Researchers from the State University of Ponta Grossa, the State University of Maringá, and the Texas A&M University System published a scientific review consolidating information on the amino acid requirements of Nile tilapia (Oreochromis niloticus).
They also report that the expansion of precision amino acid nutrition diets for tilapia is receiving more attention due to the demand for flexibility in widespread ingredient substitutions that will allow compliance with environmentally sustainable principles.
Tilapia Amino Acid Requirements
Many relevant results on the amino acid requirements of tilapia have been published in recent years; however, these have not been updated in the regulatory entities for more than a decade.
Variables such as fish variety and size, feed composition and processing technology, as well as feed management and statistical methods, can influence experimental estimates of tilapia amino acid requirements.
The amino acid composition in tilapia tissues
The amino acid composition of Nile tilapia eggs and body at different stages of production include lysine as the dominant amino acid, while glutamic acid is the main non-essential amino acid.
However, the researchers describe, there is little information on the impact of amino acid supplementation of the diet on the amino acid profiles of eggs and tissues.
Some research has identified that the amino acid composition of eggs varies with the protein in the diet. In contrast, early studies have reported that dietary amino acid supplementation does not alter the whole-body amino acid composition of Nile tilapia at weaning, pre-growth, and grow-out.
Amino acid recommendations for tilapia
Tilapia amino acid requirements were published by the National Research Council (NRC) in 2011. However, genetic improvements and higher performance targets set by the tilapia industry have prompted researchers to revise the recommendations.
According to the researchers, previous studies have shown that the culture system influences the protein requirements in the diet of Nile tilapia broodstock. The study includes amino acid inclusion recommendations for broodstock.
The concept of the ideal protein for pets was proposed by Mitchell 60 years ago. The concept of ideal protein refers to a level of protein in the diet with an amino acid profile that exactly meets the requirements of the animal.
Lysine
Lysine is the first limiting essential amino acid in diets based on maize, wheat, and cereal co-products, and lysine supplementation has been adopted in practical and experimental diets for tilapia.
“Previous studies indicate that lysine utilization efficiency remained relatively high (+63%) in hatchery and pre-grown Nile tilapia, and decreases (48%) in tilapia grow-out,” they report.
In this sense, it has been established in:
- Hatchery: 2.7 mg of lysine/kg of tilapia body.
- Pre-growing: 45.1 mg of lysine/kg of tilapia body.
- Growing 56.3 mg of lysine (kg of tilapia body.
In addition, the study authors cite that previous studies determined that growing Nile tilapia required an intake of 23 mg of lysine to deposit 1 g of body weight gain.
According to the researchers, lysine improves body weight, feed efficiency and fillet performance in Nile tilapia.
Regarding tilapia raised in brackish water (8‰), it requires 23 g/kilogram of diet.
Sulfur-containing amino acids
Methionine and cysteine are the total sulfur-containing amino acids and are considered in tilapia diets. It is important to note that methionine is considered the first limiting amino acid in cereal-based tilapia feeds.
The optimal methionine + cysteine requirement has been established with an average of 9.7 g/kg of diet (3.5% crude protein).
Threonine
Threonine is a potentially limiting amino acid in conventional diets for tilapia based on corn, wheat, soybeans and co-products.
The optimal threonine requirement is well established in the literature and averages 12 g/lg of diet (4.3% crude protein). Studies have established that an intake of 15.9 mg of threonine is required to deposit 1 g of body weight.
Tryptophan
Tryptophan is considered a potential limiting amino acid in conventional plant-based tilapia diets, particularly maize. In this review, the tryptophan requirement averages 3.1 g/kg diet (1% crude protein).
Previous studies established that pre-growing Nile tilapia require an intake of ~3 mg tryptophan to deposit 1 g of protein in the tilapia body.
Branched-chain amino acids
Isoleucine, leucine, and valine are branched-chain amino acids that attract less attention, as their requirements are generally met by typical protein feeds in conventional Nile tilapia diets.
According to the researchers, mounting evidence suggests that the optimal ratio of branched-chain AA (Ile:Leu:Val) is 1:1.3:0.9 in diets for Nile tilapia prior to grow-out.
Dietary requirements for isoleucine, leucine, and valine average 10.5 g/kg diet (3.8% crude protein), 11.8 g/kg diet (4.2% crude protein), and 10.1 g/kg diet (3.6% crude protein). ), respectively.
Arginine
It should be noted that the optimal requirement for arginine is well established in the literature and averages 14.8 g/kg of diet (5.1% crude protein).
Also of note, a previous study found that Nile tilapia fed 23.9 g arginine/kg diet exhibited higher immune responses and survival when challenged by Streptococcus agalactiae.
Histidine
Histidine is considered a marginally limiting amino acid in typical plant-based protein feeds used in Nile tilapia diets.
Dietary histidine requirements average 7.3 g/kg of diet (3.4 % crude protein), and previous studies reported that Nile tilapia require an intake of ~9 mg histidine to deposit 1 g of body weight.
Total aromatic amino acids
The dietary total aromatic amino acid (phenylalanine plus tyrosine) requirements of Nile tilapia have not been extensively explored by the academic community, possibly because both amino acids are not considered marginally limiting in feed ingredients typically used for tilapia.
The optimal requirement for phenylalanine plus tyrosine averaged 18.3 g/kg of diet (5.9 % crude protein). A recent study reported that Nile tilapia require an intake of ~35 mg phenylalanine plus tyrosine to deposit 1 g of body weight.
Non-essential amino acids
Growing scientific evidence suggests that non-essential amino acids are closely related to growth performance, health, and meat quality of Nile tilapia.
Non-essential amino acids assume more important roles in plant-rich fish diets due to their more limited presence.
Conclusion
“Emerging evidence indicates that not only essential but also some non-essential amino acids regulate growth performance, fillet yield, and meat quality, as well as reproductive performance, gut morphology, gut microbiota, and immune responses. ”, they conclude.
Reference (free access)
Furuya, Wilson Massamitu, Thais Pereira da Cruz, and Delbert Monroe Gatlin, III. 2023. “Amino Acid Requirements for Nile Tilapia: An Update” Animals 13, no. 5: 900. https://doi.org/10.3390/ani13050900
