Nutritional Value Assessment of Aquatic Complex Protein Products: Effects of Amino Acid Composition, Digestibility, and Animal Growth in Aquaculture

Aquatic complex protein products (such as plant protein+animal protein, microbial protein complex products) are important protein sources that replace traditional fish meal, and their nutritional value directly determines the aquaculture effect. The evaluation revolves around three dimensions: whether the amino acid composition is suitable, whether the digestion rate meets the standard, and whether it can promote animal growth. The key logic will be broken down in plain language below.

1、 Amino acid composition: looking at "comprehensiveness" and "balance" to match the needs of aquatic animals

Amino acids are the basis for the synthesis of muscles and enzymes in aquatic animals, and the core advantage of composite proteins is to compensate for the amino acid deficiencies of a single protein source through compounding, making nutrition more comprehensive. When evaluating, focus on two points:

1. Are essential amino acids "complete"

Aquatic animals (such as fish and shrimp) cannot synthesize essential amino acids (such as lysine, methionine, and threonine) on their own and must obtain them from feed. Lack of one of them will affect their growth.

Single plant protein (such as soybean meal) often lacks methionine, single animal protein (such as meat and bone meal) may lack lysine, while composite protein can fill these gaps through combinations such as "soybean meal+fish meal" and "soybean meal+yeast protein";

High quality composite protein should contain more than 10 essential amino acids, and each content should not be lower than the lower limit of aquatic animal requirements (such as grass carp requiring about 1.8% lysine and 0.6% methionine).

2. Does the amino acid pattern "match"

Even if the essential amino acids are complete, a mismatch in proportion can still waste nutrients (such as an excess of certain amino acids being excreted with feces).

When evaluating, it is necessary to compare the "composite protein amino acid ratio" with the "target aquaculture animal demand ratio" (such as shrimp farming requiring high lysine and fish farming requiring high methionine);

If the proportion deviation is large, it can be adjusted by adding a small amount of monomeric amino acids (such as methionine additives) to make the overall pattern more suitable.

2、 Digestive rate: Look at "absorption efficiency" to avoid nutrients being "eaten but not utilized"

The digestibility of complex proteins directly affects the cost of aquaculture - low digestibility, animals eating too much, growing slowly, and also polluting water quality. The evaluation focuses on two key indicators:

1. Protein digestibility: core measurement indicator

The proportion of protein that aquatic animals can absorb and utilize in the total protein in feed generally needs to reach 80% or more (high-quality products can exceed 85%).

Reasons for low digestibility: improper processing of protein sources (such as excessive heating of soybean meal, protein denaturation), high fiber content (such as excessive crude fiber in some plant protein raw materials, difficult for animals to digest);

How to choose: Prioritize selecting composite proteins labeled as "enzymatic hydrolysis process" or "micro fermentation process", which can destroy protein structure and improve digestion rate (such as enzymatic soybean meal protein digestion rate being 10% -15% higher than ordinary soybean meal).

2. Amino acid digestibility: more accurate evaluation

More refined than protein digestion rate, it can determine the absorption of each amino acid (such as a complex protein with high overall digestion rate but low methionine digestion rate, which still affects growth).

When evaluating, the focus should be on the digestibility of essential amino acids, especially lysine and methionine, ensuring that both have a digestibility rate of not less than 80%;

If the digestion rate of a certain essential amino acid is low, it is necessary to check whether the raw materials have deteriorated (such as fish meal oxidation reducing methionine digestion rate) or whether the compounding ratio is reasonable.

3、 The impact on the growth of farmed animals: looking at the "actual effect" and verifying its value with data

Laboratory data (amino acids, digestibility) need to be validated through aquaculture practice, with a focus on three growth indicators as the "ultimate criteria" for evaluating nutritional value:

1. Growth rate: Look at the "weight gain rate"

Comparing the weight gain of farmed animals using composite proteins with traditional proteins such as fish meal, high-quality composite proteins should be able to achieve or approach the effects of traditional proteins.

Example: When raising California bass, using a "soybean meal+yeast protein" composite protein feed, if the weight gain rate of the fish within 8 weeks is not more than 5% lower than using pure fish meal feed, it indicates that its nutritional value meets the standard;

If there is a significant difference in weight gain rate (such as a decrease of more than 10%), it may be due to amino acid mismatch or low digestibility, and the product formula needs to be adjusted.

2. Survival rate: looking at the "disease resistance correlation"

High quality composite protein can enhance animal immunity and reduce the risk of disease and death by providing balanced nutrition.

Observation during evaluation: whether animals frequently experience enteritis and gill rot. Insufficient nutrition can lead to a decrease in disease resistance;

If the survival rate is more than 3% lower than using traditional feed, it is necessary to check whether the composite protein lacks key nutrients (such as vitamins and minerals, which may be omitted in some low-priced products).

3. Feed coefficient: looking at "cost-effectiveness"

The lower the coefficient, the lower the cost (the coefficient of high-quality compound protein feed can be controlled within 1.2-1.5, while inferior products may exceed 1.8).

The reasons for high feed efficiency are: low digestibility (high nutrient waste), amino acid imbalance (high animal metabolic consumption);

Calculation logic: If composite protein feed is 20% cheaper than traditional fish meal feed and the feed coefficient is only 5% higher, then the overall cost is lower and the cost-effectiveness is higher.

4、 Summary: The Core Logic of Evaluation

The nutritional value assessment of aquatic composite protein products should follow a dual standard of "laboratory data+practical verification": first, check whether the amino acids are "complete and balanced", then check whether the digestion rate is "high and stable", and finally verify the actual effect with growth rate, survival rate, and feed coefficient. The key to choosing the right product is not to blindly look at the price, but to combine it with the needs of the target breeding animals, match products with excellent amino acid patterns, high digestion rates, and good practical effects, in order to reduce costs while ensuring breeding efficiency.