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

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.

Use of tissue chromogranin A as chronic and acute stress marker in fish

“…The catecholamines are released and cleared quickly in the bloodstream during stress conditions, hence sometimes these are not reliable stress indicators (Barton, 2002). However, recent studies have demonstrated that they can be useful linked to other indicators if a suitable sampling methodology is followed (Salamanca et al, 2021(Salamanca et al, , 2022. In our work, plasma adrenaline grew significantly after stress, confirming the stress status, as the cortisol variations pointed out previously.…”

Use of modern geometric design of fish ponds to increase welfare and blood parameters

“…And lead to lower WBC counts 37 . As well as nutrition, animals not fed a healthy diet may be more likely to develop infections 38 , which can lead to higher WBC counts 39 . Also, infection: Animals infected with a disease may have higher WBC counts as the body tries to fight off the infection.…”

Fish Responses to Alternative Feeding Ingredients under Abiotic Chronic Stress

“…Under chronic stress, Phe enriched diet in Gilthead seabream ( Sparus aurata ) decreases cortisol levels but decreases fish growth. Authors suggest an unbalanced diet (amino acid excess) results in malnutrition and reduced growth [ 41 ]. Including amino acids guarantees positive effects on fish growth during chronic stress.…”

“…In normal conditions, most lactate is produced by the erythrocytes; however, during intense physical activity, the muscle produces large amounts of lactate because of insufficient muscle oxygenation [ 47 ]. Salamanca et al (2022) showed the reduction of lactate in Sparus aurata subjected to chronic stress and fed with a Phe-enriched diet [ 41 ]. Additionally, Herrera et al, 2020 showed the same effect of Trp-enriched diets in Argyrosomus regius [ 38 ] ( Table 2 ).…”