22
Table 4. Fatty acid composition levels in muscle lipid of rainbow trout juveniles fed experimental diets containing fresh fish oil (CTL) and tuna oil byproducts at a constant temperature of 17°C ±1°C for 12 weeks.
3 weeks CTL
12 weeks
Dietary Treatment
Tuna oil byproduct
CTL
Tuna oil byproduct
Dry matter (%)
Total lipid (% wet weight) 5.7±1
FA composition (% total FA)
EPA 4.5±0,6 2.4±0.2
DHA 5±0,9b 7.2±1,2a 4.9±1,2b 8,9±1,7a
Unsaturation index 138±9 137±10 129±10 137±15
24.4±1.1 24.5±0.7 26.2±1,4 25,4±0,7ab a
5.3±0.7
6.9±1,1a 6±0,7b
a
5±0,4a 2,4±0,3b
Values are means ± SD. Within rows and for each sampling time, means not sharing a common superscript letter (a,b) are significantly different (p< .05) according to one-way ANOVA followed by a Newman-Keuls test.
cooked from the cannery process. Their potential higher oxidative status expressed by parameters such as anisidine (AV) and peroxide value (PV) of cooked byproducts has been studied by Fontagne et al., 2018. A 12-week trial was conducted on juvenile rainbow trout (initial weight 62±1 g) up to portion market size, fed with diets (iso-energy, crude protein 48%, crude lipid 23%) supplemented either with 15% standard capelin oil (CTL) or tuna oil from byproducts (BYP) as described in Table 2. At the end of the experimental period, no significant differences in growth performance were recorded between dietary groups as shown in Table 3. Furthermore, muscle lipid content exhibits significant DHA differences in line with initial fatty acid compositions of tuna oil (Table 4).
Tuna oil sustainability Worldwide, the tuna industry presents a case study in valorization. Tuna byproducts are transformed into fishmeal and fish oil (FMFO) across the world, ensuring that there is 100% utilization of fish that are caught. It is estimated that over 60% of total worldwide catches of tuna (nearly five million tons a year) are transformed in processing plants and nearly 50% of these tonnages generate byproducts which are in turn processed into tuna FMFO. MarinTrust certification applies to most major suppliers. The Forage Fish Dependency Ratio (FFDR) for species such as salmon is under scrutiny. It should be underlined that byproducts such as tuna are not taken into account in the FFDR. The last ASC feed salmon standards
requested a FFDR to oil below 2.52 with new requests from some food retailers to go below 1.75. Finally, in terms of safety and contamination from undesirable substances such as heavy metals or dioxins/PCBs, most tuna oils contain levels far below maximum limits set by the actual EU regulations.
Conclusion Fish oils from byproducts of the tuna fishing industry represent highly valuable sources of n-3 LC-PUFA which can help the aquaculture industry maintain its profitability and product nutritional quality in a sustainable strategy. References available on request
More information: Dominique Corlay Consultant Aquaculture Natural Solutions, France E: ansaqua.dc@gmail.com
Charles Davy Advisor Marine Biotechnology Products, Mauritius E: cdavy@mbp.mu
Aquafeed: Advances in Processing & Formulation Vol 12 Issue 3 2020