In addition, the addition of ginseng extract can also increase the content of n-3 fatty acids in muscles, which help to expand blood vessels and lower blood pressure, similar to hormones, while reducing the content of n-6 fatty acids can help reduce inflammation and benefit human health.
The mainland is rich in bamboo resources, and the secondary metabolites extracted from different parts of bamboo exhibit multiple pharmacological activities and are suitable for food additives as potential natural sources.
These non-nutritive additives play an important role in the aquaculture industry, not only contributing to the growth and health of fish, but also improving feed efficiency and improving the muscle mass of farmed large yellow croaker.
These findings provide valuable information for the aquaculture industry and are expected to be more widely used in the future.
So, what impact will the use of nutrients in bait have on the growth of juvenile fish?
Effects of feed on the growth of juvenile fish
The body color of fish undergoes changes at different stages of growth, development and reproduction, and the final body color formation is regulated by a series of genes related to body color.
In recent years, studies using zebrafish models have identified the effects of multiple genes on body color in fish by comparing the differences between wild-type and body color mutants.
The pigment cells of fish are mainly divided into four types, including melanocytes, yellow pigment cells, red pigment cells and iridescent cells, and the type and amount of pigment in these pigment cells play a decisive role in the body color of fish.
Further studies found that genes associated with melanin synthesis included Tyr, Dct, and Gch.
The genes of Kita, Ednrb, Csflr and Mclr encode membrane receptor proteins, which affect the early and late survival of fish melanocytes, the late survival of iridescent cells, the differentiation and survival of yellow blood cells, and the synthesis and regulation of melanin.
In addition to melanin, fish cannot synthesize other pigments in the body and must be ingested from feed and obtained by metabolism and transformation in the body.
Common feed colorants include astaxanthin, progesterone, zeaxanthin, and canthaxanthin, and some of the carotenoids ingested by fish are converted into vitamin A, while the rest is deposited on the muscles and body surface, changing the muscle texture and body color of the fish.
The fat content and n-3 polyunsaturated fatty acid content in the feed and the ratio between them also affect the formation of body color in fish, possibly because the low fat content reduces the utilization of carotenoids by fish.
One study determined that the minimum feed fat content required for body color of large yellow croaker was 12%.
In addition, the vitamins and minerals in the feed also affect the formation of fish body color by participating in the normal metabolism of the body.
Insufficient vitamin A in feed may cause carotenoids to be converted to vitamin A in the intestines of fish, reducing body color coloration.
On the other hand, increasing the content of vitamin E in the feed is beneficial to reduce the consumption of carotenoids as antioxidants, thereby improving the coloring effect of fish body color.
Nutritional additives include amino acids, fatty acids, carotenoids, vitamins, etc., which play an important role in the growth and quality improvement of large yellow croaker.
For example, the addition of hydroxyproline can improve meat hardness and collagen content, the addition of conjugated linoleic acid can improve the content of amino acids and inosinic acid in fish umami, and vitamin C and proline work synergistically to improve fish hardness and antioxidant capacity.
Non-nutritive additives include Chinese herbal medicines, microbial additives and feed enzymes that promote growth, improve feed efficiency and prevent fish diseases.
Some Chinese herbal additives have been shown to have beneficial effects on the meat quality of farmed yellow croaker, such as the addition of ginseng extract and bamboo cyanin, which have played a positive role in improving muscle quality and increasing the commercial value of large yellow croaker.
Finally, the study also showed that the body color and quality of farmed large yellow croaker are closely related to the nutritional composition of feed, including carotenoids, fat content, vitamins and minerals, etc., and appropriate adjustment of the proportion of these components in feed can improve the body color and meat quality of large yellow croaker.
Feed additives play an important role in improving the quality of farmed large yellow croaker, providing a valuable tool for the aquaculture industry and is expected to promote the healthy development of this industry.