Date: 25/02/2019

In an animal husbandry system, efficient food management is a determining factor in the business success. In an production environment of aquatic organisms (aquiculture) it’s not different.

Proper balancing of diets for fish feeding requires studies about nutritional needs to maximize growth and reproduction.

By optimizing the ingredients used, it is possible to increase the performance of the farming, animal’s health and by reducing the emission of pollutants in the aquatic environment, the water quality of the nurseries is kept.

As a consequence of poor diet formulation, there are:

  • Decrease in animal performance;
  • Increase in feed costs;
  • Increase of creation time for slaughter;
  • Decrease in the profits of the activity;
  • Decrease in water quality.

Fish Flour and it's use

In aquaculture, the ingredient commonly used in diets is fish flour. This input is a commercial product made from fish, bones and processed fish offal.

It is a product derived from the cooking, drying and grinding of the ingredients and its final presentation consists of a brown colored powder. Despite the many researches already done, fishmeal remains one of the main components in the balance of diets in aquaculture.

However, fish-based feeds are known to vary greatly in composition, which makes standardization in relation to adequate balancing of diets hard and and they present high mineral content (sometimes more than 20%) and Phosphorus that has a high impact on the quality of water and the environment.

Sources of vegetable protein, such as soybean meal and corn, are good sources of protein to replace fishmeal. On the other hand, such nutrients may contain non nutritious substances (such as phytic acid), lower amino acid digestibility, high fiber content, and low availability of phosphorus .

Protein on diet

Among the nutrients to be supplied, the inclusion of protein is the most important in fish diets.  Proteins are defined as macromolecules formed by a sequence of peptides. Peptides are organic molecules which have in their structure two or more amino acids, linked from peptide bonds.

The amino acid sequence and the presence of essential amino acids are the characteristics that differ each protein and its biological values. Proteins containing the highest amount of essential amino acids are defined as proteins of higher biological value.

Therefore, the inclusion of high quality protein (high biological value) in fish feed is directly related to growth performance.

That is, the quality of the protein, defined by the amino acid profile that constitutes it and the quality of the protein source provided, is related to the profile of available and digestible essential amino acids.

Nutrient Digestibility 

The rate of nutrient digestibility is determined by the percentage of nutrient that is ingested and absorbed by the animal’s organism.

The amount of digestible protein is defined by the amount of protein ingested minus the amount of undigested and unabsorbed protein. The undigested and absorbed residue is eliminated through the faeces.  The digestion of nutrients starts as soon as the food is consumed.

This process happens by physical (chewing) and chemical means (enzymatic digestion). More complex nutrient chains undergo enzymatic hydrolysis processes, which will be addressed in the next topic.

Enzymatic Hydrolysis

Food enzymatic digestion in animals occurs from the presence of enzymes in saliva (eg amylase), stomach (pepsin present in gastric juice) and small intestine (peptidases present in enteric juice).

These enzymes exert a function of breaking (through hydrolysis) the more complex chains of nutrients. In the case of proteins, the enzymes act in the breakdown of peptide bonds, forming peptides and amino acids, which are more absorbable compounds.

So, to increase the rate of nutrient digestibility, the inputs undergo several hydrolysis processes, which may be chemical, enzymatic and thermal. The advantage of the industrial process of enzymatic hydrolysis is the greater preservation of amino acid integrity, due to the lower denaturation rate.

To test these results in practice, the “Use of Ezymatic Hydrolysate Ingredients For Animal Nutrition” study was presented by us at ILDEX Vietnam. It compared three different sources of protein in the evaluation of larval lobster performance in the early stages of development. The ingredients used were:

  • Intact fish meal (IFM);
  • Chemically denatured fish meal (DFM);
  • Fish meal that underwent enzymatic hydrolysis (HFM).

Check the chart below:

Gamble, S. Et Al (2015)

Source: GAMBLE, S. et al (2015)

In short, the study found that the survival rate, rate of weight gain of animals, final weight and daily frequency change of the batch evaluated was higher with the use of the ingredient that was subjected to enzymatic hydrolysis.

Chicken Protein Hydrolysed

Among the inputs submitted to enzymatic hydrolysis available in the market, the use of hydrolyzed chicken protein has been showing good results in the balance of diets. It is the result of the enzymatic hydrolysis of poultry meat, liver and viscera.

As a result, we have an ingredient produced with high technology due to the hydrolysis of the nutrients being carried out at low temperatures, which maintains the integrity and quality of its nutritional properties.

With this, there are hydrolyzed chicken proteins on the market that present impressive numbers like:

  • Maximum moisture content in 8%;
  • Total fat at 6%;
  • Mineral matter in 6%;
  • Minimum crude protein content in 75%;
  • Minimum of 90% of digestibility.
  • In a study conducted by BRF Ingredients in partnership with the State University of the West of Paraná, based on the in vivo test of Nile tilapia, it was observed that with the inclusion of hydrolyzed chicken protein in the diet, an increase of the palatability index when compared to the treatment control that consisted in the use of fish meal happened.

The evaluation parameters of the palatability index were:

  • Feed consumption;
  • Feed rejection rate;
  • Average time of capture of the first feed pallete by tilapia.

In the same study, it was also shown that in the treatment with the inclusion of hydrolysed chicken protein there were higher survival rates of the tilapia in the initial stage and increase in the final weight of the fish.

Thus, a greater palatability of the rations with hydrolyzed chicken protein guarantees (besides the advantages already mentioned) an increase in water quality.

Impact on water quality

As mentioned earlier, poor formulation of diets in intensive aquiculture also contributes to the pollution of aquatic environments.

The quality of inputs also influences intensive aquaculture. In addition to providing balanced and quality diets, the farmer should be aware of the population density of farms and the amount of feed provided. Foods supplied in excess, that is, above the appropriate amount for a certain number of animals, generate water pollution.

Regarding food quality, it is related to the processing of the feed, the proportion of nutrients and the quality of the nutrients contained in it. In relation to processing, the provision of pelleted or extruded feeds reduces their disintegration, dissolution and consequently their waste in the aquatic environment.

The proportion of protein and energy in the diet formulation should be considered. The highly protein foods, the not consumed and the excreted by fish can cause pollution of the environment by nitrogen in excess.

Another important factor is the quality of the nutrients. Nitrogen excretion by animals will be reduced with the use of ingredients containing high digestibility proteins and low phosphorus content.


Within the scope of research carried out for the advancement of animal nutrition, several studies that have been carried out demonstrate the benefits of the use of food submitted to enzymatic hydrolysis in the performance of animals in the productive sector. The process of enzymatic hydrolysis made in foods, such as meat and chicken offal, improves digestibility rates and can be used as a good alternative to conventional feeds such as fishmeal.