Fishmeal is and has always been a big part of aquaculture feeds. Being a co-product of fished marine species that belong to some of the cultured species natural diets in the wild, fishmeal is the primary and closest-to-wild protein source in aquatic species farming.
 

Not only it is rich in amino acids that are highly digestible for farmed species, but also has a very attractive taste and smell for carnivorous species that can trigger innate predation behaviour, allowing a good feed intake of manufactured aquatic feeds.
 

But fishmeal use in feeds has declined over the years simultaneously to technologic development of aquaculture nutrition, passing from 70 percent of fish diets to around 10 to 20 percent of most of carnivorous species' diets today.
 

If fishmeal remains essential to diets and the best protein source on the market, its use as a resource faces availability issues for future feed demand meeting global demand of seafood products, as forage fish stocks are not unlimited, and catches have been declining in recent years.
 

This leads to two important issues in aquafeed production: sustainability (use of sustainable and traced ingredients that are not originating from over farmed fish stocks) and price, as fishmeal prices are very high at the moment.


Anticipating these problematics, industry and researchers have been investigating alternative solutions to fishmeal in order to optimise aquaculture diets and meet the demand from consumers up to 2050. If new proteins are showing high promises (insect meal, single-cell proteins), their development is still at an early stage and production capacities are not big enough to provide sufficient supply and cost-effective prices compared to other available protein sources.

 

The use of plant protein, which has been the most investigated topic alongside plant oils in aquaculture nutrition for the past-decade, is thus the only solution that can be currently considered at industry scale to replace fishmeal in feeds.


Considering plant protein are already an important part of nowadays aquaculture diets, their total substitution to fishmeal has been an issue, not only for digestibility rates, but also for taste of feeds, reducing palatability and consumption of feeds. It is thus essential to provide additional taste & attractivity solutions to feeds with replaced fishmeal to compensate palatability loss to fishmeal feeds, with sustainable ingredients.

 

A shrimp-specific solution
In this context, the Phodé Laboratories, a facility that specialises in neurosensorial solutions, has designed Olpheel Good, a shrimp-specific solution adapted to shrimp taste preferences and chemoreceptors to stimulate feed intake behaviour, consumption and appetite.


Indeed, appetite is often left out of calculations during feed monitoring, but it is a key point to feed intake. Also, feed intake has the same hormonal messengers to stress leading to satiation state; thus, a stressed animal will not have an appetite.

 

The effects of Olpheel Good have been tested in the Prince of Songkla University in Thailand on feed intake & stress response while included in High-fishmeal feeds (HFM) and Low-fishmeal feeds (LFM).


For each treatment, 50 shrimp were assigned to 220L tanks with 15 ppt brackish water, with four replicates per treatment. When both feeds contained around 35% of crude protein and 7% of carbohydrates, HFM feeds contained 20% fishmeal while LFM feeds contained 10% of fishmeal and an extra 10% of soybean meal and corn protein concentrate.

During these experiments, while global feed intake was measured after 8 weeks, two different behaviour tests have been implemented:

- A feed consumption speed test with a feeding tray left for 30 minutes in shrimp tanks; the quantity of feed eaten by 30 minutes was compared between all different treatments

- An acute stress inducing test by stirring water for 5 seconds and taking 12 shrimp out of water for evaluation of morphology and colour of antennae; immobility time was also measured after putting shrimp back in tanks


Significantly improved feed intake
As expected, treatments aside, global HFM feed intake was superior to LFM feed intake. The use of Olpheel Good significantly improved feed intake in HFM diets, and a tendency was observed in LFM diets. Also, the inclusion of Olpheel Good in LFM diets allowed a similar feed intake to control HFM diets.


Regarding consumption speed, it appeared that it is higher for shrimp fed with HFM diets compared to LFM diets. A tendency to higher consumption speed was observed with the use of Olpheel Good in both diets.


While no significant differences were observed between the two diets, the inclusion of Olpheel Good in both diets reduced significantly immobility time compared to the control.

 

While no significant differences were seen with the use of Olpheel Good with high-fishmeal, low-fishmeal treatment was clearly leading to an important stress as all shrimp displayed red antennae. The use of Olpheel Good allowed a return to normal antennae for 58.3% of the shrimp included.


A very interesting solution
The substitution of fishmeal in shrimp diets at a 10 percent rate by plant protein has led to losses in feed intake, but also to an increased stress behaviour displayed by shrimp after facing acute stress.


This parameter should be taken in consideration while formulating low-fishmeal feeds: diets could face nutritional requirements of shrimp, but besides low consumption resulting in feed waste and animals not assimilating the sufficient quantity of energy, this could lead to stressed and thus weaker animals in critical events like transfers/transportation which can result in diseases and mortalities.


The use of a neurosensorial additive, Olpheel Good, has stimulated feed intake by improving attractivity and palatability of feeds, but also appetite; by reducing stress induced messages and allowing shrimp to react quicker to an acute stressor.


This solution could be very interesting to complete LFM feeds which provide sustainable and cost-efficient shrimp nutrition in the coming years.

 

Note from the editor:
If you have enjoyed what you have read here, then why not treat yourself to a International Aquafeed magazine in-print subscription?

For a small fee, you too could join the many thousands of others who already receive content like this and more through their door very month.

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Article contributed by Amine Chaabane, Species & Product Manager - Aquaculture & Jean-François Gabarrou, Scientific Manager, Laboratoires Phodé, France.

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