Olive Pomace and Soybean-Sunflower Acid Oils as Alternative Fat Sources in European Seabass (Dicentrarchus labrax) Diets: Effects on Performance, Digestibility and Flesh Fatty Acid Composition and Quality Parameters

Abstract

The effects of dietary inclusion of soybean-sunflower and olive pomace acid oils on growth, digestibility and flesh composition were studied in European seabass. Eight diets were fed for 100 days (101.37 ± 0.33 g initial weight, mean ± SD), differing in the added fat source (25% fish oil, 75% experimental oil): S (crude soybean oil), SA (soybean-sunflower acid oil), O (crude olive pomace oil) or OA (olive pomace acid oil); 3 blends: S-O, S-OA, SA-OA at a 1:1 ratio; and a diet containing only fish oil (F) as a control. Animals fed OA showed the worst performance among dietary treatments, with the lowest weight, specific growth ratio, average daily gain and the highest feed conversion ratio (p < 0.01). In contrast, other diets including acid oils did not impair performance. Acid oil diets did not affect the apparent digestibility of dry matter, crude protein or total fatty acids (p > 0.05), but a lower digestibility of lipids and saturated fatty acids was observed (p < 0.001). Flesh composition and fatty acid profile were not affected by the high dietary free FA content (p > 0.05). Hence the results suggest that the studied acid oils may potentially be used in fish diets although further studies are needed.

Effect of Feeding Acid Oils on European Seabass Fillet Lipid Composition, Oxidative Stability, Color, and Sensory Acceptance

“…The aim of this work was to evaluate the effect of the partial replacement of FO in fish diets by AO instead of crude oils from two different vegetable sources (soybean and olive pomace) on lipid composition, oxidative stability, color, and sensory acceptance of fresh and refrigerated European seabass fillets. This study complements the information published by Verge-Mèrida et al [13] on growth and digestibility parameters of the same specimens used in the present work.…”

“…Remarkably, the recommendations published by FEDNA [27] for the use of AO in animal diets establish a total MIU value lower than 5%, which was fulfilled by the SAO and slightly exceeded by OPAO. In fact, in the performance parameters resulting from the experimental diets used in this work and that were reported by Verge-Mèrida et al [13], no effect was observed when SAO was used, but a significantly lower performance was found when fish were fed with OPAO diet, showing the lowest weight (226.22 g vs. the range of 244.45-250.20 g), specific growth rate (0.80%/day vs. the range of 0.88-0.90%/day), and average daily gain (1.25 g vs. the range of 1.43-1.49 g). Regarding the apparent digestibility of dry matter, crude protein, or total FA, no Aquaculture Nutrition effect was observed when AO were included in the diets [13].…”

“…In fact, in the performance parameters resulting from the experimental diets used in this work and that were reported by Verge-Mèrida et al [13], no effect was observed when SAO was used, but a significantly lower performance was found when fish were fed with OPAO diet, showing the lowest weight (226.22 g vs. the range of 244.45-250.20 g), specific growth rate (0.80%/day vs. the range of 0.88-0.90%/day), and average daily gain (1.25 g vs. the range of 1.43-1.49 g). Regarding the apparent digestibility of dry matter, crude protein, or total FA, no Aquaculture Nutrition effect was observed when AO were included in the diets [13]. Beyond this, to promote the upcycling of this type of refining by-products as vegetable feed fats to replace FO for aquaculture nutrition, it is important to comprehensively study their impact not only on fish performance parameters but also on the composition, oxidative stability, and sensory acceptability of the flesh, so that the interest of the various stakeholders (feed producers, farmers, and consumers) is addressed.…”

“…The five diets were randomly assigned to different tanks (three tanks per experimental diet), and the experimental feeding period lasted for 100 days. The effects of these diets on animal performance parameters have been published elsewhere [ 13 ].…”

“…Using AO as feed fats alternatively to other lipid sources is a way to upcycle them, which would contribute to improving aquaculture sustainability. However, there are only a few trials performed with these by-products in the literature, focusing mainly on their effects on lipid digestibility and productive parameters and showing controversial results [ 12 , 13 ]. In fact, as described by Varona et al [ 11 , 14 ], one disadvantage of AO is their high variability in various compositional parameters such as FFA content, insoluble impurities (I), or unsaponifiable matter (U).…”