In order to satisfy protein synthesis and deposition, juvenile fish or fast-growing fish have a larger requirement for essential amino acids than adult fish or slow-growing fish. The study on the Lys demand of Atlantic salmon of different specifications has been carried out, and the results show that the demand of Lys for Atlantic salmon with initial body weights of 4.7g, 367g and 642g is 3.98%, 3.25%-3.65% and 5.04%, respectively ( % Crude protein), the possible reason is that the metabolism of juvenile fish is strong, which requires more essential amino acids for protein synthesis. In addition, differences in fish body enzyme activities at different growth stages may also affect the study of essential amino acid requirements.
Addition of essential amino acids in feed
Under normal circumstances, the absorption of protein amino acids in feed ingredients and free crystal amino acids added from outside sources is not synchronized by fish. For example, some studies believe that the utilization rate of protein-bound Lys in the feed is higher than crystalline Lys. The addition of crystalline amino acids to feed may affect the absorption of other essential amino acids and cause excessive amino acid catabolism. In addition, soaking the feed in water can easily cause the added crystalline amino acids to dissolve and lose. These factors will lead to the fish's demand for essential amino acids. Extruded fish feed pellet by fish feed production line https://www.zenopelletmachine.com/product/floating-fish-feed-production-line/ will reduce this kind of condition .
Adding coated amino acids can improve the low utilization rate of crystal amino acids in fish feed. When added coated amino acids, the dissolution rate of amino acids in water is reduced, and the utilization efficiency of amino acids by the fish body is significantly improved at the same time. Compared with no supplementation or supplementation of crystalline Lys in the feed, the growth, feed efficiency and protein synthesis rate of grass carp were improved. In addition, crystalline Lys and coated Lys were added to make pellet feed, and then a certain amount was used to determine the dissolution rate of Lys. The results showed that the dissolution rate of Lys in the crystalline amino acid feed group was about 13.22%, while the Lys in the coated amino acid feed group was about 13.22%. The dissolution rate is about 4.81%, which is significantly lower than the former.
Therefore, the added form of essential amino acids will also affect the study of fish requirements. When added in the form of crystalline amino acids, fish need more essential amino acids than when added in the form of enveloped amino acids.
The effect of feed protein level and energy concentration
When the protein level in the experimental feed exceeds the optimal requirement for the fish body, a part of the protein will be used to provide energy rather than for growth, thereby reducing the utilization efficiency of protein and amino acids, resulting in a high demand for the determined essential amino acids. When determining the requirement of essential amino acids, the feed protein level should be lower than the actual protein requirement, in order to maximize the utilization of other amino acids.
Feed energy level also affects the essential amino acid requirements of fish. There is a positive correlation between the requirement of essential amino acids and the energy level of the feed. There are also studies that believe that the feed energy level cannot be ignored when comparing the Arg requirements of different fishes. Some scholars have also begun to consider the impact of the energy level in the feed on the research results when studying the requirement of essential amino acids.