Inclusion of alternative marine by-products in aquafeeds with different levels of plant-based sources for on-growing gilthead sea bream (Sparus aurata, L.): effects on digestibility, amino acid retention, ammonia excretion and enzyme activity

Abstract

The search for new sustainable aquafeeds for the species with greater economic importance, such as the gilthead sea bream in Europe, is one of the main challenges in the aquaculture sector. The present work tested fishmeal replacement by a mixture of plant meals at different levels, as well as the use of marine by-products with attractant properties and high-quality protein in high plant protein diets. In order to do that, effects on growth and biometric parameters, digestibility, amino acid retention, excreted ammonia and proteases and amylase activity were assessed, using six different diets: FM100 (100% of protein provided by fishmeal), FM50 (50% of replacement), FM25 (75% of replacement) and FM0 (100% of replacement), but also FM25+ (75% of replacement and 15% of squid and krill meal inclusion), and FM0+ (100% of replacement and 15% of squid and krill meal inclusion). In group FM0, a clear impact of dietary changes was observed on growth, survival and ammonia excretion. Amino acid retention in group FM0+ was also significantly affected, which can be explained by the limited content of certain amino acids in this diet. On the other hand, no significant differences were observed in most biometric parameters or in enzyme activity. In conclusion, complete fishmeal replacement can be achieved by using a mixture of plant-based sources, but supplementation with complementary marine ingredients can prevent detrimental effects on growth, survival, nutritional parameters and protein metabolism.

Impact of high dietary plant protein with or without marine ingredients in gut mucosa proteome of gilthead seabream (Sparus aurata, L.)

“…The present assay reported significant differences in weight, specific growth rate and other biometric indices, indicating a negative effect of total fishmeal replacement on growth performance of gilthead seabream. In previous trials, total fishmeal replacement has been successfully achieved for gilthead seabream without affecting fish growth [44].…”

“…Ingredients and proximate composition of the experimental diets are shown in Table 1. **Digestible values have been estimated using the apparent digestibility coefficients obtained from a previous digestibility trial [44].…”

“…Digestible essential and non-essential amino acids content of different diets (Table 2) were obtained from individual amino acids coefficients from a previous trial [44].…”

“…Proteome alterations on gut, skin or even plasma proteome caused by high dietary plant protein inclusion have been reverted thanks to some dietary additives, such as Candida utilis yeast [41] or sodium butyrate [38], in turns improving the fish performance and the immune status [42,43]. In this sense, marine alternative ingredients with potential functional properties, such as krill and squid meal, can be an interesting option to improve plant-based diets for carnivorous fish, reducing the inclusion of synthetic dietary supplements such as synthetic amino acids or minerals, and providing an optimal nutrient efficiency and economic profit ratio [44].…”

Effect of fish oil replacement and probiotic addition on growth, body composition and histological parameters of yellowtail (Seriola dumerili)

“…It is also known that the use of probiotics in diets can modified in the microbiota associated with the gastrointestinal tract of the host and generate beneficial effects such as increased feed conversion and digestibility (De Schrijver & Ollevier, 2000; Ten Doeschate & Coyne, 2008; Díaz & Martínez‐Silva, 2009, Je et al., 2019). Stress and immunosuppression in fish fed non‐fish meal and non‐fish oil are subjected to increase the chances that the fish will be affected by pathogens specially in liver (Martin & Król, 2017; Montero et al., 2008), since when marine ingredients replacement are high, mortality increases (Estruch, et al., 2018; Estruch, et al., 2018; Monge‐Ortiz, et al., 2018; Monge‐Ortiz, et al., 2018). In order to improve the survival of fish fed with high vegetal ingredients dietary inclusion and its effect on immunosuppression, probiotics can be added with the objective to enhance the immune system of depressed fish (Dimitroglou et al., 2011; Merrifield & Ringø, 2014; Ringø, 2020).…”