Aquaculture: why replace fish oil with animal oil?

In aquaculture, without any doubt, animal feed represents the largest portion of production cost.

The formulated feed for aquatic animals has as one of its main ingredients fish oil which, in addition to having high digestibility, also provides essential fatty acids for the proper animal development.

Although nutritionally well accepted source of fatty acids, fish oil faces environmental, ethical and economic issues related to its cost and availability.

Due to this, changes in the formulation of feed for aquaculture need to happen. But what type of oil/fat can be used as a rich source of fatty acids at a reasonable price and that is highly available?  Oils and fats from animals are the perfect option for this.

But what are the reasons that make this alternative viable?

Price and availability

Projections about the availability of fish oil are alarming. Reports suggest that, within a decade, the demand for this oil can exceed its supply.

The reduction in the availability of fish oil is associated with its high demand due to the growth of aquaculture. The imbalance of this scale also affects the price of this ingredient, which has become increasingly expensive over the years.

On the other hand, animal fats cost half the price of fish oil, or even less in some cases.

In addition to being widely available, it is estimated that it’s possible to reduce fabrication cost of feed for aquaculture by US$ 3.00/ton for each 1% of fish oil that is replaced by animal fat in its formulation. Analyzing only the economic part, using the animal’s oils in aquaculture would be already advantageous. However, a cheap ingredient doesn’t always represent being the best. Therefore, take a look the other advantages of animal’s oils:

Feed quality: resistance to oxidation and digestibility

The resistance to oxidation is directly related to the presence and quantity of unsaturation present in the structure of the fatty acids that make up a material.

Fish oil is mostly unsaturated and therefore highly susceptible to oxidation, which leads to a loss of both nutritional and sensory quality while in storage.

On the other hand, animal fats have few unsaturated fatty acids. Therefore, they are more resistant and stable, contributing to a greater expiry date. In nutritional terms, it is important for the components that are part of the feed to have a high digestibility.

That is, that they are appropriately used by the animal’s organism, with high absorption rate. In this matter, both fish oil and poultry oil provide high digestible energy to the cultured aquatic organisms.

A study suggested that the digestibility of animal fats is related to the water temperature where the animals are raised. For example, pork fat increases its apparent digestibility coefficient from 70% at a temperature of 5 °C to 78% at a temperature of 15 °C.

This effect happens because the animal fats have a higher melting point than oils. Such as fish oil for example, not much affected by the temperature variation of the water.

This way, when formulating feed for aquatic animals using animal fat, it is important to maintain a balance between saturated fatty acids and unsaturated ones (monounsaturated and polyunsaturated) and to consider the requirements and habitats of the different species.

It is estimated that the saturated content should not exceed 35-40% of the formulation, to ensure optimum digestibility.

The effect of fatty acids balance on animal performance

A study had put together a series of experiments that analyzed the performance and the growth of aquatic animals fed with feed containing animal fat and noted the importance of balancing fatty acid contents.

In general, when animal fat is limited to a maximum of 50% of the total content of lipids that are part of a feed, there is no occurrence of negative effects on animal performance. Also, no damage was found in their reproductive capacity.

Therefore, feed that has in its composition a balance between saturated fatty acids from animal fat, and mono and polyunsaturated fatty acids, are capable of promoting a healthy growth at a lower cost when compared to the exclusive use of fish oil.

Immune response

Anomalies in the immune system of the aquatic animals can occur if the balance of essential fatty acids is not reached in the diet.

There must be a balance between the ingested quantity of omega-6 and omega-3 fatty acids. Both are hormone precursors that regulate the immune response in the organism of animals.

Therefore, the lack of any of them would be a factor for the occurrence of an imbalance of the immune system.

Quality of aquatic animals

Due to the difference in the profile of animal fat and fish oil fatty acids, there is concern that animal fat will promote a change in the body composition of animals.

This type of phenomenon is likely to occur is some species. However not all the fatty acids consumed in the diet will be deposited in the muscle tissue of animals.

Therefore, by incorporating a controlled quantity of animal fat into the feeds, a marginal effect is expected on the body composition of the animals. This information is relevant mainly for fish with low body fat content.

What are the types of animal fat that can be used in aquafeed?

The options are endless. However, two of them stand out due to the low price, the high availability and the quality.

Poultry oil

Poultry slaughter generates by-products that, after cooking, can be pressed to obtain their lipid fraction, also known as poultry oil. This oil can also be extracted from the meal resulted from these by-products.

Poultry oil is a great source of essential fatty acids! Especially omega-6 and 9, contributing to a healthy balance of the lipid fraction in the diet.

Due to the use of fresh raw material and a mild cooking process, these oils are also able to contribute positively to the palatability of feed, making them well accepted by animals and not accumulated as waste at the bottom of breeding grounds.

A study tested different contents of poultry meal in feeds to replace fish meal in the diet of trout and concluded that a replacement of up to 33% presents no negative effect on weight gain and fish development.

Fat from pork and pork crackling meal

Pork fat comes from cooking, draining, pressing and/or centrifugation of by-products from pig slaughter. As a source of B vitamins and minerals, this fat contributes to the already mentioned balance of fatty acids that the diet of aquatic animals must have. Since 60% of its fatty acids profile is composed of oleic acid, which is monounsaturated.

With a similar composition of fatty acids, the pork crackling meal fat is obtained by cooking, pressing and centrifugation of the pork crackling, separating the protein fraction from the lipid fraction.

Both fats are produced with fresh and high quality raw material and go through mild heat treatments. Avoiding the development of oxidation processes, guaranteeing quality, stability and high shelf life.

Conclusion

The by-products of poultry and pig slaughter also have an extremely nutritious fraction that can be used in the feed of aquatic animals. Using animal’s oils in aquaculture as a substitute for fish oil can cause a positive impact on the cost and quality of products.

However, it is necessary to always be aware of the final proportion of fatty acids that the feed will have. As well as the availability of essential fatty acids and the digestibility of the nutrients present.