Abstract
Simple SummaryA number of recent studies have demonstrated the essentiality of dietary taurine in many commercially relevant cultured fish species. Taurine is involved in many physiological functions in fish and represents an essential nutrient, which exert powerful antioxidant properties and is required as a supplement in the feed when a relevant percentage of vegetable protein sources are utilized. Our results show that dietary taurine can reduce the oxidative status of marine fish under swim stamina stress conditions. These data could be essential for the development of diets with fishmeal/soybean meal substitutions in the effort to improve the sustainability of the aquaculture.Taurine (Tau) is an amino sulfonic acid, which is widely distributed in animal tissues, whereas it is almost lacking in plants with the exception of certain algae, seaweeds, and few others. In the aquafeed industry, Tau is mainly used as a feed additive to promote growth in marine fish species with limited cysteine sulfinate decarboxylase activity. In particular, Tau supplementation is required in feeds in which fishmeal (FM) is substituted with high percentages of plant-derived protein sources such as soybean meals (SBM) that have much lower levels of Tau than FM. In addition to being a growth promoter, Tau exert powerful antioxidant properties being a scavenger of the reactive oxygen species (ROS). Under sustained swimming conditions, an intracellular increase in ROS production can occur in fish red muscle where the abundance of mitochondria (the main site of ROS formation) is high. Accordingly, this study aimed at investigating the effects of dietary Tau on European seabass (Dicentrarchus labrax) growth and oxidative stress response induced by swimming exercise. Individually tagged fish of 92.57 ± 20.33 g mean initial weight were fed two experimental diets containing the same low percentage of FM and high percentage of SBM. One diet was supplemented with 1.5% of Tau. Tau supplemented in the diet had a positive effect on fish growth, and enhanced swimming performance and antioxidant status. Two swim endurance tests were performed during the feeding trial. Metabolic oxygen consumption (MO2) was measured during exercise at incremental swimming speeds (0.7, 1.4, 2.1, 2.8, 3.5, and then 4.2 BL (body length) s−1, until fatigue). Fish maximal sustainable swimming speed (Ucrit) was determined too. To investigate the antioxidant effect of dietary Tau, we also measured ROS production in fish blood by RBA (respiratory burst activity) assay and quantified the expression of genes coding for antioxidant enzymes by qPCR (quantitative polymerase chain reaction) , such as SOD (superoxide dismutase), GPX (glutathione peroxidase), and CAT (catalase) in red muscle and liver. There was a significant effect of Tau upon Ucrit during exercise. Additionally, ROS production was significantly lower in fish fed with Tau supplemented diet, supporting the role of Tau as ROS scavenger. The protective effect of Tau against oxidative stress induced by forced swimming was denoted also by a significant decrease in antioxidant enzymes gene expression in fish liver and muscle. Taken together these results demonstrate that Tau is beneficial in low FM-based diets for seabass.
Highlights
Fishmeal (FM) supplies are declining and the aquaculture sector is urgently searching for alternative sources of protein
To investigate the antioxidant effect of dietary Tau, we measured reactive oxygen species (ROS) production in fish blood by respiratory burst activity (RBA) assay and quantified the expression of genes coding for antioxidant enzymes by qPCR, such as superoxide dismutase (SOD), GPX, and CAT in red muscle and liver
Effect of Taurine on the Fish Performance Parameters and on the Metabolic Response. Diet, and their interaction as sources of variation, the increase in fish body weight (BW) from t1 through the end of the trial, showed statistical differences due to the factor diet (p < 0.01), being higher in fish fed a 1.5% Tau-supplemented diet than in the control group (Table 2)
Summary
Fishmeal (FM) supplies are declining and the aquaculture sector is urgently searching for alternative sources of protein. The use of SBM has given positive results in marine fish feeds, the presence of anti-nutritional factors, and the scarcity of indispensable amino acids such as methionine and lysine, has reduced fish performance. Another reason for the decrease in growth in fish fed plant-protein-based diets is the lack of the amino sulfonic acid taurine (Tau), which is an organic compound abundant in FM and other animal-based feeds [2]. Tau is widely distributed in animal tissues, whereas it is almost lacking in plants with the exception of certain algae, seaweeds, and a few others, such as cactus pear
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