by Pierre Fortin, Aquaculture Nutritionist, Aquanéo, Techna France Nutrition, France

Protein is a major cost in aquafeed as aquatic animals have high protein needs compared to terrestrial animals. Furthermore, fishmeal is very often used in fish and shrimp diets. Its price increases faster than other ingredients. Over a 25 years period, fishmeal price increased by 350 percent, while soybean increased only by 150 percent (Source: Indexmundi).

In this situation, feed producers need to be careful when using protein sources to fulfil the needs of the animals. First from an economic point of view, but also regarding the quality of this protein. Indeed, protein itself doesn't mean a lot, protein could have a low digestibility (because of intrinsic composition of an ingredient, or suffer from processing for eg), it could also be unbalanced. This could result in lower growth of the animal. This brief article will help you save some cost on your feed while safeguarding its quality.

The quality of feed relies on the quality of its ingredients

'Quality inputs lead to quality outputs', this saying is also true for feed. If one doesn't watch what they buy or doesn't handle it properly; even fish meal could be of a lower quality than vegetable ingredients. It depends on the raw material quality, is it processed fresh, how is it cooked and dried, extracted, protected and finally stored? These key points are similar for quite a lot of ingredients. Therefore, analysis can give a good overview of the quality of ingredients. Specific criteria exist for each raw material.

Some important analysis to ensure the quality of several ingredients

For example, fishmeal quality could be impacted before processing if the fish are not stored properly; this will be evaluated by the biogenic amines values which are the result of degradation of specific amino acids. Processing could also have an impact on the quality of the product by overcooking; this could be evaluated by oxidative parameters. Overall quality of the proteins within fishmeal is often evaluated by pepsin digestibility.

Similar parameters could be analysed on animal meals such as poultry meal, meat and bone meal. For soybean meal, different tests exist such as the urease test and anti-trypsic factors. They will analyse the processed well-cooked protein, with enhanced digestibility, which, if subject to overcooking, may result in lower digestibility of certain sensitive amino acids such as lysine. Free lysine could also be an indicator of the quality of DDGS. The main risk with these products is overcooking which reduces the overall digestibility. 

Beyond protein: Digestibility and amino acid profile to fulfil each species needs

Once your raw materials are sourced, analysed and validated, the second step is to know if they are digestible by the target animals. Digestibility of protein depends on several factors, but mainly depends upon the type of raw material. The amino acid chain, branching with other compounds such as carbohydrates, affects the way fish or shrimp enzymes are able to digest the material. As an example, fishmeal digestibility is affected by ash content: the more ash there is, the less digestible it will be (but this is not the only parameter to take into consideration).

Within the various vegetable protein sources existing in the world, some are more digestible than others. Some of the more readily digestible ones will be soybean, peas and beans, whereas coprah, alfalfa or linseed will be among the least digestible ones. Another parameter to consider is what part of the initial raw material is in the final product.

Indeed, when extracting different parts of a seed, protein digestibility may change. For example, wheat grain or wheat flour, which are roughly the whole grain, almost have the same digestibility. However, when considering wheat bran, digestibility will be reduced as this part of the grain contains more fibre affecting the overall protein quality. Wheat gluten meal (80% protein) is more digestible than wheat gluten feed (20% protein) which is more digestible than wheat grain. Similar patterns will also occur in other plant products, or in animal proteins.

Aquanéo, the aquaculture brand of Techna, has been acquiring this knowledge over several years of experience and integrated this specific information in its own formulation matrix. In the end, it will be used to ensure feed quality while formulating at the lowest cost for our customers.

Another aspect to take into consideration is amino acid profile. This is usually quite stable within vegetable products but can be prone to fluctuations within fishmeal or animal proteins depending on the species and part of the animal being processed (whole, trimmings, feather, blood, meat, bones etc). Amino acid profile analysis should be performed on these fluctuating ingredients.

We can see that amino acid profiles are very different according to raw material. For example, using wheat and corn products as protein replacers may create lysine deficiency as their Lysine/Protein ratio is around two percent compared to fishmeal which is usually above six percent total protein. Once again, all of this crucial information is part of Aquanéo's formulation matrix and will be used to prepare the feed recipe. Furthermore, Aquanéo's lab offers the analysis of amino acid profile of raw materials.

All the above mentioned will provide a good overview of the quality of different raw materials available. Now the formulation can fulfil the requirements of the targeted animal, not only by adding a certain amount of nitrogen, but also by taking into account the quality and digestibility of protein, plus its amino acid profile.

Economix: An interesting solution to reduce costs and improve protein utilisation

As mentioned at the beginning, protein is a major cost for most feeds for aquaculture, but ways exist to reduce this cost, such as focussing upon on the overall digestibility of feed. Indeed, specific additives like Economix, developed by Aquanéo, can help the animal's digestive system to increase the digestibility of protein and, therefore, support the performance of the animal.

Results of a trial done in SPAROS Portugal on seabream (115g) showed an increase in protein digestibility from 93.8 percent up to 94.3 percent with the use of Economix. It also dispayed an important increase in methionine digestibility from 87.9 percent to 91.7 percent. In the Economix formula, crude protein level was reduced by one percent, but keeping the same digestible protein (38.5% in Aquanéo's formulation matrix) and same amino acid profile. Composition of the feeds was very similar, but we replaced two percent fishmeal from the control formula. Fish meal was replaced mainly by wheat, monocalcium phosphate and Economix. The use of this additive allowed a cost reduction of €12.4/mt on a typical Mediterranean fish feed while improving the digestibility and keeping the same performances.

Another trial was done on 90g trout with a top coating of the Economix on a standard commercial feed and a vegetable feed (no fish meal or oil). Results showed an increased weight gain and decreased feed conversion ratio (FCR) at the end of the trial. In addition, results also observed a lower abdominal fat notation, most likely coming from the fact that protein was better utilised and less energy was deposited in the viscera. In this last case, using Economix could save on the feeding cost up to €3/mt of fish. (Extra cost - Better performances = Gain).

Economix reduces the cost of feed while keeping feed quality and fish performance optimised. The solution could be used with simple ingredient substitution (-2% Fishmeal => +1% Soybean +0.8% Cereal + 0.2% Economix) or with a reformulation through its valorisation matrix.

Shall you require more information on Aquanéo's support regarding analysis, formulation or Economix, please contact us on: contact@techna.fr or visit our website

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