To align with societal demands, aquaculture needs to enhance its environmental performance by improving the environmental sustainability of its feeds. Towards this objective, novel formulations could be based on organic or circular economy-driven ingredients. This study aimed to evaluate the global warming potential of such non-conventional feeds and their effects on growth performance and health status of juvenile gilthead seabream (Sparus aurata) in grow-out conditions and after exposure to a challenge event (overcrowding).
Three isonitrogenous and isoenergetic experimental diets were formulated: a control (CTRL) commercial-like feed; an organic (ORG) diet based on ingredients compatible with organic certification and with limited inclusion of animal proteins; and an eco-efficient (ECO) feed using circular economy-driven subproducts and with limited inclusion of fishmeal. The Global Warming Potential (GWP) of each feed was calculated using the Life Cycle Impact Assessment (LCA) methodology. Diets were tested in triplicate during stage 1 (growth) for 9 weeks with a fish density of 2.5 kg/m3 and on stage 2 (challenge) with overcrowding for 2 weeks by increasing density to 12.5 kg/m3. At the end of Stage 1, fish were sampled for whole-body composition, as well as dissected for liver and anterior intestine samples in both stages (growth and challenge) for assessment of lipid peroxidation (LPO) and molecular biomarkers of the gut immune condition, oxidative status and epithelium integrity.
At the end of Stage 1, final body weight was higher in fish fed diets CTRL and ECO, than those fed with ORG (p=0.002). The FCR was significantly higher for ORG (p=0.046). The digestibilities of nutrients and energy were higher in CTRL and ORG, but lower for ECO (p < 0.03). Whole body composition was not affected by the dietary treatments (p>0.05). Diet ORG showed higher GWP, followed by ECO and CTRL. There were no statistical differences (p>0.05) regarding the LPO among treatments in the liver and anterior intestine of Stage 1 fish or between fish from both stages. The feeds only affected the relative expression of one gene related with intestinal adaptive immunity (igm) (p<0.001) and another with epithelium protection (muc13) (p=0.001) at the end of the growth trial.
This study suggests that while the organic feed may slightly reduce fish performance, it still demonstrated positive results. In addition, the diets did not exhibit significant impacts on fish oxidative status. These novel feeds and particularly the organic have a higher GWP associated. Thus, more research is needed on the effects of such feed concepts and other environmental impacts (e.g., resource consumption) to provide a more comprehensive evaluation.
This work has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 956129 “EasyTRAIN”. Additional funding was obtained from the Portuguese national funds from FCT – Foundation for Science and Technology through projects UIDB/04326/2020 (DOI:10.54499/UIDB/04326/2020), UIDP/04326/2020 (DOI:10.54499/UIDP/04326/2020) and LA/P/0101/2020 (DOI:10.54499/LA/P/0101/2020), as well as from “Pacto da Bioeconomia Azul” (Project No. C644915664-00000026) within the WP5 Algae Vertical, funded by Next Generation EU European Fund and the Portuguese Recovery and Resilience Plan (PRR).