Due to its balanced amino acid, good palatability and high digestibility, fishmeal has always been the main protein source for aquatic feed, especially for carnivorous aquatic animal feed. However, due to the limited world fishmeal resources and the rapid growth of world aquaculture production, the application of alternative proteins has become a hot spot in aquatic animal nutrition research. Alam et al. 2004 believe that in addition to the anti-nutritional factors and palatability of prion protein, the balance of amino acids is the most important factor determining the nutritional value of feed protein. Takeshi et al. 2000 found through experiments that the balance of  amino acids has a greater impact on the growth performance of rainbow trout than the crude protein content. How to improve the amino acid balance of feed protein has become a research hotspot. The reasonable compatibility of feed protein source is one of the methods to solve this problem, and the addition of synthetic amino acid is undoubtedly the most direct solution. The application effect and use method of synthetic amino acids in aquafeeds have been controversial in academia. This paper reviews the research results of the application of synthetic amino acids in aquafeeds, with a view to providing reference for future research.
Application effect of synthetic amino acids in
There are many studies on the application of synthetic amino acids in aquatic animal feeds, but there are major differences in conclusions. Some scholars believe that the addition of synthetic amino acids can improve the imbalance of amino acids, promote the absorption and utilization of proteins, and thus promote the growth of aquatic animals. Eric et al. 2000 In the study of partial replacement of fishmeal with low-fat soybean meal, the addition of a variety of synthetic amino acids significantly improved the growth performance of American lobster. Floreto et al. 2000 reported that the addition of synthetic amino acids to soybean meal feeds can significantly improve the growth performance of American lobsters. Kim et al. (1991) added a restricted amino acid of methionine and arginine casein to a feed containing casein as a protein source to feed the feed group with 30% crude protein content of rainbow trout to achieve unadded amino acids and crude protein. The growth effect of the feed group with a content of 40%. Markus (2000) showed that the addition of lysine to rainbow trout feed at different crude protein levels promoted growth and increased protein deposition. Cheng et al. 2003 showed that the addition of synthetic lysine to plant-derived feed can significantly increase the growth rate of rainbow trout. Ian Forster et al. (1998) reported that with the addition of lysine, the growth rate and nitrogen deposition of Japanese larvae and larvae were significantly increased, and the amount of fat deposition decreased. Strorebakken et al. 2000 showed that the addition of synthetic amino acids to the Atlantic 鲑 soy protein concentrate diet can effectively reduce the feed-to-weight ratio and improve its growth performance. Williams et al. 2001 pointed out that carp can make better use of synthetic amino acids in feed. Not all studies have concluded that aquaculture animals can effectively use synthetic amino acids and even if they are against the same species, the conclusions are different. Pongmaneerat et al. (1993) showed that the addition of lysine, methionine and threonine to carp-free fishmeal feed did not help to increase the protein and energy deposition of the feed. Aoki et al. 2000 and Takagi et al. 2001 pointed out that  鲷 鲷 can not effectively use synthetic amino acids. Sveier et al. 2001 showed that the addition of L-Met to feed had no effect on the growth performance of Atlantic salmon. Similarly, there are similar reports on crustaceans. McConnell's 1987 study suggests that the addition of amino acids to Chinese shrimp feed will inhibit growth. Teshima et al. 2004 and Alam et al. 2004 and 2005 all proved that Japanese marsh shrimp could not make good use of synthetic amino acids. There are many reasons for the difference in the application of synthetic amino acids. One of the most important reasons is the lack of standards for amino acid requirements. Relative to the research on the amino acid requirements of aquatic animals in livestock and poultry, there are few reports on the demand for several restricted amino acids such as Lys, Met and Arg, and the conclusions are not uniform, lack of comprehensiveness and Systematic. Taking Nile tilapia as an example, the demand for lysine in the NRC 1993 standard is only 1.43  and the lysine requirement determined by the Nile tilapia muscle amino acid model is 1.66 . Furuya et al. 2004 Based on the muscle amino acid model of Nile tilapia, the amino acid level was balanced by adding methionine, lysine and threonine in the fishmeal-free feed, and the production effect was the same as that of the fishmeal group. As the production process of synthetic amino acids is gradually improved, the cost is gradually reduced. Research on the amino acid requirements of aquatic animals will be more helpful in promoting the application of synthetic amino acids in aquafeeds. By adding synthetic amino acids to feeds to achieve an ideal protein model, improve protein. The use of efficiency  to alleviate the current shortage of protein resources.
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