Line of action:

Status:

Execution date:

General:

In vivo and in vitro evaluation of diets made with the new alternative ingredients in the ALTERNFEED project and study of their degree of sustainability.

Specific:

1. To study the digestibility of diets formulated in vivo and in vitro.

2. To assess the effect of diets on zootechnical parameters in trout and sea bass farming.

3. Study the environmental impact and the effect of the ingredients on the final composition of the waste generated during cultivation.

4. Give visibility to sustainable ingredients in aquaculture diets.

A.1 In vitro evaluation of the digestibility of diets

A.1.1 Fine-tuning of the enzyme deglisibility protocol

A.1.2 Cell line assays

A.2 Experimental validation of diets

A.2.1 Experimental validation in sea bass

A.2.2 Experimental validation in trout

A.3 Study of the sustainability of diets

A.3.1 Carbon footprint calculation

A.3.2 Estimation of the residual composition of diets

A.4 Communication and outreach

A.4.1 Communication: project visibility

A.4.2 Dissemination of results

A year after the start of ALTERNFEED, the working group created by ANFACO-CECOPESCA and CARTIF, this time together with IRTA, launched its second phase, ALTERNFEED II, with the aim of experimentally validating the feed developed in the first phase, in rainbow trout at the ANFACO-CECOPESCA facilities, and sea bass, at the IRTA facilities.

The experiments carried out in vivo have lasted 60 days and have shown that alternative feeds, with the substitution of part of fishmeal and fish oil for insect meal or the lipid and protein fraction of the cooking water of canned tuna, aim to be the most suitable, since they produce a growth similar to the control diets in trout and sea bass and have a greater use as they present a lower rate FISH-IN:FISH-OUT. Sea bass and trout fillets fed with the protein and lipid fraction of canned tuna cooking waters have a higher percentage of protein and omega 3 fatty acids, while sea bass and trout fillets fed with insect meal have more fat and, specifically, more omega 6 fatty acids. In addition, they are more environmentally viable, as they have a carbon footprint that can be improved compared to control diets.

The data of the results in vivo have been largely corroborated with the in vitro digestion experiments where, in the case of trout diets, a digestibility similar to the control of these two products and a worse rate of protein release by microalgae diets were observed. As for cell analyses, conclusive results could not be obtained due to technical problems in the development of cell culture.

During ALTERNFEED II, live experiments and in vitro studies were conducted to evaluate the effect of these alternative ingredients on trout and croaker, freshwater and marine fish, respectively. The data obtained have allowed the following conclusions to be drawn:

• There is a clear difference in the ease of hydrolyzing the protein present in the five feeds analyzed. This difference represents around 7% more hydrolysis in the control feed compared to the microalgae feed, with the rest showing intermediate values. This result only refers to the ease with which the protein is hydrolyzed by trout enzymes, but not to the nutritional quality of said protein (amino acid profile), so the results obtained may not have a direct relationship with the growth result obtained when using such feed.

Validation experiment

• Generally, alternative feeds allowed normal growth of croaker and trout during the development of both experiments. Although no significant difference between diets has been observed in sea bass, in trout it has been observed that the diets of microalgae and the mix have worse growth values.
• Sea bass and trout fillets fed with the protein and lipid fraction of canned tuna cooking waters have a higher percentage of proteins and omega 3 fatty acids, while those fed with insect meal have more fat and, specifically, more omega 6 fatty acids.
• Alternative diets have a higher degree of sustainability as they have a lower FISH-IN:FISH-OUT ratio than control diets. This data is quite promising, integrating the zootechnical and environmental efficacy of the product. In alternative diets, the FI:FO has been reduced by at least 15% compared to the control.
• The digestibility results indicate that both the protein and lipids of the different feeds were clearly digestible (ADC between 70-80% for protein and between 78-86% for lipids).
• In view of the results obtained, it seems that any of the diets analyzed could be used as an alternative source of protein in trout and sea bass farming, since there was no negative effect on growth, digestibility or immune system, except in the case of the microalgae diet in trout where it is necessary to adjust the inclusion percentage.
• As far as possible, it is recommended to expand the assay by trying to evaluate inflammatory markers in blood and to increase the number of markers to be analyzed, if possible, by gene expression.

Carbon footprint

To estimate the sustainability of the diet, the carbon footprint and residual estimation of the diets were calculated, according to the physicochemical parameters of the water and the residual composition of the diets.

• An interesting and competitive environmental potential of diets that include insect meal and protein and lipid fraction recovered from tuna cooking water is detected. Despite both having a larger carbon footprint than the control diet, they are interesting options, since by optimizing their obtaining processes (carried out at laboratory level in this project), their footprints may be smaller and, consequently, present as viable alternatives.
• It is concluded that the diet has a direct effect on the composition of the faeces and the mixed diet seems to be the most suitable to reduce the discharge of nitrogen and phosphorus in the tributaries. We consider it necessary to extend the study to confirm these results.

As for the dissemination of the project, in addition to the coordination and monitoring meetings, press releases and communications were disseminated through social networks and two informative videos were produced. Likewise, results were presented at two events (Business2Sea and the results transfer webinar organized by the entity). The project appeared in issues 136 and 140 of the journal Industria Conservera and was presented in a scientific abstract at the Aquaculture Europe congress on aquaculture, Sustainable products and canning industry by-products as ingredients in aquafeeds for juvenile products.