Effects of Dietary Phenylalanine and Tyrosine Supplements on the Chronic Stress Response in the Seabream (Sparus aurata).

Natalia Salamanca,Oscar Moreno,Emilio Morales,Marcelino Herrera,Inmaculada Giráldez,Ignacio De La Rosa

doi:10.3389/fphys.2021.775771

Abstract

The increase of aquaculture production is associated with a growing interest in improving physiological status and welfare in fish. For this reason, the search for strategies for mitigating stress has been intensified, with one of these strategies being food supplementation with different amino acids (AA). The objective of this study was to evaluate the effects of dietary phenylalanine (Phe) and tyrosine (Tyr) supplements on the endocrine and physiological state of seabreams (Sparus aurata) subjected to chronic stress. The fish were stocked at 30 fish/tank in a recirculation aquatic system, fed one control diet and two diets supplemented with 5% Phe or Tyr for 90 days. Blood was drawn from 10 fish per tank every 30 days, and the weight and length were measured every 15 days. At the end of the experiment, length/weight of the fish were measured, and they were sacrificed for the extraction of blood, head kidney, liver, and brain. Classic plasma stress markers (glucose, lactate, proteins, and cortisol), as well as hormones derived from Phe and Tyr (adrenaline, norepinephrine, and dopamine) and the accumulation of AA were analyzed. Fish fed with diets supplemented with Phe or Tyr showed a reduction in various stress markers and physiological parameters. In addition, the stress condition favored a mobilization of AA toward the tissues, especially in supplemented diets, so this excess of AA could be used as an energy substrate to cope with stress.

Highlights

In recent years, aquaculture studies have focused on finding new strategies for minimizing stress and increasing animal welfare in the main species of interest, such as the gilthead seabream (Sparus aurata), whose culture is carried out in different marine farms along the Mediterranean and SouthAtlantic areas, both onshore and offshore (AGAPA, 2019)
The slope of the length curve was less than that of the fish subjected to stress and fed the same amino acid (Figure 1B)
Samples fed with amino acids (AA) and subjected to stress showed a significantly greater weight curve than those fed with the same amino acid within the basal state (Figures 1C,D)

Summary

Introduction

Aquaculture studies have focused on finding new strategies for minimizing stress and increasing animal welfare in the main species of interest, such as the gilthead seabream (Sparus aurata), whose culture is carried out in different marine farms along the Mediterranean and SouthAtlantic areas, both onshore and offshore (AGAPA, 2019). In 2020, the production of seabream in the world experienced a decrease of 1.3% compared to 2020, reaching 249,200 tons, according to statistics from APROMAR (2020) (Spanish Association of Aquaculturists). Seabream farms exist in 18 countries, the top producers being Turkey (33.7% of total production), Greece (25.9% of total production), and Spain (9.3% of total production). Effects of Amino Acids Supplements on the Chronic Stress production of seabream, it dropped off 9.4% in 2019, which represented an important decrease after the slight rebound occurred in 2017. The main Spanish region in seabream production is Valencia, which produces 49% of the total. Besides important growth and reproductive indexes, this species’ success relies on its high domestication level (Teletchea, 2015)

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Conclusion